<!--
     The FreeBSD Documentation Project

     $FreeBSD$
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<chapter id="disks">
  <title>Storage</title>

  <sect1 id="disks-synopsis">
    <title>Synopsis</title>


    <para>This chapter covers the use of disks in FreeBSD.  This
      includes memory-backed disks, network-attached disks, and
      standard SCSI/IDE storage devices.</para>

    <para>After reading this chapter, you will know:</para>
    <itemizedlist>
      <listitem><para>The terminology FreeBSD uses to describe the
      organization of data on a physical disk (partitions and slices).</para>
      </listitem>
      <listitem><para>How to add additional hard disks to your system.</para>
      </listitem>
      <listitem><para>How to set up virtual file systems, such as memory
      disks.</para></listitem>
      <listitem>
	<para>How to use quotas to limit disk space usage.</para>
      </listitem>
      <listitem>
	<para>How to encrypt disks to secure them against attackers.</para>
      </listitem>
      <listitem>
	<para>How to create and burn CDs and DVDs on FreeBSD.</para>
      </listitem>
      <listitem>
        <para>The various storage media options for backups.</para>
      </listitem>
      <listitem>
        <para>How to use backup programs available under FreeBSD.</para>
      </listitem>
      <listitem>
        <para>How to backup to floppy disks.</para>
      </listitem>
      <listitem>
        <para>What snapshots are and how to use them efficiently.</para>	
      </listitem>
    </itemizedlist>
  </sect1>

  <sect1 id="disks-naming">
    <title>Device Names</title>

    <para>The following is a list of physical storage devices
      supported in FreeBSD, and the device names associated with
      them.</para>

    <table id="disk-naming-physical-table">
      <title>Physical Disk Naming Conventions</title>

      <tgroup cols="2">
	<thead>
	  <row>
	    <entry>Drive type</entry>
	    <entry>Drive device name</entry>
	  </row>
	</thead>
	<tbody>
	  <row>
	    <entry>IDE hard drives</entry>
	    <entry><literal>ad</literal></entry>
	  </row>
	  <row>
	    <entry>IDE CDROM drives</entry>
	    <entry><literal>acd</literal></entry>
	  </row>
	  <row>
	    <entry>SCSI hard drives and USB Mass storage devices</entry>
	    <entry><literal>da</literal></entry>
	  </row>
	  <row>
	    <entry>SCSI CDROM drives</entry>
	    <entry><literal>cd</literal></entry>
	  </row>
	  <row>
	    <entry>Assorted non-standard CDROM drives</entry>
	    <entry><literal>mcd</literal> for Mitsumi CD-ROM,
	      <literal>scd</literal> for Sony CD-ROM,
	      <literal>matcd</literal> for Matsushita/Panasonic CD-ROM
		<footnote>
		  <para>The &man.matcd.4; driver has been removed
		    in FreeBSD&nbsp;4.X branch since October 5th,
		    2002 and does not exist in FreeBSD&nbsp;5.0 and
		    5.1 releases.  However this driver is back in the
		    FreeBSD&nbsp;5.X branch since June 16th,
		    2003.</para>
		</footnote>
	    </entry>
	  </row>
	  <row>
	    <entry>Floppy drives</entry>
	    <entry><literal>fd</literal></entry>
	  </row>
	  <row>
	    <entry>SCSI tape drives</entry>
	    <entry><literal>sa</literal></entry>
            </row>
	  <row>
	    <entry>IDE tape drives</entry>
	    <entry><literal>ast</literal></entry>
	  </row>
	  <row>
	    <entry>Flash drives</entry>
	    <entry><literal>fla</literal> for &diskonchip; Flash device</entry>
	  </row>
	  <row>
	    <entry>RAID drives</entry>
	    <entry><literal>aacd</literal> for &adaptec; AdvancedRAID,
	      <literal>mlxd</literal> and <literal>mlyd</literal>
	      for &mylex;,
	      <literal>amrd</literal> for AMI &megaraid;,
	      <literal>idad</literal> for Compaq Smart RAID,
	      <literal>twed</literal> for &tm.3ware; RAID.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>
  </sect1>
    
  <sect1 id="disks-adding">
    <sect1info>
      <authorgroup>
	<author>
	  <firstname>David</firstname>
	  <surname>O'Brien</surname>
	  <contrib>Originally contributed by </contrib>
	</author>
      </authorgroup>
      <!-- 26 Apr 1998 -->
    </sect1info>

    <title>Adding Disks</title>

    <indexterm>
      <primary>disks</primary>
      <secondary>adding</secondary>
    </indexterm>

    <para>Lets say we want to add a new SCSI disk to a machine that
      currently only has a single drive.  First turn off the computer
      and install the drive in the computer following the instructions
      of the computer, controller, and drive manufacturer.  Due to the
      wide variations of procedures to do this, the details are beyond
      the scope of this document.</para>

    <para>Login as user <username>root</username>.  After you have installed the
      drive, inspect <filename>/var/run/dmesg.boot</filename> to ensure the new
      disk was found.  Continuing with our example, the newly added drive will
      be <devicename>da1</devicename> and we want to mount it on
      <filename>/1</filename> (if you are adding an IDE drive, the device name
      will be <devicename>wd1</devicename> in pre-4.0 systems, or
      <devicename>ad1</devicename> in most 4.X systems).</para>

    <indexterm><primary>partitions</primary></indexterm>
    <indexterm><primary>slices</primary></indexterm>
    <indexterm>
      <primary><command>fdisk</command></primary>
    </indexterm>

    <para>Because FreeBSD runs on IBM-PC compatible computers, it must
      take into account the PC BIOS partitions.  These are different
      from the traditional BSD partitions.  A PC disk has up to four
      BIOS partition entries.  If the disk is going to be truly
      dedicated to FreeBSD, you can use the
      <emphasis>dedicated</emphasis> mode.  Otherwise, FreeBSD will
      have to live within one of the PC BIOS partitions.  FreeBSD
      calls the PC BIOS partitions <emphasis>slices</emphasis> so as
      not to confuse them with traditional BSD partitions.  You may
      also use slices on a disk that is dedicated to FreeBSD, but used
      in a computer that also has another operating system installed.
      This is to not confuse the <command>fdisk</command> utility of
      the other operating system.</para>

    <para>In the slice case the drive will be added as
      <filename>/dev/da1s1e</filename>.  This is read as: SCSI disk,
      unit number 1 (second SCSI disk), slice 1 (PC BIOS partition 1),
      and <filename>e</filename> BSD partition.  In the dedicated
      case, the drive will be added simply as
      <filename>/dev/da1e</filename>.</para>

    <sect2>
      <title>Using &man.sysinstall.8;</title>
      <indexterm>
        <primary><application>sysinstall</application></primary>
        <secondary>adding disks</secondary>
      </indexterm>
      <indexterm>
	<primary>su</primary>
      </indexterm>
      <procedure>
	<step>
	  <title>Navigating <application>Sysinstall</application></title>

	  <para>You may use <command>/stand/sysinstall</command> to
	    partition and label a new disk using its easy to use menus.
	    Either login as user <username>root</username> or use the
	    <command>su</command> command.  Run
	    <command>/stand/sysinstall</command> and enter the
	    <literal>Configure</literal> menu.  Within the
	    <literal>FreeBSD Configuration Menu</literal>, scroll down and
	    select the <literal>Fdisk</literal> option.</para>
	</step>

	<step>
	  <title><application>fdisk</application> Partition Editor</title>
	  <para>Once inside <application>fdisk</application>, we can type <userinput>A</userinput> to
	    use the entire disk for FreeBSD.  When asked if you want to
	    <quote>remain cooperative with any future possible operating
	      systems</quote>, answer <literal>YES</literal>.  Write the
	    changes to the disk using <userinput>W</userinput>.  Now exit the
	    FDISK editor by typing <userinput>q</userinput>.  Next you will be
	    asked about the Master Boot Record.  Since you are adding a
	    disk to an already running system, choose
	    <literal>None</literal>.</para>
	</step>

	<step>
	  <title>Disk Label Editor</title>
	  <indexterm><primary>BSD partitions</primary></indexterm>

	  <para>Next, you need to exit <application>sysinstall</application>
            and start it again.  Follow the directions above, although this
            time choose the <literal>Label</literal> option. This will
	    enter the <literal>Disk Label Editor</literal>.  This
	    is where you will create the traditional BSD partitions.  A
	    disk can have up to eight partitions, labeled
	    <literal>a-h</literal>.
	    A few of the partition labels have special uses.  The
	    <literal>a</literal> partition is used for the root partition
	    (<filename>/</filename>).  Thus only your system disk (e.g,
	    the disk you boot from) should have an <literal>a</literal>
	    partition.  The <literal>b</literal> partition is used for
	    swap partitions, and you may have many disks with swap
	    partitions.  The <literal>c</literal> partition addresses the
	    entire disk in dedicated mode, or the entire FreeBSD slice in
	    slice mode.  The other partitions are for general use.</para>

	  <para><application>sysinstall</application>'s Label editor
	    favors the <literal>e</literal>
	    partition for non-root, non-swap partitions.  Within the
	    Label editor, create a single file system by typing
	    <userinput>C</userinput>.  When prompted if this will be a FS
	    (file system) or swap, choose <literal>FS</literal> and type in a
	    mount point (e.g, <filename>/mnt</filename>).  When adding a
	    disk in post-install mode, <application>sysinstall</application>
	    will not create entries
	    in <filename>/etc/fstab</filename> for you, so the mount point
	    you specify is not important.</para>

	  <para>You are now ready to write the new label to the disk and
	    create a file system on it.  Do this by typing
	    <userinput>W</userinput>.  Ignore any errors from
	    <application>sysinstall</application> that
	    it could not mount the new partition.  Exit the Label Editor
	    and <application>sysinstall</application> completely.</para>
	</step>

	<step>
	  <title>Finish</title>

	  <para>The last step is to edit <filename>/etc/fstab</filename>
	    to add an entry for your new disk.</para>
	</step>
      </procedure>
    </sect2>

    <sect2>
      <title>Using Command Line Utilities</title>

      <sect3>
	<title>Using Slices</title>

	<para>This setup will allow your disk to work correctly with
	  other operating systems that might be installed on your
	  computer and will not confuse other operating systems'
	  <command>fdisk</command> utilities.  It is recommended
	  to use this method for new disk installs.  Only use
	  <literal>dedicated</literal> mode if you have a good reason
	  to do so!</para>

	<screen>&prompt.root; <userinput>dd if=/dev/zero of=/dev/da1 bs=1k count=1</userinput>
&prompt.root; <userinput>fdisk -BI da1</userinput> #Initialize your new disk
&prompt.root; <userinput>disklabel -B -w -r da1s1 auto</userinput> #Label it.
&prompt.root; <userinput>disklabel -e da1s1</userinput> # Edit the disklabel just created and add any partitions.
&prompt.root; <userinput>mkdir -p /1</userinput>
&prompt.root; <userinput>newfs /dev/da1s1e</userinput> # Repeat this for every partition you created.
&prompt.root; <userinput>mount /dev/da1s1e /1</userinput> # Mount the partition(s)
&prompt.root; <userinput>vi /etc/fstab</userinput> # Add the appropriate entry/entries to your <filename>/etc/fstab</filename>.</screen>

	<para>If you have an IDE disk, substitute <filename>ad</filename>
	  for <filename>da</filename>.  On pre-4.X systems use
	  <filename>wd</filename>.</para>
      </sect3>
      
      <sect3>
	<title>Dedicated</title>
	<indexterm><primary>OS/2</primary></indexterm>

	<para>If you will not be sharing the new drive with another operating
	  system, you may use the <literal>dedicated</literal> mode.  Remember
	  this mode can confuse Microsoft operating systems; however, no damage
	  will be done by them.  IBM's &os2; however, will
	  <quote>appropriate</quote> any partition it finds which it does not
	  understand.</para>
	
	<screen>&prompt.root; <userinput>dd if=/dev/zero of=/dev/da1 bs=1k count=1</userinput>
&prompt.root; <userinput>disklabel -Brw da1 auto</userinput>
&prompt.root; <userinput>disklabel -e da1</userinput>				# create the `e' partition
&prompt.root; <userinput>newfs -d0 /dev/da1e</userinput>
&prompt.root; <userinput>mkdir -p /1</userinput>
&prompt.root; <userinput>vi /etc/fstab</userinput>				# add an entry for /dev/da1e
&prompt.root; <userinput>mount /1</userinput></screen>
      
	<para>An alternate method is:</para>
      
	<screen>&prompt.root; <userinput>dd if=/dev/zero of=/dev/da1 count=2</userinput>
&prompt.root; <userinput>disklabel /dev/da1 | disklabel -BrR da1 /dev/stdin</userinput>
&prompt.root; <userinput>newfs /dev/da1e</userinput>
&prompt.root; <userinput>mkdir -p /1</userinput>
&prompt.root; <userinput>vi /etc/fstab</userinput>					# add an entry for /dev/da1e
&prompt.root; <userinput>mount /1</userinput></screen>

	<note><para>Since &os;&nbsp;5.1-RELEASE, the &man.bsdlabel.8;
	  utility replaces the old &man.disklabel.8; program.  With
	  &man.bsdlabel.8; a number of obsolete options and parameters
	  have been retired; in the examples above the option
	  <option>-r</option> should be removed with &man.bsdlabel.8;.
	  For more information, please refer to the &man.bsdlabel.8;
	  manual page.</para></note>
      </sect3>
    </sect2>
  </sect1>
  
  <sect1 id="raid">
    <title>RAID</title>

    <sect2 id="raid-soft">
      <title>Software RAID</title>

      <sect3 id="ccd">
	<sect3info>
	  <authorgroup>
	    <author>
	      <firstname>Christopher</firstname>
	      <surname>Shumway</surname>
	      <contrib>Original work by </contrib>
	    </author>
	  </authorgroup>
	  <authorgroup>
	    <author>
	      <firstname>Jim</firstname>
	      <surname>Brown</surname>
	      <contrib>Revised by </contrib>
	    </author>
	  </authorgroup>
	</sect3info>

<indexterm><primary>RAID</primary><secondary>software</secondary></indexterm>
<indexterm>
  <primary>RAID</primary><secondary>CCD</secondary>
</indexterm>

	<title>Concatenated Disk Driver (CCD) Configuration</title>
	<para>When choosing a mass storage solution the most important
	  factors to consider are speed, reliability, and cost.  It is 
	  rare to have all three in balance; normally a fast, reliable mass
	  storage device is expensive, and to cut back on cost either speed
	  or reliability must be sacrificed.</para>

          <para>In designing the system described below, cost was chosen
          as  the most important factor, followed by speed, then reliability.
          Data transfer speed for this system is ultimately
          constrained by the network.  And while reliability is very important,
          the CCD drive described below serves online data that is already
          fully backed up on CD-R's and can easily be replaced.</para>  

          <para>Defining your own requirements is the first step
          in choosing a mass storage solution.  If your requirements prefer
          speed or reliability over cost, your solution will differ from
          the system described in this section.</para>


	<sect4 id="ccd-installhw">
	  <title>Installing the Hardware</title>

	  <para>In addition to the IDE system disk, three Western 
            Digital 30GB, 5400 RPM IDE disks form the core
            of the CCD disk described below providing approximately
	    90GB of online storage.  Ideally,
	    each IDE disk would have its own IDE controller
	    and cable, but to minimize cost, additional 
	    IDE controllers were not used.  Instead the disks were
	    configured with jumpers so that each IDE controller has
            one master, and one slave.</para>

	  <para>Upon reboot, the system BIOS was configured to
	    automatically detect the disks attached.  More importantly,
	    FreeBSD detected them on reboot:</para>

	  <programlisting>ad0: 19574MB &lt;WDC WD205BA&gt; [39770/16/63] at ata0-master UDMA33
ad1: 29333MB &lt;WDC WD307AA&gt; [59598/16/63] at ata0-slave UDMA33
ad2: 29333MB &lt;WDC WD307AA&gt; [59598/16/63] at ata1-master UDMA33
ad3: 29333MB &lt;WDC WD307AA&gt; [59598/16/63] at ata1-slave UDMA33</programlisting>

 	  <note><para>If FreeBSD does not detect all the disks, ensure
 	    that you have jumpered them correctly.  Most IDE drives
 	    also have a <quote>Cable Select</quote> jumper.  This is
 	    <emphasis>not</emphasis> the jumper for the master/slave
 	    relationship.  Consult the drive documentation for help in
 	    identifying the correct jumper.</para></note>
 
 	  <para>Next, consider how to attach them as part of the file
 	    system.  You should research both &man.vinum.8; (<xref
 	    linkend="vinum-vinum">) and &man.ccd.4;.  In this
 	    particular configuration, &man.ccd.4; was chosen.</para>
	</sect4>

	<sect4 id="ccd-setup">
	  <title>Setting Up the CCD</title>

 	  <para>The driver &man.ccd.4; allows you to take
  	    several identical disks and concatenate them into one
  	    logical file system.  In order to use
 	    &man.ccd.4;, you need a kernel with
 	    &man.ccd.4; support built in.
 	    Add this line to your kernel configuration file, rebuild, and 
 	    reinstall the kernel:</para>

	  <programlisting>pseudo-device   ccd     4</programlisting>

	  <para>On 5.X systems, you have to use instead the following
	    line:</para>

	  <programlisting>device   ccd</programlisting>

	  <note><para>In FreeBSD&nbsp;5.X, it is not necessary to specify
	    a number of &man.ccd.4; devices, as the &man.ccd.4; device driver is now
	    self-cloning &mdash; new device instances will automatically be
	    created on demand.</para></note>

