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This patch addresses the following:

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- fixes xref tags

- some tightening and removing of redundancy

- fixed some confusion in glabel section

Approved by	gjb (mentor)
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Dru Lavigne 2013-02-11 14:50:33 +00:00
parent 6a0104e34c
commit 92487e8875
Notes: svn2git 2020-12-08 03:00:23 +00:00 
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1 changed files with 214 additions and 238 deletions

452
en_US.ISO8859-1/books/handbook/geom/chapter.xml
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@ -35,11 +35,11 @@
control utilities which use the framework for configuration.
This chapter will not go into in depth discussion on how GEOM
handles or controls I/O, the underlying subsystem, or code.
This information is provided through the &man.geom.4; manual
page and its various SEE ALSO references. This chapter is also
not a definitive guide to <acronym>RAID</acronym>
configurations. Only GEOM-supported <acronym>RAID</acronym>
classifications will be discussed.</para>
This information is provided in &man.geom.4; and its various
<literal>SEE ALSO</literal> references. This chapter is also
not a definitive guide to <acronym>RAID</acronym> configurations
and only GEOM-supported <acronym>RAID</acronym> classifications
will be discussed.</para>
<para>After reading this chapter, you will know:</para>
@ -70,13 +70,13 @@
<itemizedlist>
<listitem>
<para>Understand how &os; treats disk devices
(<xref linkend="disks"/>).</para>
<para>Understand how &os; treats <link
linkend="disks">disk devices</link>.</para>
</listitem>
<listitem>
<para>Know how to configure and install a new &os; kernel
(<xref linkend="kernelconfig"/>).</para>
<para>Know how to configure and install a new <link
linkend="kernelconfig">&os; kernel</link>.</para>
</listitem>
</itemizedlist>
</sect1>
@ -84,12 +84,12 @@
<sect1 id="GEOM-intro">
<title>GEOM Introduction</title>
<para>GEOM permits access and control to classes &mdash; Master
Boot Records, <acronym>BSD</acronym> labels, etc &mdash; through
the use of providers, or the special files in
<filename class="directory">/dev</filename>. Supporting various
software <acronym>RAID</acronym> configurations, GEOM will
transparently provide access to the operating system and
<para>GEOM permits access and control to classes, such as Master
Boot Records and <acronym>BSD</acronym> labels, through the use
of providers, or the special files in <filename
class="directory">/dev</filename>. By supporting various
software <acronym>RAID</acronym> configurations, GEOM
transparently provides access to the operating system and
operating system utilities.</para>
</sect1>
@ -117,13 +117,13 @@
<primary>Striping</primary>
</indexterm>
<para>Striping is a method used to combine several disk drives
into a single volume. In many cases, this is done through the
use of hardware controllers. The GEOM disk subsystem provides
software support for <acronym>RAID</acronym>0, also known as
disk striping.</para>
<para>Striping combine several disk drives into a single volume.
In many cases, this is done through the use of hardware
controllers. The GEOM disk subsystem provides software support
for <acronym>RAID</acronym>0, also known as disk
striping.</para>
<para>In a <acronym>RAID</acronym>0 system, data are split up in
<para>In a <acronym>RAID</acronym>0 system, data is split into
blocks that get written across all the drives in the array.