	  <para>The &man.ccd.4; support can also be
	    loaded as a kernel loadable module in FreeBSD 3.0 or
	    later.</para>

 	  <para>To set up &man.ccd.4;, you must first use
 	    &man.disklabel.8; to label the disks:</para>

	  <programlisting>disklabel -r -w ad1 auto
disklabel -r -w ad2 auto
disklabel -r -w ad3 auto</programlisting>

 	  <para>This creates a disklabel for <devicename>ad1c</devicename>, <devicename>ad2c</devicename> and <devicename>ad3c</devicename> that
  	    spans the entire disk.</para>

	  <note><para>Since &os;&nbsp;5.1-RELEASE, the &man.bsdlabel.8;
	    utility replaces the old &man.disklabel.8; program.  With
	    &man.bsdlabel.8; a number of obsolete options and parameters
	    have been retired; in the examples above the option
	    <option>-r</option> should be removed.  For more
	    information, please refer to the &man.bsdlabel.8;
	    manual page.</para></note>

 	  <para>The next step is to change the disk label type.  You
 	    can use &man.disklabel.8; to edit the
 	    disks:</para>

	  <programlisting>disklabel -e ad1
disklabel -e ad2
disklabel -e ad3</programlisting>

 	  <para>This opens up the current disk label on each disk with
 	    the editor specified by the <envar>EDITOR</envar>
 	    environment variable, typically &man.vi.1;.</para>

	  <para>An unmodified disk label will look something like
	    this:</para>

	  <programlisting>8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
  c: 60074784        0    unused        0     0     0   # (Cyl.    0 - 59597)</programlisting>

 	  <para>Add a new <literal>e</literal> partition for &man.ccd.4; to use. This
 	    can usually be copied from the <literal>c</literal> partition,
 	    but the <option>fstype</option> <emphasis>must</emphasis>
 	    be <userinput>4.2BSD</userinput>.  The disk label should
 	    now look something like this:</para>

	  <programlisting>8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
  c: 60074784        0    unused        0     0     0   # (Cyl.    0 - 59597)
  e: 60074784        0    4.2BSD        0     0     0   # (Cyl.    0 - 59597)</programlisting>

	</sect4>

	<sect4 id="ccd-buildingfs">
	  <title>Building the File System</title>

            <para>The device node for
	    <devicename>ccd0c</devicename> may not exist yet, so to
	    create it, perform the following commands:</para>

	  <programlisting>cd /dev
sh MAKEDEV ccd0</programlisting>

	  <note><para>In FreeBSD 5.0, &man.devfs.5; will automatically
	    manage device nodes in <filename>/dev</filename>, so use of
	    <command>MAKEDEV</command> is not necessary.</para></note>

	  <para>Now that you have all of the disks labeled, you must
	    build the &man.ccd.4;.  To do that,
	    use  &man.ccdconfig.8;, with options similar to the following:</para>

	    <programlisting>ccdconfig ccd0<co id="co-ccd-dev"> 32<co id="co-ccd-interleave"> 0<co id="co-ccd-flags"> /dev/ad1e<co id="co-ccd-devs"> /dev/ad2e /dev/ad3e</programlisting>

	  <para>The use and meaning of each option is shown below:</para>

          <calloutlist>
            <callout arearefs="co-ccd-dev">
	    <para>The first argument is the device to configure, in this case,
	    <devicename>/dev/ccd0c</devicename>. The <filename>/dev/</filename>
            portion is optional.</para>
            </callout>

            <callout arearefs="co-ccd-interleave">

	    <para>The interleave for the file system.  The interleave
	    defines the size of a stripe in disk blocks, each normally 512 bytes.
	    So, an interleave of 32 would be 16,384 bytes.</para>
            </callout>

            <callout arearefs="co-ccd-flags">
	    <para>Flags for &man.ccdconfig.8;.  If you want to enable drive
	    mirroring, you can specify a flag here. This 
	    configuration does not provide mirroring for  
	    &man.ccd.4;, so it is set at 0 (zero).</para>
            </callout>

            <callout arearefs="co-ccd-devs">
	    <para>The final arguments to &man.ccdconfig.8;
	    are the devices to place into the array.  Use the complete pathname 
	    for each device.</para>
            </callout>
          </calloutlist>


	  <para>After running &man.ccdconfig.8; the &man.ccd.4;
          is configured. A file system can be installed. Refer to &man.newfs.8; 
          for options, or simply run: </para>

	  <programlisting>newfs /dev/ccd0c</programlisting>


	</sect4>

	<sect4 id="ccd-auto">
	  <title>Making it All Automatic</title>

	  <para>Generally, you will want to mount the
	    &man.ccd.4; upon each reboot. To do this, you must
	    configure it first.  Write out your current configuration to
	    <filename>/etc/ccd.conf</filename> using the following command:</para>

	  <programlisting>ccdconfig -g &gt; /etc/ccd.conf</programlisting>

	  <para>During reboot, the script <command>/etc/rc</command>
	    runs <command>ccdconfig -C</command> if <filename>/etc/ccd.conf</filename>
	    exists. This automatically configures the
	    &man.ccd.4; so it can be mounted.</para>

	  <note><para>If you are booting into single user mode, before you can
	    &man.mount.8; the &man.ccd.4;, you
	    need to issue the following command to configure the
	    array:</para>

	  <programlisting>ccdconfig -C</programlisting>
          </note>

	  <para>To automatically mount the &man.ccd.4;,
            place an entry for the &man.ccd.4; in
	    <filename>/etc/fstab</filename> so it will be mounted at
	    boot time:</para>

	  <programlisting>/dev/ccd0c              /media       ufs     rw      2       2</programlisting>
	</sect4>
      </sect3>

      <sect3 id="vinum">
	<title>The Vinum Volume Manager</title>

<indexterm><primary>RAID</primary><secondary>software</secondary></indexterm>
<indexterm>
  <primary>RAID</primary>
  <secondary>Vinum</secondary>
</indexterm>

	<para>The Vinum Volume Manager is a block device driver which
	  implements virtual disk drives.  It isolates disk hardware
	  from the block device interface and maps data in ways which
	  result in an increase in flexibility, performance and
	  reliability compared to the traditional slice view of disk
	  storage.  &man.vinum.8; implements the RAID-0, RAID-1 and
	  RAID-5 models, both individually and in combination.</para>

	<para>See <xref linkend="vinum-vinum"> for more
	  information about &man.vinum.8;.</para>
      </sect3>
    </sect2>

    <sect2 id="raid-hard">
      <title>Hardware RAID</title>

      <indexterm>
	<primary>RAID</primary>
	<secondary>hardware</secondary>
      </indexterm>

      <para>FreeBSD also supports a variety of hardware <acronym>RAID</acronym>
        controllers.  These devices control a <acronym>RAID</acronym> subsystem
        without the need for FreeBSD specific software to manage the
        array.</para>

      <para>Using an on-card <acronym>BIOS</acronym>, the card controls most  of the disk operations
	itself.  The following is a brief setup description using a <acronym>Promise IDE RAID</acronym>
	controller.  When this card is installed and the system is started up, it 
	displays a prompt requesting information.  Follow the instructions
	to enter the card's setup screen.  From here, you have the ability to
	combine all the attached drives.  After doing so, the disk(s) will look like
	a single drive to FreeBSD.  Other <acronym>RAID</acronym> levels can be set up
	accordingly.
      </para>
    </sect2>
    
    <sect2>
      <title>Rebuilding ATA RAID1 Arrays</title>

      <para>FreeBSD allows you to hot-replace a failed disk in an array. This requires
	that you catch it before you reboot.</para>

      <para>You will probably see something like the following in <filename>/var/log/messages</filename> or in the &man.dmesg.8;
	output:</para>

      <programlisting>ad6 on monster1 suffered a hard error.
ad6: READ command timeout tag=0 serv=0 - resetting
ad6: trying fallback to PIO mode
ata3: resetting devices .. done
ad6: hard error reading fsbn 1116119 of 0-7 (ad6 bn 1116119; cn 1107 tn 4 sn 11) status=59 error=40
ar0: WARNING - mirror lost</programlisting>

      <para>Using &man.atacontrol.8;, check for further information:</para>

      <screen>&prompt.root; <userinput>atacontrol list</userinput>
ATA channel 0:
	Master:      no device present
	Slave:   acd0 &lt;HL-DT-ST CD-ROM GCR-8520B/1.00&gt; ATA/ATAPI rev 0

ATA channel 1:
	Master:      no device present
	Slave:       no device present

ATA channel 2:
	Master:  ad4 &lt;MAXTOR 6L080J4/A93.0500&gt; ATA/ATAPI rev 5
	Slave:       no device present

ATA channel 3:
	Master:  ad6 &lt;MAXTOR 6L080J4/A93.0500&gt; ATA/ATAPI rev 5
	Slave:       no device present

&prompt.root; <userinput>atacontrol status ar0</userinput>
ar0: ATA RAID1 subdisks: ad4 ad6 status: DEGRADED</screen>

      <procedure>
	<step>
	  <para>You will first need to detach the disk from the array so that you can
	    safely remove it:</para>

	  <screen>&prompt.root; <userinput>atacontrol detach 3</userinput></screen>
	</step>

	<step>
	  <para>Replace the disk.</para>
	</step>

	<step>
	  <para>Reattach the disk as a spare:</para>

	  <screen>&prompt.root; <userinput>atacontrol attach 3</userinput>
Master:  ad6 &lt;MAXTOR 6L080J4/A93.0500&gt; ATA/ATAPI rev 5
Slave:   no device present</screen>
	</step>

	<step>
	  <para>Rebuild the array:</para>

	  <screen>&prompt.root; <userinput>atacontrol rebuild ar0</userinput></screen>
	</step>

	<step>
	  <para>The rebuild command hangs until complete.  However, it is possible to open another
	  terminal (using <keycombo action="simul"><keycap>Alt</keycap> <keycap>F<replaceable>n</replaceable></keycap></keycombo>)
          and check on the progress by issuing the following command:</para>

	  <screen>&prompt.root; <userinput>dmesg | tail -10</userinput>
[output removed]
ad6: removed from configuration
ad6: deleted from ar0 disk1
ad6: inserted into ar0 disk1 as spare

&prompt.root; <userinput>atacontrol status ar0</userinput>
ar0: ATA RAID1 subdisks: ad4 ad6 status: REBUILDING 0% completed</screen>
	</step>

	<step>
	  <para>Wait until this operation completes.</para>
	</step>
      </procedure>
    </sect2>
  </sect1>
  
  <sect1 id="creating-cds">
    <sect1info>
      <authorgroup>
	<author>
	  <firstname>Mike</firstname>
	  <surname>Meyer</surname>
	  <contrib>Contributed by </contrib>
	  <!-- mwm@mired.org -->
	</author>
      </authorgroup>
      <!-- Apr 2001 -->
    </sect1info>

    <title>Creating and Using Optical Media (CDs)</title>
    <indexterm>
      <primary>CDROMs</primary>
      <secondary>creating</secondary>
    </indexterm>

    <sect2>
      <title>Introduction</title>

      <para>CDs have a number of features that differentiate them from
	conventional disks. Initially, they were not writable by the
	user. They are designed so that they can be read continuously without
	delays to move the head between tracks. They are also much easier
	to transport between systems than similarly sized media were at the
	time.</para>

      <para>CDs do have tracks, but this refers to a section of data to
	be read continuously and not a physical property of the disk. To
	produce a CD on FreeBSD, you prepare the data files that are going
	to make up the tracks on the CD, then write the tracks to the
	CD.</para>

      <indexterm><primary>ISO 9660</primary></indexterm>
      <indexterm>
        <primary>file systems</primary>
        <secondary>ISO 9660</secondary>
      </indexterm>
      <para>The ISO 9660 file system was designed to deal with these
	differences. It unfortunately codifies file system limits that were
	common then. Fortunately, it provides an extension mechanism that
	allows properly written CDs to exceed those limits while still
	working with systems that do not support those extensions.</para>

      <indexterm>
        <primary><filename role="package">sysutils/mkisofs</filename></primary>
      </indexterm>
      <para>The <filename role="package">sysutils/mkisofs</filename>
	program is used to produce a data file containing an ISO 9660 file
	system. It has options that support various extensions, and is
	described below. You can install it with the
	<filename role="package">sysutils/mkisofs</filename> port.</para>

      <indexterm>
        <primary>CD burner</primary>
        <secondary>ATAPI</secondary>
      </indexterm>
      <para>Which tool to use to burn the CD depends on whether your CD burner
	is ATAPI or something else. ATAPI CD burners use the <command><link
	linkend="burncd">burncd</link></command> program that is part of
	the base system. SCSI and USB CD burners should use
	<command><link linkend="cdrecord">cdrecord</link></command> from
	the <filename role="package">sysutils/cdrtools</filename> port.</para>

      <para><command>burncd</command> has a limited number of
	supported drives. To find out if a drive is supported, see the
	<ulink url="http://www.freebsd.dk/ata/">CD-R/RW supported
	  drives</ulink> list.</para>

      <note>
      <indexterm>
	<primary>CD burner</primary>
	<secondary>ATAPI/CAM driver</secondary>
      </indexterm>
	<para>If you run &os;&nbsp;5.X, &os;&nbsp;4.8-RELEASE version or
	  higher, it will be possible to use <command><link
	  linkend="cdrecord">cdrecord</link></command> and other tools
	  for SCSI drives on an ATAPI hardware with the <link
	  linkend="atapicam">ATAPI/CAM module</link>.</para>
      </note>
    </sect2>

    <sect2 id="mkisofs">
      <title>mkisofs</title>

      <para><filename role="package">sysutils/mkisofs</filename> produces an ISO 9660 file system
	that is an image of a directory tree in the &unix; file system name
	space. The simplest usage is:</para>

      <screen>&prompt.root; <userinput>mkisofs -o <replaceable>imagefile.iso</replaceable> <replaceable>/path/to/tree</replaceable></userinput></screen>

      <indexterm>
        <primary>file systems</primary>
        <secondary>ISO 9660</secondary>
      </indexterm>
      <para>This command will create an <replaceable>imagefile.iso</replaceable>
	containing an ISO 9660 file system that is a copy of the tree at
	<replaceable>/path/to/tree</replaceable>. In the process, it will
	map the file names to names that fit the limitations of the
	standard ISO 9660 file system, and will exclude files that have
	names uncharacteristic of ISO file systems.</para>
    
      <indexterm>
        <primary>file systems</primary>
        <secondary>HFS</secondary>
      </indexterm>
      <indexterm>
        <primary>file systems</primary>
        <secondary>Joliet</secondary>
      </indexterm>
      <para>A number of options are available to overcome those
	restrictions. In particular, <option>-R</option> enables the
	Rock Ridge extensions common to &unix; systems, <option>-J</option>
	enables Joliet extensions used by Microsoft systems, and
	<option>-hfs</option> can be used to create HFS file systems used
	by &macos;.</para>

      <para>For CDs that are going to be used only on FreeBSD systems,
	<option>-U</option> can be used to disable all filename
	restrictions. When used with <option>-R</option>, it produces a
	file system image that is identical to the FreeBSD tree you started
	from, though it may violate the ISO 9660 standard in a number of
	ways.</para>

      <indexterm>
        <primary>CDROMs</primary>
        <secondary>creating bootable</secondary>
      </indexterm>
      <para>The last option of general use is <option>-b</option>. This is
	used to specify the location of the boot image for use in producing an
	<quote>El Torito</quote> bootable CD. This option takes an
	argument which is the path to a boot image from the top of the
	tree being written to the CD. So, given that
	<filename>/tmp/myboot</filename> holds a bootable FreeBSD system
	with the boot image in
	<filename>/tmp/myboot/boot/cdboot</filename>, you could produce the
	image of an ISO 9660 file system in
	<filename>/tmp/bootable.iso</filename> like so:</para>

      <screen>&prompt.root; <userinput>mkisofs -U -R -b boot/cdboot -o /tmp/bootable.iso /tmp/myboot</userinput></screen>

      <para>Having done that, if you have <devicename>vn</devicename>
	(FreeBSD&nbsp;4.X), or <devicename>md</devicename>
	(FreeBSD&nbsp;5.X)
	configured in your kernel, you can mount the file system with:</para>

      <screen>&prompt.root; <userinput>vnconfig -e vn0c /tmp/bootable.iso</userinput>
&prompt.root; <userinput>mount -t cd9660 /dev/vn0c /mnt</userinput></screen>

      <para>for FreeBSD&nbsp;4.X, and for FreeBSD&nbsp;5.X:</para>

      <screen>&prompt.root; <userinput>mdconfig -a -t vnode -f /tmp/bootable.iso -u 0</userinput>
&prompt.root; <userinput>mount -t cd9660 /dev/md0 /mnt</userinput></screen>

      <para>At which point you can verify that <filename>/mnt</filename>
	and <filename>/tmp/myboot</filename> are identical.</para>

      <para>There are many other options you can use with
	<filename role="package">sysutils/mkisofs</filename> to fine-tune its behavior.  In particular:
	modifications to an ISO 9660 layout and the creation of Joliet
	and HFS discs.  See the	&man.mkisofs.8; manual page for details.</para>
    </sect2>

    <sect2 id="burncd">
      <title>burncd</title>
      <indexterm>
        <primary>CDROMs</primary>
        <secondary>burning</secondary>
      </indexterm>
      <para>If you have an ATAPI CD burner, you can use the
	<command>burncd</command> command to burn an ISO image onto a
	CD. <command>burncd</command> is part of the base system, installed
	as <filename>/usr/sbin/burncd</filename>.  Usage is very simple, as
	it has few options:</para>