Instead of having to wait on the system to write 256k to one
disk, a <acronym>RAID</acronym>0 system can simultaneously write
@ -168,7 +168,7 @@
<para>Determine the device names for the disks which will
be striped, and create the new stripe device. For example,
to stripe two unused and unpartitioned
<acronym>ATA</acronym> disks, for example
<acronym>ATA</acronym> disks with device names of
<filename>/dev/ad2</filename> and
<filename>/dev/ad3</filename>:</para>
@ -179,21 +179,21 @@ Done.</screen>
</step>
<step>
<para>Write a standard label, also known as a partition
table, on the new volume and install the default
bootstrap code:</para>
<para>Write a standard label, also known as a partition table,
on the new volume and install the default bootstrap
code:</para>
<screen>&prompt.root; <userinput>bsdlabel -wB /dev/stripe/st0</userinput></screen>
</step>
<step>
<para>This process should have created two other devices
in the <filename class="directory">/dev/stripe</filename>
directory in addition to the <devicename>st0</devicename>
device. Those include <devicename>st0a</devicename> and
<devicename>st0c</devicename>. At this point a file system
may be created on the <devicename>st0a</devicename> device
with the <command>newfs</command> utility:</para>
<para>This process should create two other devices in
<filename class="directory">/dev/stripe</filename> in
addition to <devicename>st0</devicename>. Those include
<devicename>st0a</devicename> and
<devicename>st0c</devicename>. At this point, a file system
may be created on <devicename>st0a</devicename> using
<command>newfs</command>:</para>
<screen>&prompt.root; <userinput>newfs -U /dev/stripe/st0a</userinput></screen>
@ -209,10 +209,9 @@ Done.</screen>
<para>To mount this striped file system automatically during the
boot process, place the volume information in
<filename>/etc/fstab</filename> file. For this purpose, a
permanent mount point, named
<filename class="directory">stripe</filename>, is
created:</para>
<filename>/etc/fstab</filename>. In this example, a
permanent mount point, named <filename
class="directory">stripe</filename>, is created:</para>
<screen>&prompt.root; <userinput>mkdir /stripe</userinput>
&prompt.root; <userinput>echo "/dev/stripe/st0a /stripe ufs rw 2 2" \</userinput>
@ -249,8 +248,8 @@ Done.</screen>
replace the failed drive without user interruption.</para>
<para>Two common situations are illustrated in these examples.
The first is creating a mirror out of two new drives and using
it as a replacement for an existing single drive. The second
The first creates a mirror out of two new drives and uses it
as a replacement for an existing single drive. The second
example creates a mirror on a single new drive, copies the old
drive's data to it, then inserts the old drive into the
mirror. While this procedure is slightly more complicated, it
@ -317,28 +316,28 @@ Done.</screen>
used to replace the old single disk.</para>
<para>&man.gmirror.8; requires a kernel module,
<filename>geom_mirror.ko</filename>, either built into the
kernel or loaded at boot- or run-time. Manually load the
kernel module now:</para>
<filename>geom_mirror.ko</filename>, either compiled into a
custom kernel or loaded at boot- or run-time. To manually
load the kernel module now:</para>
<screen>&prompt.root; <userinput>gmirror load</userinput></screen>
<para>Create the mirror with the two new drives.</para>
<para>To create the mirror with the two new drives.</para>
<screen>&prompt.root; <userinput>gmirror label -v gm0 /dev/ada1 /dev/ada2</userinput></screen>
<para><devicename>gm0</devicename> is a user-chosen device name
assigned to the new mirror. After the mirror has been
started, this device name will appear in the
<filename>/dev/mirror/</filename> directory.</para>
started, this device name will appear in
<filename>/dev/mirror/</filename>.</para>
<para>MBR and bsdlabel partition tables can now be created on
the mirror with &man.gpart.8;. Here we show a traditional
split-filesystem layout, with partitions for
<filename>/</filename>, swap, <filename>/var</filename>,
<filename>/tmp</filename>, and <filename>/usr</filename>. A
single <filename>/</filename> filesystem and a swap partition
will also work.</para>
single <filename>/</filename> and a swap partition will also
work.</para>
<para>Partitions on the mirror do not have to be the same size
as those on the existing disk, but they must be large enough
@ -384,8 +383,8 @@ Done.</screen>
&prompt.root; <userinput>newfs -U /dev/mirror/gm0s1e</userinput>
&prompt.root; <userinput>newfs -U /dev/mirror/gm0s1f</userinput></screen>
<para>Filesystems from the original disk
(<devicename>ada0</devicename>) can now be copied onto the
<para>Filesystems from the original
<devicename>ada0</devicename> disk can now be copied onto the
mirror with &man.dump.8; and &man.restore.8;.</para>
<screen>&prompt.root; <userinput>mount /dev/mirror/gm0s1a /mnt</userinput>
@ -419,8 +418,8 @@ Done.</screen>
are identical, it does not matter which is selected to
boot.</para>
<para>See the
<link linkend="gmirror-troubleshooting">Troubleshooting</link>
<para>See the <link
linkend="gmirror-troubleshooting">Troubleshooting</link>
section if there are problems booting. Powering down and
disconnecting the original <devicename>ada0</devicename> disk
will allow it to be kept as an offline backup.</para>
@ -432,23 +431,23 @@ Done.</screen>
<sect2>
<title>Creating a Mirror with an Existing Drive</title>
<para>In this example, &os; has already been installed on a
single disk, <devicename>ada0</devicename>. A new disk,
<para>In this example, &os; has been installed on a single
disk, <devicename>ada0</devicename>. A new disk,
<devicename>ada1</devicename>, has been connected to the
system. A one-disk mirror will be created on the new disk,
the existing system copied onto it, and then the old disk will be
inserted into the mirror. This slightly complex procedure is
required because &man.gmirror.8; needs to put a 512-byte block
of metadata at the end of each disk, and the existing
<devicename>ada0</devicename> has usually had all of its space
the existing system copied onto it, and then the old disk will
be inserted into the mirror. This slightly complex procedure
is required because &man.gmirror.8; needs to put a 512-byte
block of metadata at the end of each disk, and the existing
<devicename>ada0</devicename> usually has all of its space
already allocated.</para>
<para>Load the &man.gmirror.8; kernel module.</para>
<para>Load the &man.gmirror.8; kernel module:</para>
<screen>&prompt.root; <userinput>gmirror load</userinput></screen>
<para>Check the media size of the original disk with
&man.diskinfo.8;.</para>
&man.diskinfo.8;:</para>
<screen>&prompt.root; <userinput>diskinfo -v ada0 | head -n3</userinput>
/dev/ada0
@ -461,11 +460,11 @@ Done.</screen>
size. This drive does not store any data, but is used only to
limit the size of the mirror. When &man.gmirror.8; creates
the mirror, it will restrict the capacity to the size of
<devicename>gzero.nop</devicename> even if the new drive
<devicename>gzero.nop</devicename>, even if the new drive
(<devicename>ada1</devicename>) has more space. Note that the
<replaceable>1000204821504</replaceable> in the second line
should be equal to <devicename>ada0</devicename>'s media size
as shown by &man.diskinfo.8; above.</para>
should be equal to the size of <devicename>ada0</devicename>
as shown by &man.diskinfo.8;.</para>
<screen>&prompt.root; <userinput>geom zero load</userinput>
&prompt.root; <userinput>gnop create -s 1000204821504 gzero</userinput>
@ -502,7 +501,7 @@ Done.</screen>
be explained later.</para>
<para>In either case, partition tables on the primary disk
should be copied first. It can be done by using &man.gpart.8;
should be copied first using the &man.gpart.8;
<command>backup</command> and <command>restore</command>
subcommands.</para>
@ -527,8 +526,8 @@ BSD 8
6 freebsd-ufs 130023424 838860800
7 freebsd-ufs 968884224 984640881</screen>
<para>If the whole disk was used in the output of &man.gpart.8;
<command>show</command>, the capacity in these partition
<para>If the whole disk shows as used in the output of
<command>gpart show</command>, the capacity in these partition
tables must be reduced by one sector. Edit the two files,
reducing the size of both the slice and last partition by one.