      <screen>&prompt.root; <userinput>burncd -f <replaceable>cddevice</replaceable> data <replaceable>imagefile.iso</replaceable> fixate</userinput></screen>

      <para>Will burn a copy of <replaceable>imagefile.iso</replaceable> on
	<replaceable>cddevice</replaceable>. The default device is
	<filename>/dev/acd0</filename> (or <filename>/dev/acd0c</filename> under &os;&nbsp;4.X). See &man.burncd.8; for options to
	set the write speed, eject the CD after burning, and write audio
	data.</para>
    </sect2>

    <sect2 id="cdrecord">
      <title>cdrecord</title>

      <para>If you do not have an ATAPI CD burner, you will have to use
	<command>cdrecord</command> to burn your
	CDs. <command>cdrecord</command> is not part of the base system;
	you must install it from either the port at <filename role="package">sysutils/cdrtools</filename>
	or the appropriate
	package. Changes to the base system can cause binary versions of
	this program to fail, possibly resulting in a
	<quote>coaster</quote>. You should therefore either upgrade the
	port when you upgrade your system, or if you are <link
	linkend="stable">tracking -STABLE</link>, upgrade the port when a
	new version becomes available.</para>

      <para>While <command>cdrecord</command> has many options, basic usage
	is even simpler than <command>burncd</command>. Burning an ISO 9660
	image is done with:</para>

      <screen>&prompt.root; <userinput>cdrecord dev=<replaceable>device</replaceable> <replaceable>imagefile.iso</replaceable></userinput></screen>

      <para>The tricky part of using <command>cdrecord</command> is finding
	the <option>dev</option> to use. To find the proper setting, use
	the <option>-scanbus</option> flag of <command>cdrecord</command>,
	which might produce results like this:</para>
      <indexterm>
        <primary>CDROMs</primary>
        <secondary>burning</secondary>
      </indexterm>
      <screen>&prompt.root; <userinput>cdrecord -scanbus</userinput>
Cdrecord 1.9 (i386-unknown-freebsd4.2) Copyright (C) 1995-2000 J&ouml;rg Schilling
Using libscg version 'schily-0.1'
scsibus0:
        0,0,0     0) 'SEAGATE ' 'ST39236LW       ' '0004' Disk
        0,1,0     1) 'SEAGATE ' 'ST39173W        ' '5958' Disk
        0,2,0     2) *
        0,3,0     3) 'iomega  ' 'jaz 1GB         ' 'J.86' Removable Disk
        0,4,0     4) 'NEC     ' 'CD-ROM DRIVE:466' '1.26' Removable CD-ROM
        0,5,0     5) *
        0,6,0     6) *
        0,7,0     7) *
scsibus1:
        1,0,0   100) *
        1,1,0   101) *
        1,2,0   102) *
        1,3,0   103) *
        1,4,0   104) *
        1,5,0   105) 'YAMAHA  ' 'CRW4260         ' '1.0q' Removable CD-ROM
        1,6,0   106) 'ARTEC   ' 'AM12S           ' '1.06' Scanner
        1,7,0   107) *</screen>

      <para>This lists the appropriate <option>dev</option> value for the
	devices on the list. Locate your CD burner, and use the three
	numbers separated by commas as the value for
	<option>dev</option>. In this case, the CRW device is 1,5,0, so the
	appropriate input would be
	<option>dev=1,5,0</option>. There are easier
	ways to specify this value; see &man.cdrecord.1; for
	details. That is also the place to look for information on writing
	audio tracks, controlling the speed, and other things.</para>
    </sect2>

    <sect2 id="duplicating-audiocds">
      <title>Duplicating Audio CDs</title>

      <para>You can duplicate an audio CD by extracting the audio data from
	the CD to a series of files, and then writing these files to a blank
	CD.  The process is slightly different for ATAPI and SCSI
	drives.</para>

      <procedure>
	<title>SCSI Drives</title>

	<step>
	  <para>Use <command>cdda2wav</command> to extract the audio.</para>

	  <screen>&prompt.user; <userinput>cdda2wav -v255 -D2,0 -B -Owav</userinput></screen>
	</step>

	<step>
	  <para>Use <command>cdrecord</command> to write the
	    <filename>.wav</filename> files.</para>

	  <screen>&prompt.user; <userinput>cdrecord -v dev=<replaceable>2,0</replaceable> -dao -useinfo  *.wav</userinput></screen>

	  <para>Make sure that <replaceable>2.0</replaceable> is set
	    appropriately, as described in <xref linkend="cdrecord">.</para>
	</step>
      </procedure>

      <procedure>
	<title>ATAPI Drives</title>

	<step>
	  <para>The ATAPI CD driver makes each track available as
	    <filename>/dev/acd<replaceable>d</replaceable>t<replaceable>nn</replaceable></filename>,
	    where <replaceable>d</replaceable> is the drive number, and
	    <replaceable>nn</replaceable> is the track number written with two
	    decimal digits, prefixed with zero as needed.
	    So the first track on the first disk is
	    <filename>/dev/acd0t01</filename>, the second is
	    <filename>/dev/acd0t02</filename>, the third is
	    <filename>/dev/acd0t03</filename>, and so on.</para>

	  <para>Make sure the appropriate files exist in
	    <filename>/dev</filename>.</para>

	  <screen>&prompt.root; <userinput>cd /dev</userinput>
&prompt.root; <userinput>sh MAKEDEV acd0t99</userinput></screen>

	  <note><para>In FreeBSD 5.0, &man.devfs.5; will automatically
	    create and manage entries in <filename>/dev</filename>
	    for you, so it is not necessary to use
	    <command>MAKEDEV</command>.</para></note>
	</step>

	<step>
	  <para>Extract each track using &man.dd.1;.  You must also use a
	    specific block size when extracting the files.</para>

	  <screen>&prompt.root; <userinput>dd if=/dev/acd0t01 of=track1.cdr bs=2352</userinput>
&prompt.root; <userinput>dd if=/dev/acd0t02 of=track2.cdr bs=2352</userinput>
...
</screen>
	</step>

	<step>
	  <para>Burn the extracted files to disk using
	    <command>burncd</command>.  You must specify that these are audio
	    files, and that <command>burncd</command> should fixate the disk
	    when finished.</para>

	  <screen>&prompt.root; <userinput>burncd -f <replaceable>/dev/acd0</replaceable> audio track1.cdr track2.cdr <replaceable>...</replaceable> fixate</userinput></screen>
	</step>
      </procedure>
    </sect2>

    <sect2 id="imaging-cd">
      <title>Duplicating Data CDs</title>

      <para>You can copy a data CD to a image file that is
	functionally equivalent to the image file created with
	<filename role="package">sysutils/mkisofs</filename>, and you can use it to duplicate
	any data CD.  The example given here assumes that your CDROM
	device is <devicename>acd0</devicename>.  Substitute your
	correct CDROM device.  Under &os;&nbsp;4.X, a <literal>c</literal> must be appended
	to the end of the device name to indicate the entire partition
	or, in the case of CDROMs, the entire disc.</para>

      <screen>&prompt.root; <userinput>dd if=/dev/acd0 of=file.iso bs=2048</userinput></screen>

      <para>Now that you have an image, you can burn it to CD as
	described above.</para>
    </sect2>

    <sect2 id="mounting-cd">
      <title>Using Data CDs</title>

      <para>Now that you have created a standard data CDROM, you
	probably want to mount it and read the data on it.  By
	default, &man.mount.8; assumes that a file system is of type
	<literal>ufs</literal>.  If you try something like:</para>

      <screen>&prompt.root; <userinput>mount /dev/cd0 /mnt</userinput></screen>

      <para>you will get a complaint about <errorname>Incorrect super
	  block</errorname>, and no mount. The CDROM is not a
	  <literal>UFS</literal> file system, so attempts to mount it
	  as such will fail.  You just need to tell &man.mount.8; that
	  the file system is of type <literal>ISO9660</literal>, and
	  everything will work.  You do this by specifying the
	  <option>-t cd9660</option> option &man.mount.8;. For
	  example, if you want to mount the CDROM device,
	  <devicename>/dev/cd0</devicename>, under
	  <filename>/mnt</filename>, you would execute:</para>

          <screen>&prompt.root; <userinput>mount -t cd9660 /dev/cd0 /mnt</userinput></screen>

      <para>Note that your device name
	(<devicename>/dev/cd0</devicename> in this example) could be
	different, depending on the interface your CDROM uses. Also,
	the <option>-t cd9660</option> option just executes
	&man.mount.cd9660.8;. The above example could be shortened
	to:</para>

<screen>&prompt.root; <userinput>mount_cd9660 /dev/cd0 /mnt</userinput></screen>

      <para>You can generally use data CDROMs from any vendor in this
	way.  Disks with certain ISO 9660 extensions might behave
	oddly, however.  For example, Joliet disks store all filenames
	in two-byte Unicode characters.  The FreeBSD kernel does not
	speak Unicode (yet!), so non-English characters show up as
	question marks.  (If you are running FreeBSD 4.3 or later, the
	CD9660 driver includes hooks to load an appropriate Unicode
	conversion table on the fly.  Modules for some of the common
	encodings are available via the
	<filename role="package">sysutils/cd9660_unicode</filename> port.)</para>

      <para>Occasionally, you might get <errorname>Device not
	configured</errorname> when trying to mount a CDROM.  This
	usually means that the CDROM drive thinks that there is no
	disk in the tray, or that the drive is not visible on the bus.
	It can take a couple of seconds for a CDROM drive to realize
	that it has been fed, so be patient.</para>

      <para>Sometimes, a SCSI CDROM may be missed because it did not
	have enough time to answer the bus reset.  If you have a SCSI
	CDROM please add the following option to your kernel
	configuration and <link linkend="kernelconfig-building">rebuild your kernel</link>.</para>

      <programlisting>options SCSI_DELAY=15000</programlisting>

      <para>This tells your SCSI bus to pause 15 seconds during boot,
	to give your CDROM drive every possible chance to answer the
	bus reset.</para>
    </sect2>

    <sect2 id="rawdata-cd">
      <title>Burning Raw Data CDs</title>

      <para>You can choose to burn a file directly to CD, without
	creating an ISO 9660 file system.  Some people do this for
	backup purposes.  This runs more quickly than burning a
	standard CD:</para>

      <screen>&prompt.root; <userinput>burncd -f /dev/acd1 -s 12 data archive.tar.gz fixate</userinput></screen>

      <para>In order to retrieve the data burned to such a CD, you
	  must read data from the raw device node:</para>

      <screen>&prompt.root; <userinput>tar xzvf /dev/acd1</userinput></screen>

      <para>You cannot mount this disk as you would a normal CDROM.
	  Such a CDROM cannot be read under any operating system
	  except FreeBSD.  If you want to be able to mount the CD, or
	  share data with another operating system, you must use
	  <filename role="package">sysutils/mkisofs</filename> as described above.</para>
    </sect2>

    <sect2 id="atapicam">
      <sect2info>
	<authorgroup>
	  <author>
	    <firstname>Marc</firstname>
	    <surname>Fonvieille</surname>
	    <contrib>Contributed by </contrib>
	  </author>
	</authorgroup>
      </sect2info>

      <indexterm>
	<primary>CD burner</primary>
	<secondary>ATAPI/CAM driver</secondary>
      </indexterm>
      <title>Using the ATAPI/CAM Driver</title>

      <para>This driver allows ATAPI devices (CD-ROM, CD-RW, DVD
	drives etc...) to be accessed through the SCSI subsystem, and
	so allows the use of applications like <filename
	role="package">sysutils/cdrdao</filename> or
	&man.cdrecord.1;.</para>

      <para>To use this driver, you will need to add the following
	lines to your kernel configuration file:</para>

      <programlisting>device atapicam
device scbus
device cd
device pass</programlisting>

      <para>You also need the following lines in your kernel
	configuration file:</para>

      <programlisting>device ata
device atapicd</programlisting>

      <para>Both of which should already be present.</para>

      <para>Then rebuild, install your new kernel, and reboot your
	machine.  During the boot process, your burner should show up,
	like so:</para>

      <screen>acd0: CD-RW &lt;MATSHITA CD-RW/DVD-ROM UJDA740&gt; at ata1-master PIO4
cd0 at ata1 bus 0 target 0 lun 0
cd0: &lt;MATSHITA CDRW/DVD UJDA740 1.00&gt; Removable CD-ROM SCSI-0 device
cd0: 16.000MB/s transfers
cd0: Attempt to query device size failed: NOT READY, Medium not present - tray closed</screen>

      <para>The drive could now be accessed via the
	<filename>/dev/cd0</filename> device name, for example to
	mount a CD-ROM on <filename>/mnt</filename>, just type the
	following:</para>

      <screen>&prompt.root; <userinput>mount -t cd9660 <replaceable>/dev/cd0</replaceable> /mnt</userinput></screen>

      <para>As <username>root</username>, you can run the following
	command to get the SCSI address of the burner:</para>

      <screen>&prompt.root; <userinput>camcontrol devlist</userinput>
&lt;MATSHITA CDRW/DVD UJDA740 1.00&gt;   at scbus1 target 0 lun 0 (pass0,cd0)</screen>

      <para>So <literal>1,0,0</literal> will be the SCSI address to
	use with &man.cdrecord.1; and other SCSI application.</para>

      <para>For more information about ATAPI/CAM and SCSI system,
	refer to the &man.atapicam.4; and &man.cam.4; manual
	pages.</para>
    </sect2>
  </sect1>

  <sect1 id="creating-dvds">
    <sect1info>
      <authorgroup>
	<author>
	  <firstname>Marc</firstname>
	  <surname>Fonvieille</surname>
	  <contrib>Contributed by </contrib>
	</author>
      </authorgroup>
      <!-- Feb 2004 -->
    </sect1info>

    <title>Creating and Using Optical Media (DVDs)</title>
    <indexterm>
      <primary>DVD</primary>
      <secondary>burning</secondary>
    </indexterm>

    <sect2>
      <title>Introduction</title>

      <para>Compared to the CD, the DVD is the next generation of
	optical media storage technology.  The DVD can hold more data
	than any CD and is nowadays the standard for video
	publishing.</para>

      <para>Five physical recordable formats can be defined for what
	we will call a recordable DVD:</para>

      <itemizedlist>
	<listitem>
	  <para>DVD-R: This was the first DVD recordable format
	    available.  The DVD-R standard is defined by the <ulink
	    url="http://www.dvdforum.com/forum.shtml">DVD Forum</ulink>.
	    This format is write once.</para>
	</listitem>

	<listitem>
	  <para>DVD-RW: This is the rewriteable version of
	    the DVD-R standard.  A DVD-RW can be rewritten about 1000
	    times.</para>
	</listitem>

	<listitem>
	  <para>DVD-RAM: This is also a rewriteable format
	    supported by the DVD Forum.  A DVD-RAM can be seen as a
	    removable hard drive.  However, this media is not
	    compatible with most DVD-ROM drives and DVD-Video players;
	    only few DVD writers will support the DVD-RAM.</para>
	</listitem>

	<listitem>
	  <para>DVD+RW: This is a rewriteable format defined by
	    the <ulink url="http://www.dvdrw.com/">DVD+RW
	    Alliance</ulink>.  A DVD+RW can be rewritten about 1000
	    times.</para>
	</listitem>

	<listitem>
	  <para>DVD+R: This format is the write once variation
	    of the DVD+RW format.</para>
	</listitem>
      </itemizedlist>

      <para>A single layer recordable DVD can hold up to
	4,700,000,000&nbsp;bytes which is actually 4.38&nbsp;GB or
	4485&nbsp;MB (1 kilobyte is 1024 bytes).</para>

      <note>
	<para>A difference must be done between the physical media and
	  the application.   For example a DVD-Video is a specific
	  file system that can be written on any recordable DVD
	  physical media: DVD-R, DVD+R, DVD-RW etc.  Before choosing
	  the type of media, you just must be sure the burner and the
	  DVD-Video player (a standalone player or a DVD-ROM drive on
	  a computer) are compatible with the media.</para></note>
    </sect2>

    <sect2>
      <title>Configuration</title>

      <para>The program &man.growisofs.1; will be used to perform DVD
	recording.  This command is part of the
	<application>dvd+rw-tools</application> utilities (<filename
	role="package">sysutils/dvd+rw-tools</filename>).  The
	<application>dvd+rw-tools</application> support all DVD media
	types.</para>

      <para>These tools use the SCSI subsystem to access to the
	devices, therefore the <link linkend="atapicam">ATAPI/CAM
	support</link> must be added to your kernel.</para>

      <para>Before attempting to use the
	<application>dvd+rw-tools</application> you should consult the
	<ulink
	url="http://fy.chalmers.se/~appro/linux/DVD+RW/hcn.html">dvd+rw-tools'
	hardware compatibility notes</ulink> for any information
	related to your DVD burner.</para>
    </sect2>

    <sect2>
      <title>Burning Data DVDs</title>

      <para>The &man.growisofs.1; command is a frontend to <link
	linkend="mkisofs">mkisofs</link>, it will invoke
	&man.mkisofs.8; to create the file system layout and will
	perform the write on the DVD.  This means you do not need to
	create an image of the data before the burning process.</para>
	
      <para>To burn onto a DVD+R or a DVD-R the data from the <filename
	role="directory">/path/to/data</filename> directory, use the
	following command:</para>