These are the last numbers in each listing.</para>
@ -550,13 +549,13 @@ BSD 8
disk, these two files can be used without modification.</para>
<para>Now restore the partition table into
<devicename>mirror/gm0</devicename>.</para>
<devicename>mirror/gm0</devicename>:</para>
<screen>&prompt.root; <userinput>gpart restore mirror/gm0 &lt; table.ada0</userinput>
&prompt.root; <userinput>gpart restore mirror/gm0s1 &lt; table.ada0s1</userinput></screen>
<para>Check the partition table with the &man.gpart.8;
<command>show</command>. This example has
<para>Check the partition table with
<command>gpart show</command>. This example has
<devicename>gm0s1a</devicename> for <filename>/</filename>,
<devicename>gm0s1d</devicename> for <filename>/var</filename>,
<devicename>gm0s1e</devicename> for <filename>/usr</filename>,
@ -707,8 +706,7 @@ mirror/gm0 COMPLETE ada1 (ACTIVE)
<para>BIOS settings may have to be changed to boot from one
of the new mirrored drives. Either mirror drive can be
used for booting. As components of a mirror, they contain
identical data.</para>
used for booting as they contain identical data.</para>
</sect4>
<sect4>
@ -742,10 +740,10 @@ mountroot&gt;</screen>
<para>Forgetting to load the
<filename>geom_mirror</filename> module in
<filename>/boot/loader.conf</filename> can cause this
problem. To fix it, boot from a &os;-9 or later CD or USB
stick and choose <literal>Shell</literal> at the first
prompt. Then load the mirror module and mount the mirror
device:</para>
problem. To fix it, boot from a &os;&nbsp;9.0 or later
installation media and choose <literal>Shell</literal> at
the first prompt. Then load the mirror module and mount
the mirror device:</para>
<screen>&prompt.root; <userinput>gmirror load</userinput>
&prompt.root; <userinput>mount /dev/mirror/gm0s1a /mnt</userinput></screen>
@ -759,14 +757,14 @@ mountroot&gt;</screen>
<para>Other problems that cause <literal>error 19</literal>
require more effort to fix. Enter
<literal>ufs:/dev/ada0s1a</literal> at the prompt.
Although the system should boot from
<literal>ufs:/dev/ada0s1a</literal> at the boot loader
prompt. Although the system should boot from
<devicename>ada0</devicename>, another prompt to select a
shell appears because <filename>/etc/fstab</filename> is
incorrect. Press the Enter key at the prompt. Undo the
modifications so far by reverting
<filename>/etc/fstab</filename>, mounting filesystems from
the original disk (<devicename>ada0</devicename>) instead
the original <devicename>ada0</devicename> instead
of the mirror. Reboot the system and try the procedure
again.</para>
@ -780,24 +778,20 @@ mountroot&gt;</screen>
<sect2>
<title>Recovering from Disk Failure</title>
<para>The wonderful part about disk mirroring is that an
individual disk can fail without causing the mirror to lose
any data.</para>
<para>The benefit of disk mirroring is that an individual disk
can fail without causing the mirror to lose any data. In the
above example, if <devicename>ada0</devicename> fails, the
mirror will continue to work, providing data from the
remaining working drive, <devicename>ada1</devicename>.</para>
<para><devicename>ada0</devicename> is one of two drives making
up the mirror in the previous example. If
<devicename>ada0</devicename> fails, the mirror will continue
to work, providing data from the remaining working drive,
<devicename>ada1</devicename>.</para>
<para>To replace the failed drive, the computer is shut down and
the failed drive is physically replaced with a new drive of
equal or greater capacity. Manufacturers use somewhat
arbitrary values when rating drives in gigabytes, and the
only way to really be sure is to compare the total count of
sectors shown by <command>diskinfo -v</command>. A drive with
larger capacity than the mirror will work, although the extra
space on the new drive will not be used.</para>
<para>To replace the failed drive, shut down the system and
physically replace the failed drive with a new drive of equal
or greater capacity. Manufacturers use somewhat arbitrary
values when rating drives in gigabytes, and the only way to
really be sure is to compare the total count of sectors shown
by <command>diskinfo -v</command>. A drive with larger
capacity than the mirror will work, although the extra space
on the new drive will not be used.</para>
<para>After the computer is powered back up, the mirror will be
running in a <quote>degraded</quote> mode with only one drive.