      <screen>&prompt.root; <userinput>growisofs -dvd-compat -Z <replaceable>/dev/cd0</replaceable> -J -R <replaceable>/path/to/data</replaceable></userinput></screen>

      <para>The options <option>-J -R</option> are passed to
	&man.mkisofs.8; for the file system creation (in this case: an
	ISO 9660 file system with Joliet and Rock Ridge extensions),
	consult the &man.mkisofs.8; manual page for more
	details.</para>

      <para>The option <option>-Z</option> is used for the initial
	session recording in any case: multiple sessions or not.  The
	DVD device, <replaceable>/dev/cd0</replaceable>, must be
	changed according to your configuration.  The
	<option>-dvd-compat</option> parameter will close the disk,
	the recording will be unappendable.  This should provide more
	media compatibility with DVD-ROM drives.</para>

      <para>It is also possible to burn a pre-mastered image, for
	example to burn the image
	<replaceable>imagefile.iso</replaceable>, we will run:</para>

      <screen>&prompt.root; <userinput>growisofs -dvd-compat -Z <replaceable>/dev/cd0</replaceable>=<replaceable>imagefile.iso</replaceable></userinput></screen>

      <para>The write speed should be detected and automatically set
	according to the media and the drive being used.  If you want
	to force the write speed, use the <option>-speed=</option>
	parameter.  For more information, read the &man.growisofs.1;
	manual page.</para>
    </sect2>

    <indexterm>
      <primary>DVD</primary>
      <secondary>DVD-Video</secondary>
    </indexterm>

    <sect2>
      <title>Burning a DVD-Video</title>

      <para>A DVD-Video is a specific file system based on ISO 9660
	and the micro-UDF (M-UDF) specifications.  The DVD-Video also
	presents a specific file structure hierarchy, it is the reason
	why you need a particular program such as <filename
	role="package">sysutils/dvdauthor</filename> to author the
	DVD.</para>

      <para>If you already have an image of the DVD-Video file system,
	just burn it in the same way as for any image, see the
	previous section for an example.  If you have made the DVD
	authoring and the result is in, for example, the directory
	<filename role="directory">/path/to/video</filename>, the
	following command should be used to burn the DVD-Video:</para>

      <screen>&prompt.root; <userinput>growisofs -Z <replaceable>/dev/cd0</replaceable> -dvd-video <replaceable>/path/to/video</replaceable></userinput></screen>

      <para>The <option>-dvd-video</option> option will tell
	&man.mkisofs.8; to create a DVD-Video file system
	layout.</para>
    </sect2>

    <indexterm>
      <primary>DVD</primary>
      <secondary>DVD+RW</secondary>
    </indexterm>

    <sect2>
      <title>Using a DVD+RW</title>

      <para>Unlike CD-RW, a virgin DVD+RW needs to be formatted before
	first use.  To format the DVD+RW, use the following:</para>

      <screen>&prompt.root; <userinput>dvd+rw-format <replaceable>/dev/cd0</replaceable></userinput></screen>

      <para>You need to perform this operation just once, keep in mind
	that only virgin DVD+RW medias need to be formatted.  Then you
	can burn the DVD+RW in the way seen in previous
	sections.</para>

      <para>If you want to burn new data (burn a totally new file
	system not append some data) onto a DVD+RW, you do not need to
	blank it, you just have to write over the previous recording
	(in performing a new initial session), like this:</para>

      <screen>&prompt.root; <userinput>growisofs -Z <replaceable>/dev/cd0</replaceable> -J -R <replaceable>/path/to/newdata</replaceable></userinput></screen>

      <para>DVD+RW format offers the possibility to easily append data
	to a previous recording.  The operation consists in merging a
	new session to the existing one, it is not multisession
	writing, &man.growisofs.1; will <emphasis>grow</emphasis> the
	ISO 9660 file system present on the media.</para>

      <para>For example, if we want to append data to our previous
	DVD+RW, we have to use the following:</para>

      <screen>&prompt.root; <userinput>growisofs -M <replaceable>/dev/cd0</replaceable> -J -R <replaceable>/path/to/nextdata</replaceable></userinput></screen>

      <para>The same &man.mkisofs.8; options we used to burn the
	initial session should be used during next writes.</para>

      <note>
	<para>You must not use the <option>-dvd-compat</option> option
	  during the initial session if you want to be able to append
	  any data, or you will have to rewrite a new initial
	  session.</para>
      </note>

      <para>If for any reason you really want to blank the media, do
	the following:</para>

      <screen>&prompt.root; <userinput>growisofs -Z <replaceable>/dev/cd0</replaceable>=<replaceable>/dev/zero</replaceable></userinput></screen>
    </sect2>

    <indexterm>
      <primary>DVD</primary>
      <secondary>DVD-RW</secondary>
    </indexterm>

    <sect2>
      <title>Using a DVD-RW</title>

      <para>A DVD-RW accepts two disc formats: the incremental
	sequential one and the restricted overwrite.  By default
	DVD-RW discs are in sequential format.</para>

      <para>A virgin DVD-RW can be directly written without the need
	of a formatting operation, however a non-virgin DVD-RW in
	sequential format needs to be blanked before to be able to
	write a new initial session.</para>

      <para>To blank a DVD-RW in sequential mode, run:</para>

      <screen>&prompt.root; <userinput>dvd+rw-format -blank=full <replaceable>/dev/cd0</replaceable></userinput></screen>

      <note>
	<para>A full blanking (<option>-blank=full</option>) will take
	  about one hour on a 1x media.  A fast blanking can be
	  performed using the <option>-blank</option> option if the
	  DVD-RW will be recorded in Disk-At-Once (DAO) mode.  To burn
	  the DVD-RW in DAO mode, use the command:</para>

	<screen>&prompt.root; <userinput>growisofs -use-the-force-luke=dao -Z <replaceable>/dev/cd0</replaceable>=<replaceable>imagefile.iso</replaceable></userinput></screen>

	<para>The <option>-use-the-force-luke=dao</option> option
	  should not be required since &man.growisofs.1; attempts to
	  detect minimally (fast blanked) media and engage DAO
	  write.</para>

	<para>In fact one should use restricted overwrite mode with
	  any DVD-RW, this format is more flexible than the default
	  incremental sequential one.</para>
      </note>

      <para>To write data on a sequential DVD-RW, use the same
	instructions as for the other DVD formats:</para>

      <screen>&prompt.root; <userinput>growisofs -Z <replaceable>/dev/cd0</replaceable> -J -R <replaceable>/path/to/data</replaceable></userinput></screen>

      <para>If you want to append some data to your previous
	recording, you will have to use the &man.growisofs.1;
	<option>-M</option> option.  However, if you perform data
	addition on a DVD-RW in incremental sequential mode, a new
	session will be created on the disc and the result will be a
	multi-session disc.</para>

      <para>A DVD-RW in restricted overwrite format does not need to
	be blanked before a new initial session, you just have to
	overwrite the disc with the <option>-Z</option> option, this
	is similar to the DVD+RW case.  It is also possible to grow an
	existing ISO 9660 file system written on the disc in a same
	way as for a DVD+RW with the <option>-M</option> option.  The
	result will be a one-session DVD.</para>

      <para>To put a DVD-RW in the restricted overwrite format, the
	following command must be used:</para>

      <screen>&prompt.root; <userinput>dvd+rw-format <replaceable>/dev/cd0</replaceable></userinput></screen>

      <para>To change back to the sequential format use:</para>

      <screen>&prompt.root; <userinput>dvd+rw-format -blank=full <replaceable>/dev/cd0</replaceable></userinput></screen>
    </sect2>

    <sect2>
      <title>Multisession</title>

      <para>Very few DVD-ROM and DVD-Video players support
	multisession DVDs, they will most of time, hopefully, only read
	the first session.  DVD+R, DVD-R and DVD-RW in sequential
	format can accept multiple sessions, the notion of multiple
	sessions does not exist for the DVD+RW and the DVD-RW
	restricted overwrite formats.</para>

      <para>Using the following command after an initial (non-closed)
	session on a DVD+R, DVD-R, or DVD-RW in sequential format,
	will add a new session to the disc:</para>

      <screen>&prompt.root; <userinput>growisofs -M <replaceable>/dev/cd0</replaceable> -J -R <replaceable>/path/to/nextdata</replaceable></userinput></screen>
    </sect2>

    <sect2>
      <title>For More Information</title>

      <para>To obtain more information about a DVD, the
	<command>dvd+rw-mediainfo
	<replaceable>/dev/cd0</replaceable></command> command can be
	ran with the disc in the drive.</para>

      <para>More information about the
	<application>dvd+rw-tools</application> can be found in
	the &man.growisofs.1; manual page, on the <ulink
	url="http://fy.chalmers.se/~appro/linux/DVD+RW/">dvd+rw-tools
	web site</ulink> and in the <ulink
	url="http://lists.debian.org/cdwrite/">cdwrite mailing
	list</ulink> archives.</para>
    </sect2>
  </sect1>

  <sect1 id="floppies">
    <sect1info>
      <authorgroup>
	<author>
	  <firstname>Julio</firstname>
	  <surname>Merino</surname>
	  <contrib>Original work by </contrib>
	</author>
      </authorgroup>
      <!-- 24 Dec 2001 -->
      <authorgroup>
	<author>
	  <firstname>Martin</firstname>
	  <surname>Karlsson</surname>
	  <contrib>Rewritten by </contrib>
	</author>
      </authorgroup>
      <!-- 27 Apr 2003 -->
    </sect1info>

    <title>Creating and Using Floppy Disks</title>

    <para>Storing data on floppy disks is sometimes useful, for
      example when one does not have any other removable storage media
      or when one needs to transfer small amounts of data to another
      computer.</para>

    <para>This section will explain how to use floppy disks in
      FreeBSD.  It will primarily cover formatting and usage of
      3.5inch DOS floppies, but the concepts are similar for other
      floppy disk formats.</para>

    <sect2>
      <title>Formatting Floppies</title>

      <sect3>
	<title>The Device</title>

	<para>Floppy disks are accessed through entries in
	  <filename>/dev</filename>, just like other devices.  To
	  access the raw floppy disk in 4.X and earlier releases, one
	  uses
	  <filename>/dev/fd<replaceable>N</replaceable></filename>,
	  where <replaceable>N</replaceable> stands for the drive
	  number, usually 0, or
	  <filename>/dev/fd<replaceable>NX</replaceable></filename>,
	  where <replaceable>X</replaceable> stands for a
	  letter.</para>

	<para>In 5.0 or newer releases, simply use
	  <filename>/dev/fd<replaceable>N</replaceable></filename>.</para>

	<sect4>
	  <title>The Disk Size in 4.X and Earlier Releases</title>

	  <para>There are also <filename>/dev/fd<replaceable>N</replaceable>.<replaceable>size</replaceable></filename>
	    devices, where <replaceable>size</replaceable> is a floppy disk
	    size in kilobytes.  These entries are used at low-level format
	    time to determine the disk size.  1440kB is the size that will be 
	    used in the following examples.</para>

	  <para>Sometimes the entries under <filename>/dev</filename> will
	    have to be (re)created.  To do that, issue:</para>

	  <screen>&prompt.root; <userinput>cd /dev && ./MAKEDEV "fd*"</userinput></screen>
	</sect4>

	<sect4>
	  <title>The Disk Size in 5.0 and Newer Releases</title>

	  <para>In 5.0, &man.devfs.5; will automatically
	    manage device nodes in <filename>/dev</filename>, so use of
	    <command>MAKEDEV</command> is not necessary.</para>
	  
	  <para>The desired disk size is passed to &man.fdformat.1; through
	    the <option>-f</option> flag.  Supported sizes are listed in
	  &man.fdcontrol.8;, but be advised that 1440kB is what works best.</para>
	</sect4>
      </sect3>

      <sect3>
	<title>Formatting</title>

	<para>A floppy disk needs to be low-level formated before it
	  can be used.  This is usually done by the vendor, but
	  formatting is a good way to check media integrity.  Although
	  it is possible to force larger (or smaller) disk sizes,
	  1440kB is what most floppy disks are designed for.</para>

	<para>To low-level format the floppy disk you need to use
	  &man.fdformat.1;.  This utility expects the device name as an
	  argument.</para>

	  <para>Make note of any error messages, as these can help
	    determine if the disk is good or bad.</para>

	<sect4>
	  <title>Formatting in 4.X and Earlier Releases</title>

	  <para>Use the
	    <filename>/dev/fd<replaceable>N</replaceable>.<replaceable>size</replaceable></filename>
	    devices to format the floppy.  Insert a new 3.5inch floppy
	    disk in your drive and issue:</para>

	  <screen>&prompt.root; <userinput>/usr/sbin/fdformat /dev/fd0.1440</userinput></screen>

	</sect4>

	<sect4>
	  <title>Formatting in 5.0 and Newer Releases</title>

	  <para>Use the
	    <filename>/dev/fd<replaceable>N</replaceable></filename>
	    devices to format the floppy.  Insert a new 3.5inch floppy
	    disk in your drive and issue:</para>

	  <screen>&prompt.root; <userinput>/usr/sbin/fdformat -f 1440 /dev/fd0</userinput></screen>

	</sect4>
      </sect3>
    </sect2>



    <sect2>
      <title>The Disk Label</title>

      <para>After low-level formatting the disk, you will need to
	place a disk label on it.  This disk label will be destroyed
	later, but it is needed by the system to determine the size of
	the disk and its geometry later.</para>

      <para>The new disk label will take over the whole disk, and will
	contain all the proper information about the geometry of the
	floppy.  The geometry values for the disk label are listed in
	<filename>/etc/disktab</filename>.</para>

      <para>You can run now &man.disklabel.8; like so:</para>

      <screen>&prompt.root; <userinput>/sbin/disklabel -B -r -w /dev/fd0 fd1440</userinput></screen>

      <note><para>Since &os;&nbsp;5.1-RELEASE, the &man.bsdlabel.8;
	utility replaces the old &man.disklabel.8; program.  With
	&man.bsdlabel.8; a number of obsolete options and parameters
	have been retired; in the example above the option
	<option>-r</option> should be removed.  For more
	information, please refer to the &man.bsdlabel.8;
	manual page.</para></note>

    </sect2>

    <sect2>
      <title>The File System</title>

      <para>Now the floppy is ready to be high-level formated. This
	will place a new file system on it, which will let FreeBSD read
	and write to the disk.  After creating the new file system, the
	disk label is destroyed, so if you want to reformat the disk, you
	will have to recreate the disk label.</para>

      <para>The floppy's file system can be either UFS or FAT.
	 FAT is generally a better choice for floppies.</para>

      <para>To put a new file system on the floppy, issue:</para>

      <screen>&prompt.root; <userinput>/sbin/newfs_msdos /dev/fd0</userinput></screen>

      <para>The disk is now ready for use.</para>
    </sect2>


    <sect2>
      <title>Using the Floppy</title>

      <para>To use the floppy, mount it with &man.mount.msdos.8; (in
	4.X and earlier releases) or &man.mount.msdosfs.8; (in 5.0 or
	newer releases).  One can also use
	<filename role="package">emulators/mtools</filename> from the ports
	collection.</para>
    </sect2>
  </sect1>
  
  <sect1 id="backups-tapebackups">
    <title>Creating and Using Data Tapes</title>

    <indexterm><primary>tape media</primary></indexterm>
    <para>The major tape media are the 4mm, 8mm, QIC, mini-cartridge and
      DLT.</para>

    <sect2 id="backups-tapebackups-4mm">
      <title>4mm (DDS: Digital Data Storage)</title>

      <indexterm>
        <primary>tape media</primary>
	<secondary>DDS (4mm) tapes</secondary>
      </indexterm>
      <indexterm>
        <primary>tape media</primary>
	<secondary>QIC tapes</secondary>
      </indexterm>
      <para>4mm tapes are replacing QIC as the workstation backup media of
	choice.  This trend accelerated greatly when Conner purchased Archive,
	a leading manufacturer of QIC drives, and then stopped production of
	QIC drives.  4mm drives are small and quiet but do not have the
	reputation for reliability that is enjoyed by 8mm drives.  The
	cartridges are less expensive and smaller (3 x 2 x 0.5 inches, 76 x 51
	x 12 mm) than 8mm cartridges.  4mm, like 8mm, has comparatively short
	head life for the same reason, both use helical scan.</para>

      <para>Data throughput on these drives starts ~150&nbsp;kB/s, peaking at ~500&nbsp;kB/s.
	Data capacity starts at 1.3&nbsp;GB and ends at 2.0&nbsp;GB.  Hardware
	compression, available with most of these drives, approximately
	doubles the capacity.  Multi-drive tape library units can have 6
	drives in a single cabinet with automatic tape changing.  Library
	capacities reach 240&nbsp;GB.</para>

      <para>The DDS-3 standard now supports tape capacities up to 12&nbsp;GB (or
	24&nbsp;GB compressed).</para>

      <para>4mm drives, like 8mm drives, use helical-scan.  All the benefits
	and drawbacks of helical-scan apply to both 4mm and 8mm drives.</para>

      <para>Tapes should be retired from use after 2,000 passes or 100 full
	backups.</para>
    </sect2>

    <sect2 id="backups-tapebackups-8mm">
      <title>8mm (Exabyte)</title>
      <indexterm>
        <primary>tape media</primary>
	<secondary>Exabyte (8mm) tapes</secondary>
      </indexterm>

      <para>8mm tapes are the most common SCSI tape drives; they are the best
	choice of exchanging tapes.  Nearly every site has an Exabyte 2&nbsp;GB 8mm
	tape drive.  8mm drives are reliable, convenient and quiet. Cartridges
	are inexpensive and small (4.8 x 3.3 x 0.6 inches; 122 x 84 x 15 mm).
	One downside of 8mm tape is relatively short head and tape life due to
	the high rate of relative motion of the tape across the heads.</para>

      <para>Data throughput ranges from ~250&nbsp;kB/s to ~500&nbsp;kB/s.  Data sizes start
	at 300&nbsp;MB and go up to 7&nbsp;GB.  Hardware compression, available with
	most of these drives, approximately doubles the capacity.  These
	drives are available as single units or multi-drive tape libraries
	with 6 drives and 120 tapes in a single cabinet.  Tapes are changed
	automatically by the unit.  Library capacities reach 840+&nbsp;GB.</para>

      <para>The Exabyte <quote>Mammoth</quote> model supports 12&nbsp;GB on one tape
	(24&nbsp;GB with compression) and costs approximately twice as much as
	conventional tape drives.</para>

      <para>Data is recorded onto the tape using helical-scan, the heads are
	positioned at an angle to the media (approximately 6 degrees).  The
	tape wraps around 270 degrees of the spool that holds the heads.  The
	spool spins while the tape slides over the spool.  The result is a
	high density of data and closely packed tracks that angle across the
	tape from one edge to the other.</para>
    </sect2>

    <sect2 id="backups-tapebackups-qic">
      <title>QIC</title>
      <indexterm>
        <primary>tape media</primary>
	<secondary>QIC-150</secondary>
      </indexterm>

      <para>QIC-150 tapes and drives are, perhaps, the most common tape drive
	and media around.  QIC tape drives are the least expensive <quote>serious</quote>
	backup drives.  The downside is the cost of media.  QIC tapes are
	expensive compared to 8mm or 4mm tapes, up to 5 times the price per GB
	data storage.  But, if your needs can be satisfied with a half-dozen
	tapes, QIC may be the correct choice.  QIC is the
	<emphasis>most</emphasis> common tape drive.  Every site has a QIC
	drive of some density or another.  Therein lies the rub, QIC has a
	large number of densities on physically similar (sometimes identical)
	tapes.  QIC drives are not quiet.  These drives audibly seek before
	they begin to record data and are clearly audible whenever reading,
	writing or seeking.  QIC tapes measure (6 x 4 x 0.7 inches; 15.2 x
	10.2 x 1.7 mm).  <link
	  linkend="backups-tapebackups-mini">Mini-cartridges</link>, which
	also use 1/4" wide tape are discussed separately.  Tape libraries and
	changers are not available.</para>

      <para>Data throughput ranges from ~150&nbsp;kB/s to ~500&nbsp;kB/s.  Data capacity
	ranges from 40&nbsp;MB to 15&nbsp;GB.  Hardware compression is available on many
	of the newer QIC drives.  QIC drives are less frequently installed;
	they are being supplanted by DAT drives.</para>

      <para>Data is recorded onto the tape in tracks.  The tracks run along
	the long axis of the tape media from one end to the other.  The number
	of tracks, and therefore the width of a track, varies with the tape's
	capacity.  Most if not all newer drives provide backward-compatibility
	at least for reading (but often also for writing).  QIC has a good
	reputation regarding the safety of the data (the mechanics are simpler
	and more robust than for helical scan drives).</para>

      <para>Tapes should be retired from use after 5,000 backups.</para>
    </sect2>

    <sect2 id="backups-tapebackups-mini">
      <title>XXX* Mini-Cartridge</title>

      <para></para>
    </sect2>

    <sect2 id="backups-tapebackups-dlt">
      <title>DLT</title>
      <indexterm>
        <primary>tape media</primary>
	<secondary>DLT</secondary>
      </indexterm>

      <para>DLT has the fastest data transfer rate of all the drive types
	listed here.  The 1/2" (12.5mm) tape is contained in a single spool
	cartridge (4 x 4 x 1 inches; 100 x 100 x 25 mm).  The cartridge has a
	swinging gate along one entire side of the cartridge.  The drive
	mechanism opens this gate to extract the tape leader.  The tape leader
	has an oval hole in it which the drive uses to <quote>hook</quote> the tape.  The
	take-up spool is located inside the tape drive.  All the other tape
	cartridges listed here (9 track tapes are the only exception) have
	both the supply and take-up spools located inside the tape cartridge
	itself.</para>

      <para>Data throughput is approximately 1.5&nbsp;MB/s, three times the throughput of
	4mm, 8mm, or QIC tape drives.  Data capacities range from 10&nbsp;GB to 20&nbsp;GB
	for a single drive.  Drives are available in both multi-tape changers
	and multi-tape, multi-drive tape libraries containing from 5 to 900
	tapes over 1 to 20 drives, providing from 50&nbsp;GB to 9&nbsp;TB of
	storage.</para>

      <para>With compression, DLT Type IV format supports up to 70&nbsp;GB
	capacity.</para>

      <para>Data is recorded onto the tape in tracks parallel to the direction
	of travel (just like QIC tapes).  Two tracks are written at once.
	Read/write head lifetimes are relatively long; once the tape stops
	moving, there is no relative motion between the heads and the
	tape.</para>
    </sect2>

    <sect2>
      <title id="backups-tapebackups-ait">AIT</title>
      <indexterm>
        <primary>tape media</primary>
	<secondary>AIT</secondary>
      </indexterm>

      <para>AIT is a new format from Sony, and can hold up to 50&nbsp;GB (with
	compression) per tape.  The tapes contain memory chips which retain an
	index of the tape's contents.  This index can be rapidly read by the
	tape drive to determine the position of files on the tape, instead of
	the several minutes that would be required for other tapes.  Software
	such as <application>SAMS:Alexandria</application> can operate forty or more AIT tape libraries,
	communicating directly with the tape's memory chip to display the
	contents on screen, determine what files were backed up to which
	tape, locate the correct tape, load it, and restore the data from the
	tape.</para>

      <para>Libraries like this cost in the region of $20,000, pricing them a
	little out of the hobbyist market.</para>
    </sect2>

    <sect2>
      <title>Using a New Tape for the First Time</title>

      <para>The first time that you try to read or write a new, completely
	blank tape, the operation will fail.  The console messages should be
	similar to:</para>

      <screen>sa0(ncr1:4:0): NOT READY asc:4,1
sa0(ncr1:4:0):  Logical unit is in process of becoming ready</screen>

      <para>The tape does not contain an Identifier Block (block number 0).
	All QIC tape drives since the adoption of QIC-525 standard write an
	Identifier Block to the tape.  There are two solutions:</para>

      <itemizedlist>
	<listitem>
	  <para><command>mt fsf 1</command> causes the tape drive to write an
	  Identifier Block to the tape.</para>
	</listitem>

	<listitem>
	  <para>Use the front panel button to eject the tape.</para>

	  <para>Re-insert the tape and <command>dump</command> data to
	    the tape.</para>

	  <para><command>dump</command> will report <errorname>DUMP: End of tape
	    detected</errorname> and the console will show: <errorname>HARDWARE
	    FAILURE info:280 asc:80,96</errorname>.</para>

	  <para>rewind the tape using: <command>mt rewind</command>.</para>

	  <para>Subsequent tape operations are successful.</para>
	</listitem>
      </itemizedlist>

    </sect2>
  </sect1>
  
  <sect1 id="backups-floppybackups">
    <title>Backups to Floppies</title>

    <sect2 id="floppies-using">
      <title>Can I Use Floppies for Backing Up My Data?</title>
      <indexterm><primary>backup floppies</primary></indexterm>
      <indexterm><primary>floppy disks</primary></indexterm>

      <para>Floppy disks are not really a suitable media for
        making backups as:</para>

      <itemizedlist>
	<listitem>
	  <para>The media is unreliable, especially over long periods of
	    time.</para>
	</listitem>

	<listitem>
	  <para>Backing up and restoring is very slow.</para>
	</listitem>

	<listitem>
	  <para>They have a very limited capacity (the days of backing up
	    an entire hard disk onto a dozen or so floppies has long since
	    passed).</para>
	</listitem>
      </itemizedlist>

      <para>However, if you have no other method of backing up your data then
	floppy disks are better than no backup at all.</para>

      <para>If you do have to use floppy disks then ensure that you use good
	quality ones. Floppies that have been lying around the office for a
	couple of years are a bad choice. Ideally use new ones from a
	reputable manufacturer.</para>
    </sect2>

    <sect2 id="floppies-creating">
      <title>So How Do I Backup My Data to Floppies?</title>

      <para>The best way to backup to floppy disk is to use
	&man.tar.1; with the <option>-M</option> (multi
	volume) option, which allows backups to span multiple
	floppies.</para>

      <para>To backup all the files in the current directory and sub-directory
	use this (as <username>root</username>):</para>

      <screen>&prompt.root; <userinput>tar Mcvf /dev/fd0 *</userinput></screen>

      <para>When the first floppy is full &man.tar.1; will prompt you to
	insert the next volume (because &man.tar.1; is media independent it
	refers to volumes; in this context it means floppy disk).</para>

      <screen>Prepare volume #2 for /dev/fd0 and hit return:</screen>

      <para>This is repeated (with the volume number incrementing) until all
	the specified files have been archived.</para>
    </sect2>

    <sect2 id="floppies-compress">
      <title>Can I Compress My Backups?</title>
      <indexterm>
        <primary><command>tar</command></primary>
      </indexterm>
      <indexterm>
        <primary><command>gzip</command></primary>
      </indexterm>
      <indexterm><primary>compression</primary></indexterm>

      <para>Unfortunately, &man.tar.1; will not allow the
	<option>-z</option> option to be used for multi-volume archives.
	You could, of course, &man.gzip.1; all the files,
	&man.tar.1; them to the floppies, then
	&man.gunzip.1; the files again!</para>
    </sect2>

    <sect2 id="floppies-restoring">
      <title>How Do I Restore My Backups?</title>

      <para>To restore the entire archive use:</para>

      <screen>&prompt.root; <userinput>tar Mxvf /dev/fd0</userinput></screen>

      <para>There are two ways that you can use to restore only
	specific files.  First, you can start with the first floppy
	and use:</para>

      <screen>&prompt.root; <userinput>tar Mxvf /dev/fd0 <replaceable>filename</replaceable></userinput></screen>

      <para>The utility &man.tar.1; will prompt you to insert subsequent floppies until it
	finds the required file.</para>

      <para>Alternatively, if you know which floppy the file is on then you
	can simply insert that floppy and use the same command as above. Note
	that if the first file on the floppy is a continuation from the
	previous one then &man.tar.1; will warn you that it cannot
	restore it, even if you have not asked it to!</para>
    </sect2>
  </sect1>

  <sect1 id="backup-basics">
    <title>Backup Basics</title>

    <para>The three major backup programs are
	&man.dump.8;,
	&man.tar.1;,
      and
	&man.cpio.1;.</para>

    <sect2>
      <title>Dump and Restore</title>
      <indexterm>
        <primary>backup software</primary>
	<secondary>dump / restore</secondary>
      </indexterm>
      <indexterm><primary><command>dump</command></primary></indexterm>
      <indexterm><primary><command>restore</command></primary></indexterm>

      <para>The traditional &unix; backup programs are
	<command>dump</command> and <command>restore</command>.  They
	operate on the drive as a collection of disk blocks, below the
	abstractions of files, links and directories that are created by
	the file systems. <command>dump</command> backs up an entire
	file system on a device.  It is unable to backup only part of a
	file system or a directory tree that spans more than one
	file system.  <command>dump</command> does not write files and
	directories to tape, but rather writes the raw data blocks that
	comprise files and directories.</para>

      <note><para>If you use <command>dump</command> on your root directory, you
        would not back up <filename>/home</filename>,
        <filename>/usr</filename> or many other directories since
        these are typically mount points for other file systems or
        symbolic links into those file systems.</para></note>

      <para><command>dump</command> has quirks that remain from its early days in
	Version 6 of AT&amp;T UNIX (circa 1975).  The default
	parameters are suitable for 9-track tapes (6250 bpi), not the
	high-density media available today (up to 62,182 ftpi).  These
	defaults must be overridden on the command line to utilize the
	capacity of current tape drives.</para>

      <indexterm><primary><filename>.rhosts</filename></primary></indexterm>
      <para>It is also possible to backup data across the network to a
        tape drive attached to another computer with <command>rdump</command> and
        <command>rrestore</command>.  Both programs rely upon <command>rcmd</command> and
        <command>ruserok</command> to access the remote tape drive.  Therefore,
	the user performing the backup must be listed in the
	<filename>.rhosts</filename> file on the remote computer.  The
        arguments to <command>rdump</command> and <command>rrestore</command> must be suitable
        to use on the remote computer.  When
        <command>rdump</command>ing from a FreeBSD computer to an
        Exabyte tape drive connected to a Sun called
        <hostid>komodo</hostid>, use:</para>

      <screen>&prompt.root; <userinput>/sbin/rdump 0dsbfu 54000 13000 126 komodo:/dev/nsa8 /dev/da0a 2>&amp;1</userinput></screen>

      <para>Beware: there are security implications to
        allowing <filename>.rhosts</filename> authentication.  Evaluate your
        situation carefully.</para>

      <para>It is also possible to use <command>dump</command> and
        <command>restore</command> in a more secure fashion over
        <command>ssh</command>.</para>

      <example>
	<title>Using <command>dump</command> over <application>ssh</application></title>

	<screen>&prompt.root; <userinput>/sbin/dump -0uan -f - /usr | gzip -2 | ssh1 -c blowfish \
          targetuser@targetmachine.example.com dd of=/mybigfiles/dump-usr-l0.gz</userinput></screen>

      </example>

      <para>Or using <command>dump</command>'s built-in method,
        setting the enviroment variable <envar>RSH</envar>:</para>

      <example>
	<title>Using <command>dump</command> over <application>ssh</application> with <envar>RSH</envar> set</title>

	<screen>&prompt.root; <userinput>RSH=/usr/bin/ssh /sbin/dump -0uan -f targetuser@targetmachine.example.com:/dev/sa0</userinput></screen>

      </example>

    </sect2>

    <sect2>
      <title><command>tar</command></title>
      <indexterm>
        <primary>backup software</primary>
        <secondary><command>tar</command></secondary>
      </indexterm>

      <para>&man.tar.1; also dates back to Version 6 of AT&amp;T UNIX
	(circa 1975).  <command>tar</command> operates in cooperation
	with the file system; <command>tar</command> writes files and
	directories to tape. <command>tar</command> does not support the
	full range of options that are available from &man.cpio.1;, but
	<command>tar</command> does not require the unusual command
	pipeline that <command>cpio</command> uses.</para>

      <indexterm><primary><command>tar</command></primary></indexterm>
      <para>Most versions of <command>tar</command> do not support
	backups across the network.  The GNU version of
	<command>tar</command>, which FreeBSD utilizes, supports remote
	devices using the same syntax as <command>rdump</command>.  To
	<command>tar</command> to an Exabyte tape drive connected to a
	Sun called <hostid>komodo</hostid>, use:</para>

      <screen>&prompt.root; <userinput>/usr/bin/tar cf komodo:/dev/nsa8 . 2>&amp;1</userinput></screen>

      <para>For versions without
	remote device support, you can use a pipeline and
	<command>rsh</command> to send the data to a remote tape
	drive.</para>

      <screen>&prompt.root; <userinput>tar cf - . | rsh <replaceable>hostname</replaceable> dd of=<replaceable>tape-device</replaceable> obs=20b</userinput></screen>

      <para>If you are worried about the security of backing up over a
	network you should use the <command>ssh</command> command
	instead of <command>rsh</command>.</para>
    </sect2>

    <sect2>
      <title><command>cpio</command></title>
      <indexterm>
        <primary>backup software</primary>
        <secondary><command>cpio</command></secondary>
      </indexterm>

      <para>&man.cpio.1; is the original &unix; file interchange tape
	program for magnetic media.  <command>cpio</command> has options
	(among many others) to perform byte-swapping, write a number of
	different archive formats, and pipe the data to other programs.
	This last feature makes <command>cpio</command> an excellent
	choice for installation media.  <command>cpio</command> does not
	know how to walk the directory tree and a list of files must be
	provided through <filename>stdin</filename>.</para>
      <indexterm><primary><command>cpio</command></primary></indexterm>

      <para><command>cpio</command> does not support backups across
	the network.  You can use a pipeline and <command>rsh</command>
	to send the data to a remote tape drive.</para>

      <screen>&prompt.root; <userinput>for f in <replaceable>directory_list; do</replaceable></userinput>
<userinput>find $f >> backup.list</userinput>
<userinput>done</userinput>
&prompt.root; <userinput>cpio -v -o --format=newc < backup.list | ssh <replaceable>user</replaceable>@<replaceable>host</replaceable> "cat > <replaceable>backup_device</replaceable>"</userinput></screen>

      <para>Where <replaceable>directory_list</replaceable> is the list of
	directories you want to back up,
	<replaceable>user</replaceable>@<replaceable>host</replaceable> is the
	user/hostname combination that will be performing the backups, and
	<replaceable>backup_device</replaceable> is where the backups should
	be written to (e.g., <filename>/dev/nsa0</filename>).</para>
    </sect2>

    <sect2>
      <title><command>pax</command></title>
      <indexterm>
        <primary>backup software</primary>
        <secondary><command>pax</command></secondary>
      </indexterm>
      <indexterm><primary><command>pax</command></primary></indexterm>
      <indexterm><primary>POSIX</primary></indexterm>
      <indexterm><primary>IEEE</primary></indexterm>