@ -866,18 +860,18 @@ mountroot&gt;</screen>
</indexterm>
<para><acronym>RAID</acronym>3 is a method used to combine several
disk drives into a single volume with a dedicated parity
disk. In a <acronym>RAID</acronym>3 system, data is split up
into a number of bytes that are written across all the drives in
the array except for one disk which acts as a dedicated parity
disk. This means that reading 1024KB from a
disk drives into a single volume with a dedicated parity disk.
In a <acronym>RAID</acronym>3 system, data is split up into a
number of bytes that are written across all the drives in the
array except for one disk which acts as a dedicated parity disk.
This means that reading 1024KB from a
<acronym>RAID</acronym>3 implementation will access all disks in
the array. Performance can be enhanced by using multiple
disk controllers. The <acronym>RAID</acronym>3 array provides a
the array. Performance can be enhanced by using multiple disk
controllers. The <acronym>RAID</acronym>3 array provides a
fault tolerance of 1 drive, while providing a capacity of 1 -
1/n times the total capacity of all drives in the array, where n
is the number of hard drives in the array. Such a configuration
is mostly suitable for storing data of larger sizes, e.g.,
is mostly suitable for storing data of larger sizes such as
multimedia files.</para>
<para>At least 3 physical hard drives are required to build a
@ -885,7 +879,7 @@ mountroot&gt;</screen>
size, since I/O requests are interleaved to read or write to
multiple disks in parallel. Also, due to the nature of
<acronym>RAID</acronym>3, the number of drives must be
equal to 3, 5, 9, 17, etc. (2^n + 1).</para>
equal to 3, 5, 9, 17, and so on, or 2^n + 1.</para>
<sect2>
<title>Creating a Dedicated <acronym>RAID</acronym>3
@ -955,11 +949,7 @@ Done.</screen>
<para>Many numbers will glide across the screen, and after a
bit of time, the process will be complete. The volume has
been created and is ready to be mounted.</para>
</step>
<step>
<para>The last step is to mount the file system:</para>
been created and is ready to be mounted:</para>
<screen>&prompt.root; <userinput>mount /dev/raid3/gr0p1 /multimedia/</userinput></screen>
@ -975,16 +965,16 @@ Done.</screen>
<step>
<para>The <filename>geom_raid3.ko</filename> module must be
loaded before the array can be mounted. To automatically
load the kernel module during the system initialization,
add the following line to the
<filename>/boot/loader.conf</filename> file:</para>
load the kernel module during system initialization, add
the following line to
<filename>/boot/loader.conf</filename>:</para>
<programlisting>geom_raid3_load="YES"</programlisting>
</step>
<step>
<para>The following volume information must be added to the
<filename>/etc/fstab</filename> file in order to
<para>The following volume information must be added to
<filename>/etc/fstab</filename> in order to
automatically mount the array's file system during
the system boot process:</para>
@ -998,7 +988,7 @@ Done.</screen>
<title>GEOM Gate Network Devices</title>
<para>GEOM supports the remote use of devices, such as disks,
CD-ROMs, files, etc. through the use of the gate utilities.
CD-ROMs, and files through the use of the gate utilities.