      <para>&man.pax.1; is IEEE/&posix;'s answer to
	<command>tar</command> and <command>cpio</command>.  Over the
	years the various versions of <command>tar</command> and
	<command>cpio</command> have gotten slightly incompatible.  So
	rather than fight it out to fully standardize them, &posix;
	created a new archive utility. <command>pax</command> attempts
	to read and write many of the various <command>cpio</command>
	and <command>tar</command> formats, plus new formats of its own.
	Its command set more resembles <command>cpio</command> than
	<command>tar</command>.</para>
    </sect2>

    <sect2 id="backups-programs-amanda">
      <title><application>Amanda</application></title>
      <indexterm>
        <primary>backup software</primary>
        <secondary><application>Amanda</application></secondary>
      </indexterm>
      <indexterm><primary><application>Amanda</application></primary></indexterm>

      <!-- Remove link until <port> tag is available -->
      <para><application>Amanda</application> (Advanced Maryland
        Network Disk Archiver) is a client/server backup system,
        rather than a single program.  An <application>Amanda</application> server will backup to
        a single tape drive any number of computers that have <application>Amanda</application>
        clients and a network connection to the <application>Amanda</application> server.  A
        common problem at sites with a number of large disks is
        that the length of time required to backup to data directly to tape
        exceeds the amount of time available for the task.  <application>Amanda</application>
        solves this problem.  <application>Amanda</application> can use a <quote>holding disk</quote> to
        backup several file systems at the same time.  <application>Amanda</application> creates
        <quote>archive sets</quote>: a group of tapes used over a period of time to
        create full backups of all the file systems listed in <application>Amanda</application>'s
        configuration file.  The <quote>archive set</quote> also contains nightly
        incremental (or differential) backups of all the file systems.
        Restoring a damaged file system requires the most recent full
        backup and the incremental backups.</para>

      <para>The configuration file provides fine control of backups and the
	network traffic that <application>Amanda</application> generates.  <application>Amanda</application> will use any of the
	above backup programs to write the data to tape.  <application>Amanda</application> is available
	as either a port or a package, it is not installed by default.</para>
      </sect2>

    <sect2>
      <title>Do Nothing</title>

      <para><quote>Do nothing</quote> is not a computer program, but it is the
	most widely used backup strategy.  There are no initial costs.  There
	is no backup schedule to follow.  Just say no.  If something happens
	to your data, grin and bear it!</para>

      <para>If your time and your data is worth little to nothing, then
	<quote>Do nothing</quote> is the most suitable backup program for your
	computer.  But beware, &unix; is a useful tool, you may find that within
	six months you have a collection of files that are valuable to
	you.</para>

      <para><quote>Do nothing</quote> is the correct backup method for
	<filename>/usr/obj</filename> and other directory trees that can be
	exactly recreated by your computer.  An example is the files that
	comprise the HTML or &postscript; version of this Handbook.
	These document formats have been created from SGML input
	files.  Creating backups of the HTML or &postscript; files is
	not necessary.  The SGML files are backed up regularly.</para>
    </sect2>

    <sect2>
      <title>Which Backup Program Is Best?</title>
      <indexterm>
        <primary>LISA</primary>
      </indexterm>

      <para>&man.dump.8; <emphasis>Period.</emphasis> Elizabeth D. Zwicky
	torture tested all the backup programs discussed here.  The clear
	choice for preserving all your data and all the peculiarities of &unix;
	file systems is <command>dump</command>.  Elizabeth created file systems containing
	a large variety of unusual conditions (and some not so unusual ones)
	and tested each program by doing a backup and restore of those
	file systems.  The peculiarities included: files with holes, files with
	holes and a block of nulls, files with funny characters in their
	names, unreadable and unwritable files, devices, files that change
	size during the backup, files that are created/deleted during the
	backup and more.  She presented the results at LISA V in Oct. 1991.
	See <ulink
	  url="http://berdmann.dyndns.org/zwicky/testdump.doc.html">torture-testing
	  Backup and Archive Programs</ulink>.</para>
    </sect2>

    <sect2>
      <title>Emergency Restore Procedure</title>

      <sect3>
	<title>Before the Disaster</title>

	<para>There are only four steps that you need to perform in
	  preparation for any disaster that may occur.</para>
	<indexterm>
    <primary><command>disklabel</command></primary>
  </indexterm>

	<para>First, print the disklabel from each of your disks
	  (e.g. <command>disklabel da0 | lpr</command>), your file system table
	  (<filename>/etc/fstab</filename>) and all boot messages,
	  two copies of
	  each.</para>

	<indexterm><primary>fix-it floppies</primary></indexterm>
	<para>Second, determine that the boot and fix-it floppies
	  (<filename>boot.flp</filename> and <filename>fixit.flp</filename>)
	  have all your devices.  The easiest way to check is to reboot your
	  machine with the boot floppy in the floppy drive and check the boot
	  messages.  If all your devices are listed and functional, skip on to
	  step three.</para>

	<para>Otherwise, you have to create two custom bootable
	  floppies which have a kernel that can mount all of your disks
	  and access your tape drive.  These floppies must contain:
	  <command>fdisk</command>, <command>disklabel</command>,
	  <command>newfs</command>, <command>mount</command>, and
	  whichever backup program you use.  These programs must be
	  statically linked.  If you use <command>dump</command>, the
	  floppy must contain <command>restore</command>.</para>

	<para>Third, create backup tapes regularly.  Any changes that you make
	  after your last backup may be irretrievably lost.  Write-protect the
	  backup tapes.</para>

	<para>Fourth, test the floppies (either <filename>boot.flp</filename>
	  and <filename>fixit.flp</filename> or the two custom bootable
	  floppies you made in step two.) and backup tapes.  Make notes of the
	  procedure.  Store these notes with the bootable floppy, the
	  printouts and the backup tapes.  You will be so distraught when
	  restoring that the notes may prevent you from destroying your backup
	  tapes (How? In place of <command>tar xvf /dev/sa0</command>, you
	  might accidentally type <command>tar cvf /dev/sa0</command> and
	  over-write your backup tape).</para>

	<para>For an added measure of security, make bootable floppies and two
	  backup tapes each time.  Store one of each at a remote location.  A
	  remote location is NOT the basement of the same office building.  A
	  number of firms in the World Trade Center learned this lesson the
	  hard way.  A remote location should be physically separated from
	  your computers and disk drives by a significant distance.</para>

	<example>
	  <title>A Script for Creating a Bootable Floppy</title>

	<programlisting><![ CDATA [#!/bin/sh
#
# create a restore floppy
#
# format the floppy
#
PATH=/bin:/sbin:/usr/sbin:/usr/bin

fdformat -q fd0
if [ $? -ne 0 ]
then
	 echo "Bad floppy, please use a new one"
	 exit 1
fi

# place boot blocks on the floppy
#
disklabel -w -B /dev/fd0c fd1440

#
# newfs the one and only partition
#
newfs -t 2 -u 18 -l 1 -c 40 -i 5120 -m 5 -o space /dev/fd0a

#
# mount the new floppy
#
mount /dev/fd0a /mnt

#
# create required directories
#
mkdir /mnt/dev
mkdir /mnt/bin
mkdir /mnt/sbin
mkdir /mnt/etc
mkdir /mnt/root
mkdir /mnt/mnt			# for the root partition
mkdir /mnt/tmp
mkdir /mnt/var

#
# populate the directories
#
if [ ! -x /sys/compile/MINI/kernel ]
then
	 cat << EOM
The MINI kernel does not exist, please create one.
Here is an example config file:
#
# MINI -- A kernel to get FreeBSD onto a disk.
#
machine         "i386"
cpu             "I486_CPU"
ident           MINI
maxusers        5

options         INET                    # needed for _tcp _icmpstat _ipstat
                                        #            _udpstat _tcpstat _udb
options         FFS                     #Berkeley Fast File System
options         FAT_CURSOR              #block cursor in syscons or pccons
options         SCSI_DELAY=15           #Be pessimistic about Joe SCSI device
options         NCONS=2                 #1 virtual consoles
options         USERCONFIG              #Allow user configuration with -c XXX

config          kernel	root on da0 swap on da0 and da1 dumps on da0

device          isa0
device          pci0

device          fdc0	at isa? port "IO_FD1" bio irq 6 drq 2 vector fdintr
device          fd0	at fdc0 drive 0

device          ncr0

device          scbus0

device          sc0	at isa? port "IO_KBD" tty irq 1 vector scintr
device          npx0	at isa? port "IO_NPX" irq 13 vector npxintr

device          da0
device          da1
device          da2

device          sa0

pseudo-device   loop            # required by INET
pseudo-device   gzip            # Exec gzipped a.out's
EOM
	 exit 1
fi

cp -f /sys/compile/MINI/kernel /mnt

gzip -c -best /sbin/init > /mnt/sbin/init
gzip -c -best /sbin/fsck > /mnt/sbin/fsck
gzip -c -best /sbin/mount > /mnt/sbin/mount
gzip -c -best /sbin/halt > /mnt/sbin/halt
gzip -c -best /sbin/restore > /mnt/sbin/restore

gzip -c -best /bin/sh > /mnt/bin/sh
gzip -c -best /bin/sync > /mnt/bin/sync

cp /root/.profile /mnt/root

cp -f /dev/MAKEDEV /mnt/dev
chmod 755 /mnt/dev/MAKEDEV

chmod 500 /mnt/sbin/init
chmod 555 /mnt/sbin/fsck /mnt/sbin/mount /mnt/sbin/halt
chmod 555 /mnt/bin/sh /mnt/bin/sync
chmod 6555 /mnt/sbin/restore

#
# create the devices nodes
#
cd /mnt/dev
./MAKEDEV std
./MAKEDEV da0
./MAKEDEV da1
./MAKEDEV da2
./MAKEDEV sa0
./MAKEDEV pty0
cd /

#
# create minimum file system table
#
cat > /mnt/etc/fstab <<EOM
/dev/fd0a    /    ufs    rw  1  1
EOM

#
# create minimum passwd file
#
cat > /mnt/etc/passwd <<EOM
root:*:0:0:Charlie &:/root:/bin/sh
EOM

cat > /mnt/etc/master.passwd <<EOM
root::0:0::0:0:Charlie &:/root:/bin/sh
EOM

chmod 600 /mnt/etc/master.passwd
chmod 644 /mnt/etc/passwd
/usr/sbin/pwd_mkdb -d/mnt/etc /mnt/etc/master.passwd

#
# umount the floppy and inform the user
#
/sbin/umount /mnt
echo "The floppy has been unmounted and is now ready."]]></programlisting>

        </example>

      </sect3>

      <sect3>
	<title>After the Disaster</title>

	<para>The key question is: did your hardware survive?  You have been
	  doing regular backups so there is no need to worry about the
	  software.</para>

	<para>If the hardware has been damaged, the parts should be replaced
	  before attempting to use the computer.</para>

	<para>If your hardware is okay, check your floppies.  If you are using
	  a custom boot floppy, boot single-user (type <literal>-s</literal>
	  at the <prompt>boot:</prompt> prompt).  Skip the following
	  paragraph.</para>

	<para>If you are using the <filename>boot.flp</filename> and
	  <filename>fixit.flp</filename> floppies, keep reading.  Insert the
	  <filename>boot.flp</filename> floppy in the first floppy drive and
	  boot the computer.  The original install menu will be displayed on
	  the screen.  Select the <literal>Fixit--Repair mode with CDROM or
	    floppy.</literal> option.  Insert the
	  <filename>fixit.flp</filename> when prompted.
	  <command>restore</command> and the other programs that you need are
	  located in <filename>/mnt2/stand</filename>.</para>

	<para>Recover each file system separately.</para>

	<indexterm>
    <primary><command>mount</command></primary>
  </indexterm>
	<indexterm><primary>root partition</primary></indexterm>
	<indexterm>
    <primary><command>disklabel</command></primary>
  </indexterm>
	<indexterm>
    <primary><command>newfs</command></primary>
  </indexterm>
	<para>Try to <command>mount</command> (e.g. <command>mount /dev/da0a
	    /mnt</command>)  the root partition of your first disk.  If the
	  disklabel was damaged, use <command>disklabel</command> to re-partition and
	  label the disk to match the label that you printed and saved.  Use
	    <command>newfs</command> to re-create the file systems.  Re-mount the root
	  partition of the floppy read-write (<command>mount -u -o rw
	    /mnt</command>).  Use your backup program and backup tapes to
	  recover the data for this file system (e.g. <command>restore vrf
	    /dev/sa0</command>).  Unmount the file system (e.g. <command>umount
	    /mnt</command>). Repeat for each file system that was
	  damaged.</para>

	<para>Once your system is running, backup your data onto new tapes.
	  Whatever caused the crash or data loss may strike again.  Another
	  hour spent now may save you from further distress later.</para>
      </sect3>

<![ %not.published; [

      <sect3>
	<title>* I Did Not Prepare for the Disaster, What Now?</title>

	<para></para>
      </sect3>
]]>

    </sect2>
  </sect1>

  <sect1 id="disks-virtual">
    <sect1info>
      <authorgroup>
	<author>
	  <firstname>Marc</firstname>
	  <surname>Fonvieille</surname>
	  <contrib>Reorganized and enhanced by </contrib>
	</author>
      </authorgroup>
    </sect1info>
    <title>Network, Memory, and File-Backed File Systems</title>
    <indexterm><primary>virtual disks</primary></indexterm>
    <indexterm>
      <primary>disks</primary>
      <secondary>virtual</secondary>
    </indexterm>

    <para>Aside from the disks you physically insert into your computer:
      floppies, CDs, hard drives, and so forth; other forms of disks
      are understood by FreeBSD - the <firstterm>virtual
      disks</firstterm>.</para>

    <indexterm><primary>NFS</primary></indexterm>
    <indexterm><primary>Coda</primary></indexterm>
    <indexterm>
      <primary>disks</primary>
      <secondary>memory</secondary>
    </indexterm>
    <para>These include network file systems such as the <link
	linkend="network-nfs">Network File System</link> and Coda, memory-based
      file systems and
      file-backed file systems.</para>

    <para>According to the FreeBSD version you run, you will have to use
      different tools for creation and use of file-backed and
      memory-based file systems.</para>

    <note>
      <para>The FreeBSD&nbsp;4.X users will have to use &man.MAKEDEV.8;
	to create the required devices.  FreeBSD&nbsp;5.0 and later use
	&man.devfs.5; to allocate device nodes transparently for the
	user.</para>
    </note>

    <sect2 id="disks-vnconfig">
      <title>File-Backed File System under FreeBSD&nbsp;4.X</title>
      <indexterm>
        <primary>disks</primary>
        <secondary>file-backed (4.X)</secondary>
      </indexterm>

      <para>The utility &man.vnconfig.8; configures and enables vnode pseudo-disk
	devices.  A <firstterm>vnode</firstterm> is a representation
	of a file, and is the focus of file activity.  This means that
	&man.vnconfig.8; uses files to create and operate a
	file system.  One possible use is the mounting of floppy or CD
	images kept in files.</para>

      <para>To use &man.vnconfig.8;, you need &man.vn.4; support in your
	kernel configuration file:</para>

      <programlisting>pseudo-device vn</programlisting>

      <para>To mount an existing file system image:</para>

      <example>
	<title>Using vnconfig to Mount an Existing File System
	  Image under FreeBSD&nbsp;4.X</title>

	<screen>&prompt.root; <userinput>vnconfig vn<replaceable>0</replaceable> <replaceable>diskimage</replaceable></userinput>
&prompt.root; <userinput>mount /dev/vn<replaceable>0</replaceable>c <replaceable>/mnt</replaceable></userinput></screen>
      </example>

      <para>To create a new file system image with &man.vnconfig.8;:</para>

      <example>
	<title>Creating a New File-Backed Disk with <command>vnconfig</command></title>
	
	<screen>&prompt.root; <userinput>dd if=/dev/zero of=<replaceable>newimage</replaceable> bs=1k count=<replaceable>5</replaceable>k</userinput>
5120+0 records in
5120+0 records out
&prompt.root; <userinput>vnconfig -s labels -c vn<replaceable>0</replaceable> <replaceable>newimage</replaceable></userinput>
&prompt.root; <userinput>disklabel -r -w vn<replaceable>0</replaceable> auto</userinput>
&prompt.root; <userinput>newfs vn<replaceable>0</replaceable>c</userinput>
Warning: 2048 sector(s) in last cylinder unallocated
/dev/vn0c:     10240 sectors in 3 cylinders of 1 tracks, 4096 sectors
        5.0MB in 1 cyl groups (16 c/g, 32.00MB/g, 1280 i/g)
super-block backups (for fsck -b #) at:
 32
&prompt.root; <userinput>mount /dev/vn<replaceable>0</replaceable>c <replaceable>/mnt</replaceable></userinput>
&prompt.root; <userinput>df <replaceable>/mnt</replaceable></userinput>
Filesystem  1K-blocks     Used    Avail Capacity  Mounted on
/dev/vn0c        4927        1     4532     0%    /mnt</screen>
      </example>
    </sect2>

    <sect2 id="disks-mdconfig">
      <title>File-Backed File System under FreeBSD&nbsp;5.X</title>
      <indexterm>
        <primary>disks</primary>
        <secondary>file-backed (5.X)</secondary>
      </indexterm>

      <para>The utility &man.mdconfig.8; is used to configure and enable
	memory disks, &man.md.4;, under FreeBSD&nbsp;5.X.  To use
	&man.mdconfig.8;, you have to load &man.md.4; module or to add
	the support in your kernel configuration file:</para>

      <programlisting>device md</programlisting>

      <para>The &man.mdconfig.8; command supports three kinds of
	memory backed virtual disks: memory disks allocated with
	&man.malloc.9;, memory disks using a file or swap space as
	backing.  One possible use is the mounting of floppy
	or CD images kept in files.</para>

      <para>To mount an existing file system image:</para>

      <example>
	<title>Using <command>mdconfig</command> to Mount an Existing File System
	  Image under FreeBSD&nbsp;5.X</title>

	<screen>&prompt.root; <userinput>mdconfig -a -t vnode -f <replaceable>diskimage</replaceable> -u <replaceable>0</replaceable></userinput>
&prompt.root; <userinput>mount /dev/md<replaceable>0</replaceable>c <replaceable>/mnt</replaceable></userinput></screen>
      </example>

      <para>To create a new file system image with &man.mdconfig.8;:</para>

      <example>
	<title>Creating a New File-Backed Disk with <command>mdconfig</command></title>
	
	<screen>&prompt.root; <userinput>dd if=/dev/zero of=<replaceable>newimage</replaceable> bs=1k count=<replaceable>5</replaceable>k</userinput>
5120+0 records in
5120+0 records out
&prompt.root; <userinput>mdconfig -a -t vnode -f <replaceable>newimage</replaceable> -u <replaceable>0</replaceable></userinput>
&prompt.root; <userinput>disklabel -r -w md<replaceable>0</replaceable> auto</userinput>
&prompt.root; <userinput>newfs md<replaceable>0</replaceable>c</userinput>
/dev/md0c: 5.0MB (10240 sectors) block size 16384, fragment size 2048
	using 4 cylinder groups of 1.27MB, 81 blks, 256 inodes.
super-block backups (for fsck -b #) at:
 32, 2624, 5216, 7808
&prompt.root; <userinput>mount /dev/md<replaceable>0</replaceable>c <replaceable>/mnt</replaceable></userinput>
&prompt.root; <userinput>df <replaceable>/mnt</replaceable></userinput>
Filesystem  1K-blocks     Used    Avail Capacity  Mounted on
/dev/md0c        4846        2     4458     0%    /mnt</screen>
      </example>

      <para>If you do not specify the unit number with the
	<option>-u</option> option, &man.mdconfig.8; will use the
	&man.md.4; automatic allocation to select an unused device.
	The name of the allocated unit will be output on stdout like
	<devicename>md4</devicename>.  For more details about
	&man.mdconfig.8;, please refer to the manual page.</para>

      <note><para>Since &os;&nbsp;5.1-RELEASE, the &man.bsdlabel.8;
	utility replaces the old &man.disklabel.8; program.  With
	&man.bsdlabel.8; a number of obsolete options and parameters
	have been retired; in the example above the option
	<option>-r</option> should be removed.  For more
	information, please refer to the &man.bsdlabel.8;
	manual page.</para></note>

      <para>The utility &man.mdconfig.8; is very useful, however it
	asks many command lines to create a file-backed file system.
	FreeBSD&nbsp;5.0 also comes with a tool called &man.mdmfs.8;,
	this program configures a &man.md.4; disk using
	&man.mdconfig.8;, puts a UFS file system on it using
	&man.newfs.8;, and mounts it using &man.mount.8;.  For example,
	if you want to create and mount the same file system image as
	above, simply type the following:</para>

      <example>
	<title>Configure and Mount a File-Backed Disk with <command>mdmfs</command></title>
	<screen>&prompt.root; <userinput>dd if=/dev/zero of=<replaceable>newimage</replaceable> bs=1k count=<replaceable>5</replaceable>k</userinput>
5120+0 records in
5120+0 records out
&prompt.root; <userinput>mdmfs -F <replaceable>newimage</replaceable> -s <replaceable>5</replaceable>m md<replaceable>0</replaceable> <replaceable>/mnt</replaceable></userinput>
&prompt.root; <userinput>df <replaceable>/mnt</replaceable></userinput>
Filesystem 1K-blocks Used Avail Capacity  Mounted on
/dev/md0        4846    2  4458     0%    /mnt</screen>
      </example>

      <para>If you use the option <option>md</option> without unit
	number, &man.mdmfs.8; will use &man.md.4; auto-unit feature to
	automatically select an unused device.  For more details
	about &man.mdmfs.8;, please refer to the manual page.</para>

    </sect2>

    <sect2 id="disks-md-freebsd4">
      <title>Memory-Based File System under FreeBSD&nbsp;4.X</title>
      <indexterm>
        <primary>disks</primary>
        <secondary>memory file system (4.X)</secondary>
      </indexterm>

      <para>The &man.md.4; driver is a simple, efficient means to create memory
	file systems under FreeBSD&nbsp;4.X. &man.malloc.9; is used
	to allocate the memory.</para>

      <para>Simply take a file system you have prepared with, for
	example, &man.vnconfig.8;, and:</para>

      <example>
	<title>md Memory Disk under FreeBSD&nbsp;4.X</title>

	<screen>&prompt.root; <userinput>dd if=<replaceable>newimage</replaceable> of=/dev/md<replaceable>0</replaceable></userinput>
5120+0 records in
5120+0 records out
&prompt.root; <userinput>mount /dev/md<replaceable>0c</replaceable> <replaceable>/mnt</replaceable></userinput>
&prompt.root; <userinput>df <replaceable>/mnt</replaceable></userinput>
Filesystem  1K-blocks     Used    Avail Capacity  Mounted on
/dev/md0c        4927        1     4532     0%    /mnt</screen>
      </example>

      <para>For more details, please refer to &man.md.4; manual
	page.</para>
    </sect2>

    <sect2 id="disks-md-freebsd5">
      <title>Memory-Based File System under FreeBSD&nbsp;5.X</title>
      <indexterm>
        <primary>disks</primary>
        <secondary>memory file system (5.X)</secondary>
      </indexterm>

      <para>The same tools are used for memory-based and file-backed
	file systems: &man.mdconfig.8; or &man.mdmfs.8;.  The storage
	for memory-based file system is allocated with
	&man.malloc.9;.</para>

      <example>
	<title>Creating a New Memory-Based Disk with
	  <command>mdconfig</command></title>

	<screen>&prompt.root; <userinput>mdconfig -a -t malloc -s <replaceable>5</replaceable>m -u <replaceable>1</replaceable></userinput>
&prompt.root; <userinput>newfs -U md<replaceable>1</replaceable></userinput>
/dev/md1: 5.0MB (10240 sectors) block size 16384, fragment size 2048
	using 4 cylinder groups of 1.27MB, 81 blks, 256 inodes.
	with soft updates
super-block backups (for fsck -b #) at:
 32, 2624, 5216, 7808
&prompt.root; <userinput>mount /dev/md<replaceable>1</replaceable> <replaceable>/mnt</replaceable></userinput>
&prompt.root; <userinput>df <replaceable>/mnt</replaceable></userinput>
Filesystem 1K-blocks Used Avail Capacity  Mounted on
/dev/md1        4846    2  4458     0%    /mnt</screen>
      </example>

      <example>
	<title>Creating a New Memory-Based Disk with
	  <command>mdmfs</command></title>
	<screen>&prompt.root; <userinput>mdmfs -M -s <replaceable>5</replaceable>m md<replaceable>2</replaceable> <replaceable>/mnt</replaceable></userinput>
&prompt.root; <userinput>df <replaceable>/mnt</replaceable></userinput>
Filesystem 1K-blocks Used Avail Capacity  Mounted on
/dev/md2        4846    2  4458     0%    /mnt</screen>
      </example>

      <para>Instead of using a &man.malloc.9; backed file system, it is
	possible to use swap, for that just replace
	<option>malloc</option> with <option>swap</option> in the
	command line of &man.mdconfig.8;.  The &man.mdmfs.8; utility
	by default (without <option>-M</option>) creates a swap-based
	disk.  For more details, please refer to &man.mdconfig.8;
	and &man.mdmfs.8; manual pages.</para>
    </sect2>

    <sect2>
      <title>Detaching a Memory Disk from the System</title>
      <indexterm>
        <primary>disks</primary>
        <secondary>detaching a memory disk</secondary>
      </indexterm>

      <para>When a memory-based or file-based file system
	is not used, you should release all resources to the system.
	The first thing to do is to unmount the file system, then use
	&man.mdconfig.8; to detach the disk from the system and release
	the resources.</para>

      <para>For example to detach and free all resources used by
	<filename>/dev/md4</filename>:</para>

      <screen>&prompt.root; <userinput>mdconfig -d -u <replaceable>4</replaceable></userinput></screen>

      <para>It is possible to list information about configured
	&man.md.4; devices in using the command <command>mdconfig
	-l</command>.</para>

      <para>For FreeBSD&nbsp;4.X, &man.vnconfig.8; is used to detach
	the device.  For example to detach and free all resources
	used by <filename>/dev/vn4</filename>:</para>

      <screen>&prompt.root; <userinput>vnconfig -u vn<replaceable>4</replaceable></userinput></screen>


    </sect2>
  </sect1>
  
  <sect1 id="snapshots">
    <sect1info>
      <authorgroup>
	<author>
	  <firstname>Tom</firstname>
	  <surname>Rhodes</surname>
	  <contrib>Contributed by </contrib>
	</author>
      </authorgroup>
      <!-- 15 JUL 2002 -->
    </sect1info>

    <title>File System Snapshots</title>

    <indexterm>
      <primary>file systems</primary>
      <secondary>snapshots</secondary>
    </indexterm>
    
      <para>FreeBSD&nbsp;5.0 offers a new feature in conjunction with
	<link linkend="soft-updates">Soft Updates</link>: File system snapshots.</para>

      <para>Snapshots allow a user to create images of specified file
	systems, and treat them as a file.
	Snapshot files must be created in the file system that the
	action is performed on, and a user may create no more than 20
	snapshots per file system.  Active snapshots are recorded
	in the superblock so they are persistent across unmount and
	remount operations along with system reboots.  When a snapshot
	is no longer required, it can be removed with the standard &man.rm.1;
	command.  Snapshots may be removed in any order,
	however all the used space may not be acquired because another snapshot will
	possibly claim some of the released blocks.</para>

      <para>During initial creation, the <option>schg</option> flag (see the &man.chflags.1; manual page)
	is set to ensure that even <username>root</username> cannot write to the snapshot.
	The &man.unlink.1; command makes an exception for snapshot files
	since it allows them to be removed
	with the <option>schg</option> flag set, so it is not necessary to
	clear the <option>schg</option> flag before removing a snapshot file.</para>

      <para>Snapshots are created with the &man.mount.8; command.  To place
	a snapshot of <filename>/var</filename> in the file
	<filename>/var/snapshot/snap</filename> use the following
	command:</para>

<screen>&prompt.root; <userinput>mount -u -o snapshot /var/snapshot/snap /var</userinput></screen>

      <para>Alternatively, you can use &man.mksnap.ffs.8; to create
	a snapshot:</para>
<screen>&prompt.root; <userinput>mksnap_ffs /var /var/snapshot/snap</userinput></screen>

      <para>Once a snapshot has been created, it has several
	uses:</para>

      <itemizedlist>
	<listitem>
	  <para>Some administrators will use a snapshot file for backup purposes,
	    because the snapshot can be transfered to CDs or tape.</para>
	</listitem>
	
	<listitem>
	  <para>File integrity, &man.fsck.8; may be ran on the snapshot.
	    Assuming that the file system was clean when it was mounted, you
	    should always get a clean (and unchanging) result.
	    This is essentially what the
	    background &man.fsck.8; process does.</para>
	</listitem>
	
	<listitem>
	  <para>Run the &man.dump.8; utility on the snapshot.
	    A dump will be returned that is consistent with the
	    file system and the timestamp of the snapshot.  &man.dump.8;
	    can also take a snapshot, create a dump image and then
	    remove the snapshot in one command using the
	    <option>-L</option> flag.</para>
	</listitem>
	
	<listitem>
	  <para>&man.mount.8; the snapshot as a frozen image of the file system.
	    To &man.mount.8; the snapshot
	    <filename>/var/snapshot/snap</filename> run:</para>

<screen>&prompt.root; <userinput>mdconfig -a -t vnode -f /var/snapshot/snap -u 4</userinput>
&prompt.root; <userinput>mount -r /dev/md4 /mnt</userinput></screen>

	</listitem>
      </itemizedlist>

      <para>You can now walk the hierarchy of your frozen <filename>/var</filename>
	file system mounted at <filename>/mnt</filename>.  Everything will
	be in the same state it was during the snapshot creation time.
	The only exception is that any earlier snapshots will appear
	as zero length files.  When the use of a snapshot has delimited,
	it can be unmounted with:</para>

<screen>&prompt.root; <userinput>umount /mnt</userinput>
&prompt.root; <userinput>mdconfig -d -u 4</userinput></screen>

      <para>For more information about <option>softupdates</option> and
	file system snapshots, including technical papers, you can visit
	Marshall Kirk McKusick's website at
	<ulink url="http://www.mckusick.com/">http://www.mckusick.com.</ulink></para>
  </sect1>
  
  <sect1 id="quotas">
    <title>File System Quotas</title>
    <indexterm>
      <primary>accounting</primary>
      <secondary>disk space</secondary>
    </indexterm>
    <indexterm><primary>disk quotas</primary></indexterm>

    <para>Quotas are an optional feature of the operating system that
      allow you to limit the amount of disk space and/or the number of
      files a user or members of a group may allocate on a per-file
      system basis. This is used most often on timesharing systems where
      it is desirable to limit the amount of resources any one user or
      group of users may allocate.  This will prevent one user or group
      of users from consuming all of the available disk space.</para>

    <sect2>
      <title>Configuring Your System to Enable Disk Quotas</title>

      <para>Before attempting to use disk quotas, it is necessary to make
	sure that quotas are configured in your kernel.  This is done by
	adding the following line to your kernel configuration
	file:</para>

      <programlisting>options QUOTA</programlisting>

      <para>The stock <filename>GENERIC</filename> kernel does not have
	this enabled by default, so you will have to configure, build and
	install a custom kernel in order to use disk quotas.  Please refer
	to <xref linkend="kernelconfig"> for more information on kernel
	configuration.</para>

      <para>Next you will need to enable disk quotas in
	<filename>/etc/rc.conf</filename>.  This is done by adding the
	line:</para>

      <programlisting>enable_quotas="YES"</programlisting>
      <indexterm>
        <primary>disk quotas</primary>
        <secondary>checking</secondary>
      </indexterm>
      <para>For finer control over your quota startup, there is an
	additional configuration variable available. Normally on bootup,
	the quota integrity of each file system is checked by the
	&man.quotacheck.8; program.  The
	&man.quotacheck.8; facility insures that the data in
	the quota database properly reflects the data on the file system.
	This is a very time consuming process that will significantly
	affect the time your system takes to boot. If you would like to
	skip this step, a variable in <filename>/etc/rc.conf</filename>
	is made available for the purpose:</para>

      <programlisting>check_quotas="NO"</programlisting>

      <para>If you are running FreeBSD prior to 3.2-RELEASE, the
	configuration is simpler, and consists of only one variable.  Set
	the following in your <filename>/etc/rc.conf</filename>:</para>

      <programlisting>check_quotas="YES"</programlisting>

      <para>Finally you will need to edit <filename>/etc/fstab</filename>
	to enable disk quotas on a per-file system basis.  This is where
	you can either enable user or group quotas or both for all of your
	file systems.</para>

      <para>To enable per-user quotas on a file system, add the
	<option>userquota</option> option to the options field in the
	<filename>/etc/fstab</filename> entry for the file system you want
	to enable quotas on.  For example:</para>

      <programlisting>/dev/da1s2g   /home    ufs rw,userquota 1 2</programlisting>

      <para>Similarly, to enable group quotas, use the
	<option>groupquota</option> option instead of
	<option>userquota</option>.  To enable both user and
	group quotas, change the entry as follows:</para>

      <programlisting>/dev/da1s2g    /home    ufs rw,userquota,groupquota 1 2</programlisting>

      <para>By default, the quota files are stored in the root directory of
	the file system with the names <filename>quota.user</filename> and
	<filename>quota.group</filename> for user and group quotas
	respectively.  See &man.fstab.5; for more
	information.  Even though the &man.fstab.5; manual page says that
	you can specify
	an alternate location for the quota files, this is not recommended
	because the various quota utilities do not seem to handle this
	properly.</para>

      <para>At this point you should reboot your system with your new
	kernel.  <filename>/etc/rc</filename> will automatically run the
	appropriate commands to  create the initial quota files for all of
	the quotas you enabled in <filename>/etc/fstab</filename>, so
	there is no need to manually create any zero length quota
	files.</para>

      <para>In the normal course of operations you should not be required
	to run the &man.quotacheck.8;,
	&man.quotaon.8;, or &man.quotaoff.8;
	commands manually.  However, you may want to read their manual pages
	just to be familiar with their operation.</para>
    </sect2>

    <sect2>
      <title>Setting Quota Limits</title>
      <indexterm>
        <primary>disk quotas</primary>
        <secondary>limits</secondary>
      </indexterm>

      <para>Once you have configured your system to enable quotas, verify
	that they really are enabled.  An easy way to do this is to
	run:</para>

      <screen>&prompt.root; <userinput>quota -v</userinput></screen>
	  
      <para>You should see a one line summary of disk usage and current
	quota limits for each file system that quotas are enabled
	on.</para>

      <para>You are now ready to start assigning quota limits with the
	&man.edquota.8; command.</para>