This is similar to <acronym>NFS</acronym>.</para>
<para>To begin, an exports file must be created. This file
@ -1010,8 +1000,8 @@ Done.</screen>
<programlisting>192.168.1.0/24 RW /dev/da0s4d</programlisting>
<para>It will allow all hosts inside the private network access
the file system on the <devicename>da0s4d</devicename>
<para>This allows all hosts inside the specified private network
access to the file system on the <devicename>da0s4d</devicename>
partition.</para>
<para>To export this device, ensure it is not currently mounted,
@ -1019,25 +1009,24 @@ Done.</screen>
<screen>&prompt.root; <userinput>ggated</userinput></screen>
<para>Now to <command>mount</command> the device on the client
<para>To <command>mount</command> the device on the client
machine, issue the following commands:</para>
<screen>&prompt.root; <userinput>ggatec create -o rw 192.168.1.1 /dev/da0s4d</userinput>
ggate0
&prompt.root; <userinput>mount /dev/ggate0 /mnt</userinput></screen>
<para>From here on, the device may be accessed through the
<filename class="directory">/mnt</filename> mount point.</para>
<para>The device may now be accessed through the <filename
class="directory">/mnt</filename> mount point.</para>
<note>
<para>It should be pointed out that this will fail if the device
is currently mounted on either the server machine or any other
machine on the network.</para>
<para>However, this will fail if the device is currently mounted
on either the server machine or any other machine on the
network.</para>
</note>
<para>When the device is no longer needed, it may be safely
unmounted with the &man.umount.8; command, similar to any other
disk device.</para>
<para>When the device is no longer needed, unmount it with
&man.umount.8;, similar to any other disk device.</para>
</sect1>
<sect1 id="geom-glabel">
@ -1050,34 +1039,32 @@ ggate0
<primary>Disk Labels</primary>
</indexterm>
<para>During system initialization, the &os; kernel will create
<para>During system initialization, the &os; kernel creates
device nodes as devices are found. This method of probing for
devices raises some issues, for instance what if a new disk
device is added via <acronym>USB</acronym>? It is very likely
that a flash device may be handed the device name of
devices raises some issues. For instance, what if a new disk
device is added via <acronym>USB</acronym>? It is likely that
a flash device may be handed the device name of
<devicename>da0</devicename> and the original
<devicename>da0</devicename> shifted to
<devicename>da1</devicename>. This will cause issues mounting
file systems if they are listed in
<filename>/etc/fstab</filename>, effectively, this may also
prevent the system from booting.</para>
<filename>/etc/fstab</filename> which may also prevent the
system from booting.</para>
<para>One solution to this issue is to chain the
<acronym>SCSI</acronym> devices in order so a new device added
to the <acronym>SCSI</acronym> card will be issued unused device
numbers. But what about <acronym>USB</acronym> devices which
may replace the primary <acronym>SCSI</acronym> disk? This
happens because <acronym>USB</acronym> devices are usually
probed before the <acronym>SCSI</acronym> card. One solution is
to only insert these devices after the system has been booted.
Another method could be to use only a single
<acronym>ATA</acronym> drive and never list the
<acronym>SCSI</acronym> devices in
<para>One solution is to chain <acronym>SCSI</acronym> devices
in order so a new device added to the <acronym>SCSI</acronym>
card will be issued unused device numbers. But what about
<acronym>USB</acronym> devices which may replace the primary
<acronym>SCSI</acronym> disk? This happens because
<acronym>USB</acronym> devices are usually probed before the
<acronym>SCSI</acronym> card. One solution is to only insert
these devices after the system has been booted. Another method
is to use only a single <acronym>ATA</acronym> drive and never
list the <acronym>SCSI</acronym> devices in
<filename>/etc/fstab</filename>.</para>
<para>A better solution is available. By using the
<command>glabel</command> utility, an administrator or user may
label their disk devices and use these labels in
<para>A better solution is to use <command>glabel</command> to
label the disk devices and use the labels in
<filename>/etc/fstab</filename>. Because
<command>glabel</command> stores the label in the last sector of
a given provider, the label will remain persistent across
@ -1086,39 +1073,33 @@ ggate0
through.</para>
<note>
<para>This goes without saying that a label be permanent. The
<command>glabel</command> utility may be used to create both a
transient and permanent label. Only the permanent label will
remain consistent across reboots. See the &man.glabel.8;
manual page for more information on the differences between
labels.</para>
<para><command>glabel</command> can create both transient and
permanent labels. Only permanent labels are consistent across
reboots. Refer to &man.glabel.8; for more information on the
differences between labels.</para>
</note>
<sect2>
<title>Label Types and Examples</title>
<para>There are two types of labels, a generic label and a
file system label. Labels can be permanent or temporary.