      <para>You have several options on how to enforce limits on the
	amount of disk space a user or group may allocate, and how many
	files they may create.  You may limit allocations based on disk
	space (block quotas) or number of files (inode quotas) or a
	combination of both.  Each of these limits are further broken down
	into two categories: hard and soft limits.</para>

      <indexterm><primary>hard limit</primary></indexterm>
      <para>A hard limit may not be exceeded.  Once a user reaches his
	hard limit he may not make any further allocations on the file
	system in question.  For example, if the user has a hard limit of
	500 blocks on a file system and is currently using 490 blocks, the
	user can only allocate an additional 10 blocks.  Attempting to
	allocate an additional 11 blocks will fail.</para>

      <indexterm><primary>soft limit</primary></indexterm>
      <para>Soft limits, on the other hand, can be exceeded for a limited
	amount of time.  This period of time is known as the grace period,
	which is one week by default.  If a user stays over his or her
	soft limit longer than the grace period, the soft limit will
	turn into a hard limit and no further allocations will be allowed.
	When the user drops back below the soft limit, the grace period
	will be reset.</para>

      <para>The following is an example of what you might see when you run
	the &man.edquota.8; command.  When the
	&man.edquota.8; command is invoked, you are placed into
	the editor specified by the <envar>EDITOR</envar> environment
	variable, or in the <application>vi</application> editor if the
	<envar>EDITOR</envar> variable is not set, to allow you to edit
	the quota limits.</para>

      <screen>&prompt.root; <userinput>edquota -u test</userinput></screen>

      <programlisting>Quotas for user test:
/usr: blocks in use: 65, limits (soft = 50, hard = 75)
        inodes in use: 7, limits (soft = 50, hard = 60)
/usr/var: blocks in use: 0, limits (soft = 50, hard = 75)
        inodes in use: 0, limits (soft = 50, hard = 60)</programlisting>

      <para>You will normally see two lines for each file system that has
	quotas enabled.  One line for the block limits, and one line for
	inode limits.  Simply change the value you want updated to modify
	the quota limit.  For example, to raise this user's block limit
	from a soft limit of 50 and a hard limit of 75 to a soft limit of
	500 and a hard limit of 600, change:</para>

      <programlisting>/usr: blocks in use: 65, limits (soft = 50, hard = 75)</programlisting>

      <para>to:</para>

      <programlisting> /usr: blocks in use: 65, limits (soft = 500, hard = 600)</programlisting>

      <para>The new quota limits will be in place when you exit the
	editor.</para>

      <para>Sometimes it is desirable to set quota limits on a range of
	UIDs.  This can be done by use of the <option>-p</option> option
	on the &man.edquota.8; command.  First, assign the
	desired quota limit to a user, and then run
	<command>edquota -p protouser startuid-enduid</command>.  For
	example, if user <username>test</username> has the desired quota
	limits, the following command can be used to duplicate those quota
	limits for UIDs 10,000 through 19,999:</para>

      <screen>&prompt.root; <userinput>edquota -p test 10000-19999</userinput></screen>
	  
      <para>For more information see &man.edquota.8; manual page.</para>
    </sect2>

    <sect2>
      <title>Checking Quota Limits and Disk Usage</title>
      <indexterm>
        <primary>disk quotas</primary>
        <secondary>checking</secondary>
      </indexterm>

      <para>You can use either the &man.quota.1; or the
	&man.repquota.8; commands to check quota limits and
	disk usage.  The &man.quota.1; command can be used to
	check individual user or group quotas and disk usage.  A user
	may only examine his own quota, and the quota of a group he
	is a member of. Only the super-user may view all user and group
	quotas.  The
	&man.repquota.8; command can be used to get a summary
	of all quotas and disk usage for file systems with quotas
	enabled.</para>

      <para>The following is some sample output from the
	<command>quota -v</command> command for a user that has quota
	limits on two file systems.</para>

      <programlisting>Disk quotas for user test (uid 1002):
     Filesystem  blocks   quota   limit   grace   files   quota   limit   grace
           /usr      65*     50      75   5days       7      50      60
       /usr/var       0      50      75               0      50      60</programlisting>

      <indexterm><primary>grace period</primary></indexterm>
      <para>On the <filename>/usr</filename> file system in the above
	example, this user is currently 15 blocks over the soft limit of
	50 blocks and has 5 days of the grace period left.  Note the
	asterisk <literal>*</literal> which indicates that the user is
	currently over his quota limit.</para>

      <para>Normally file systems that the user is not using any disk
	space on will not show up in the output from the
	&man.quota.1; command, even if he has a quota limit
	assigned for that file system.  The <option>-v</option> option
	will display those file systems, such as the
	<filename>/usr/var</filename> file system in the above
	example.</para>
    </sect2>

    <sect2>
      <title>Quotas over NFS</title>
      <indexterm><primary>NFS</primary></indexterm>

      <para>Quotas are enforced by the quota subsystem on the NFS server.
	The &man.rpc.rquotad.8; daemon makes quota information available
	to the &man.quota.1; command on NFS clients, allowing users on
	those machines to see their quota statistics.</para>

      <para>Enable <command>rpc.rquotad</command> in
	<filename>/etc/inetd.conf</filename> like so:</para>

      <programlisting>rquotad/1      dgram rpc/udp wait root /usr/libexec/rpc.rquotad rpc.rquotad</programlisting>

      <para>Now restart <command>inetd</command>:</para>

      <screen>&prompt.root; <userinput>kill -HUP `cat /var/run/inetd.pid`</userinput></screen>
    </sect2>
  </sect1>
  
  
  <sect1 id="disks-encrypting">
    <sect1info>
      <authorgroup>
	<author>
	  <firstname>Lucky</firstname>
	  <surname>Green</surname>
	  <contrib>Contributed by </contrib>
	  <affiliation>
	    <address><email>shamrock@cypherpunks.to</email></address>
	  </affiliation>
	</author>
      </authorgroup>
      <!-- 11 MARCH 2003 -->
    </sect1info>

    <title>Encrypting Disk Partitions</title>
    <indexterm>
      <primary>disks</primary>
      <secondary>encrypting</secondary></indexterm>

    <para>FreeBSD offers excellent online protections against
      unauthorized data access.  File permissions and Mandatory
      Access Control (MAC) (see <xref linkend="mac">) help prevent
      unauthorized third-parties from accessing data while the operating
      system is active and the computer is powered up. However,
      the permissions enforced by the operating system are irrelevant if an
      attacker has physical access to a computer and can simply move
      the computer's hard drive to another system to copy and analyze
      the sensitive data.</para>

    <para>Regardless of how an attacker may have come into possession of
      a hard drive or powered-down computer, <application>GEOM Based Disk
      Encryption (gbde)</application> can protect the data on the
      computer's file systems against even highly-motivated attackers
      with significant resources. Unlike cumbersome encryption methods
      that encrypt only individual files, <application>gbde</application>
      transparently encrypts entire file systems. No cleartext ever
      touches the hard drive's platter.</para>

    <sect2>
      <title>Enabling gbde in the Kernel</title>

      <procedure>
	<step>
	  <title>Become <username>root</username></title>

	  <para>Configuring <application>gbde</application> requires
	    super-user privileges.</para>

	  <screen>&prompt.user; <userinput>su -</userinput>
Password:</screen>
	</step>
	
	<step>
	  <title>Verify the Operating System Version</title>

	  <para>&man.gbde.4; requires FreeBSD 5.0 or higher.</para>

	  <screen>&prompt.root; <userinput>uname -r</userinput>
5.0-RELEASE</screen>
	</step>

	<step>
	  <title>Add &man.gbde.4; Support to the Kernel Configuration File</title>

	  <para>Using your favorite text editor, add the following
	    line to your kernel configuration file:</para>

	  <para><literal>options GEOM_BDE</literal></para>

	  <para>Configure, recompile, and install the FreeBSD kernel.
	    This process is described in <xref
	    linkend="kernelconfig">.</para>

	  <para>Reboot into the new kernel.</para>
	</step>
      </procedure>
    </sect2>


    <sect2>
      <title>Preparing the Encrypted Hard Drive</title>

      <para>The following example assumes that you are adding a new hard
	drive to your system that will hold a single encrypted partition.
	This partition will be mounted as <filename>/private</filename>.
	<application>gbde</application> can also be used to encrypt
	<filename>/home</filename> and <filename>/var/mail</filename>, but
	this requires more complex instructions which exceed the scope of
	this introduction.</para>

      <procedure>
	<step>
	  <title>Add the New Hard Drive</title>

	  <para>Install the new drive to the system as explained in <xref
	    linkend="disks-adding">. For the purposes of this example,
	    a new hard drive partition has been added as
	    <devicename>/dev/ad4s1c</devicename>. The
	    <devicename>/dev/ad0s1<replaceable>*</replaceable></devicename>
	    devices represent existing standard FreeBSD partitions on
	    the example system.</para>

	  <screen>&prompt.root; <userinput>ls /dev/ad*</userinput>
/dev/ad0        /dev/ad0s1b     /dev/ad0s1e     /dev/ad4s1
/dev/ad0s1      /dev/ad0s1c     /dev/ad0s1f     /dev/ad4s1c
/dev/ad0s1a     /dev/ad0s1d     /dev/ad4</screen>
	</step>

	<step>
	  <title>Create a Directory to Hold gbde Lock Files</title>

	  <screen>&prompt.root; <userinput>mkdir /etc/gbde</userinput></screen>

	  <para>The <application>gbde</application> lock file contains
	    information that <application>gbde</application> requires to
	    access encrypted partitions. Without access to the lock file,
	    <application>gbde</application> will not be able to decrypt
	    the data contained in the encrypted partition without
	    significant manual intervention which is not supported by the
	    software. Each encrypted partition uses a separate lock
	    file.</para>
	</step>

	<step>
	  <title>Initialize the gbde Partition</title>

	  <para>A <application>gbde</application> partition must be
	    initialized before it can be used. This initialization needs to
	    be performed only once:</para>

	  <screen>&prompt.root; <userinput>gbde init /dev/ad4s1c -i -L /etc/gbde/ad4s1c</userinput></screen>

	  <para>&man.gbde.8; will open your editor, permitting you to set
	    various configuration options in a template. For use with UFS1
	    or UFS2, set the sector_size to 2048:</para>

	  <programlisting>$<!-- This is not the space you are looking
for-->FreeBSD: src/sbin/gbde/template.txt,v 1.1 2002/10/20 11:16:13 phk Exp $
#
# Sector size is the smallest unit of data which can be read or written.
# Making it too small decreases performance and decreases available space.
# Making it too large may prevent filesystems from working.  512 is the
# minimum and always safe.  For UFS, use the fragment size
#
sector_size     =       2048
[...]
</programlisting>

	  <para>&man.gbde.8; will ask you twice to type the passphrase that
	    should be used to secure the data. The passphrase must be the
	    same both times. <application>gbde</application>'s ability to
	    protect your data depends entirely on the quality of the
	    passphrase that you choose.
	  <footnote>
          <para>For tips on how to select a secure passphrase that is easy
	    to remember, see the <ulink
	    url="http://world.std.com/~reinhold/diceware.html">Diceware
	    Passphrase</ulink> website.</para></footnote></para>

	  <para>The <command>gbde init</command> command creates a lock
	    file for your <application>gbde</application> partition that in
	    this example is stored as
	    <filename>/etc/gbde/ad4s1c</filename>.</para>

	  <caution>
	    <para><application>gbde</application> lock files
	      <emphasis>must</emphasis> be backed up together with the
	      contents of any encrypted partitions. While deleting a lock
	      file alone cannot prevent a determined attacker from
	      decrypting a <application>gbde</application> partition,
	      without the lock file, the legitimate owner will be unable
	      to access the data on the encrypted partition without a
	      significant amount of work that is totally unsupported by
	      &man.gbde.8; and its designer.</para>
	  </caution>
	</step>

	<step>
	  <title>Attach the Encrypted Partition to the Kernel</title>

	  <screen>&prompt.root; <userinput>gbde attach /dev/ad4s1c -l /etc/gbde/ad4s1c</userinput></screen>

	  <para> You will be asked to provide the passphrase that you
	    selected during the initialization of the encrypted partition.
	    The new encrypted device will show up in
	    <filename>/dev</filename> as
	    <filename>/dev/device_name.bde</filename>:</para>

	  <screen>&prompt.root; <userinput>ls /dev/ad*</userinput>
/dev/ad0        /dev/ad0s1b     /dev/ad0s1e     /dev/ad4s1
/dev/ad0s1      /dev/ad0s1c     /dev/ad0s1f     /dev/ad4s1c
/dev/ad0s1a     /dev/ad0s1d     /dev/ad4        /dev/ad4s1c.bde</screen>
	</step>

	<step>
	  <title>Create a File System on the Encrypted Device</title>

	  <para>Once the encrypted device has been attached to the kernel,
	    you can create a file system on the device. To create a file
	    system on the encrypted device, use &man.newfs.8;. Since it is
	    much faster to initialize a new UFS2 file system than it is to
	    initialize the old UFS1 file system, using &man.newfs.8; with
	    the <option>-O2</option> option is recommended.</para>

	  <note><para>The <option>-O2</option> option is the default
	  with &os;&nbsp;5.1-RELEASE and later.</para></note>

	  <screen>&prompt.root; <userinput>newfs -U -O2 /dev/ad4s1c.bde</userinput></screen>

	  <note>
	    <para>The &man.newfs.8; command must be performed on an
	      attached <application>gbde</application> partition which
	      is identified by a
	      <filename><replaceable>*</replaceable>.bde</filename>
	      extension to the device name.</para>
	  </note>
	</step>

	<step>
	  <title>Mount the Encrypted Partition</title>

	  <para>Create a mount point for the encrypted file system.</para>

	  <screen>&prompt.root; <userinput>mkdir /private</userinput></screen>

	  <para>Mount the encrypted file system.</para>

	  <screen>&prompt.root; <userinput>mount /dev/ad4s1c.bde /private</userinput></screen>
	</step>

	<step>
	  <title>Verify That the Encrypted File System is Available</title>

	  <para>The encrypted file system should now be visible to
	    &man.df.1; and be available for use.</para>

	  <screen>&prompt.user; <userinput>df -H</userinput>
Filesystem        Size   Used  Avail Capacity  Mounted on
/dev/ad0s1a      1037M    72M   883M     8%    /
/devfs            1.0K   1.0K     0B   100%    /dev
/dev/ad0s1f       8.1G    55K   7.5G     0%    /home
/dev/ad0s1e      1037M   1.1M   953M     0%    /tmp
/dev/ad0s1d       6.1G   1.9G   3.7G    35%    /usr
/dev/ad4s1c.bde   150G   4.1K   138G     0%    /private</screen>
	</step>
      </procedure>
    </sect2>

    <sect2>
      <title>Mounting Existing Encrypted File Systems</title>

      <para>After each boot, any encrypted file systems must be
	re-attached to the kernel, checked for errors, and mounted, before
	the file systems can be used. The required commands must be
	executed as user <username>root</username>.</para>

      <procedure>
	<step>
	  <title>Attach the gbde Partition to the Kernel</title>

	  <screen>&prompt.root; <userinput>gbde attach /dev/ad4s1c -l /etc/gbde/ad4s1c</userinput></screen>
	  
	  <para>You will be asked to provide the passphrase that you
	    selected during initialization of the encrypted gbde
	    partition.</para>
	</step>

	<step>
	  <title>Check the File System for Errors</title>

	  <para>Since encrypted file systems cannot yet be listed in
	    <filename>/etc/fstab</filename> for automatic mounting, the
	    file systems must be checked for errors by running &man.fsck.8;
	    manually before mounting.</para>

	  <screen>&prompt.root; <userinput>fsck -p -t ffs /dev/ad4s1c.bde</userinput></screen>
	</step>

	<step>
	  <title>Mount the Encrypted File System</title>

	  <screen>&prompt.root; <userinput>mount /dev/ad4s1c.bde /private</userinput></screen>
	  
	  <para>The encrypted file system is now available for use.</para>
	</step>
      </procedure>

      <sect3>
	<title>Automatically Mounting Encrypted Partitions</title>

	<para>It is possible to create a script to automatically attach,
	  check, and mount an encrypted partition, but for security reasons
	  the script should not contain the &man.gbde.8; password. Instead,
	  it is recommended that such scripts be run manually while
	  providing the password via the console or &man.ssh.1;.</para>
      </sect3>
    </sect2>

      <sect2>
	<title>Cryptographic Protections Employed by gbde</title>

	<para>&man.gbde.8; encrypts the sector payload using 128-bit AES in
	  CBC mode.  Each sector on the disk is encrypted with a different
	  AES key. For more information on <application>gbde</application>'s
	  cryptographic design, including how the sector keys are derived
	  from the user-supplied passphrase, see &man.gbde.4;.</para>
      </sect2>

      <sect2>
	<title>Compatibility Issues</title>

	<para>&man.sysinstall.8; is incompatible with
	  <application>gbde</application>-encrypted devices. All
	  <devicename><replaceable>*</replaceable>.bde</devicename> devices must be detached from the
	  kernel before starting &man.sysinstall.8; or it will crash during
	  its initial probing for devices. To detach the encrypted device
	  used in our example, use the following command:</para>
	<screen>&prompt.root; <userinput>gbde detach /dev/ad4s1c</userinput></screen>

      <para>Also note that, as &man.vinum.4; does not use the
	&man.geom.4; subsystem, you cannot use
	<application>gbde</application> with
	<application>vinum</application> volumes.</para>
      </sect2>

  </sect1>
</chapter>

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