Permanent labels can be created with the &man.tunefs.8;
or &man.newfs.8; commands. They will then be created
in a sub-directory of
<filename class="directory">/dev</filename>, which will be
named according to their file system type. For example,
<para>Permanent labels can be a generic or a file system label.
Permanent file system labels can be created with
&man.tunefs.8; or &man.newfs.8;. These types of labels are
created in a sub-directory of <filename
class="directory">/dev</filename>, and will be named
according to the file system type. For example,
<acronym>UFS</acronym>2 file system labels will be created in
the <filename class="directory">/dev/ufs</filename> directory.
Permanent labels can also be created with the <command>glabel
label</command> command. These are not file system specific,
and will be created in the
<filename class="directory">/dev/label</filename>
directory.</para>
<filename class="directory">/dev/ufs</filename>. Generic
permanent labels can be created with <command>glabel
label</command>. These are not file system specific and
will be created in <filename
class="directory">/dev/label</filename>.</para>
<para>A temporary label will go away with the next reboot.
These labels will be created in the
<filename class="directory">/dev/label</filename> directory
and are perfect for experimentation. A temporary label can be
created using the <command>glabel create</command> command.
For more information, please read the manual page of
&man.glabel.8;.</para>
<para>Temporary labels are destroyed at the next reboot. These
labels are created in <filename
class="directory">/dev/label</filename> and are suited to
experimentation. A temporary label can be created using
<command>glabel create</command>.</para>
<!-- XXXTR: How do you create a file system label without running newfs
or when there is no newfs (e.g.: cd9660)? -->
@ -1131,14 +1112,12 @@ ggate0
<warning>
<para>If the file system is full, this may cause data
corruption; however, if the file system is full then the
main goal should be removing stale files and not adding
labels.</para>
corruption.</para>
</warning>
<para>A label should now exist in
<filename class="directory">/dev/ufs</filename> which may be
added to <filename>/etc/fstab</filename>:</para>
<para>A label should now exist in <filename
class="directory">/dev/ufs</filename> which may be added
to <filename>/etc/fstab</filename>:</para>
<programlisting>/dev/ufs/home /home ufs rw 2 2</programlisting>
@ -1147,7 +1126,7 @@ ggate0
to run <command>tunefs</command>.</para>
</note>
<para>Now the file system may be mounted like normal:</para>
<para>Now the file system may be mounted:</para>
<screen>&prompt.root; <userinput>mount /home</userinput></screen>
@ -1160,8 +1139,8 @@ ggate0
<para>File systems may also be created with a default label
by using the <option>-L</option> flag with
<command>newfs</command>. See the &man.newfs.8; manual page
for more information.</para>
<command>newfs</command>. Refer to &man.newfs.8; for
more information.</para>
<para>The following command can be used to destroy the
label:</para>
@ -1185,7 +1164,7 @@ ggate0
<filename class="directory">/</filename>,
<filename class="directory">/var</filename>,
<filename class="directory">/usr</filename> and
<filename class="directory">/tmp</filename> file systems, as
<filename class="directory">/tmp</filename>, as
well as a swap partition.</para>
<para>Reboot the system, and at the &man.loader.8; prompt,
@ -1207,8 +1186,8 @@ GEOM_LABEL: Label for provider /dev/ad0s1b is label/swap
<para>The system will continue with multi-user boot. After
the boot completes, edit <filename>/etc/fstab</filename> and
replace the conventional device names, with their respective
labels. The final <filename>/etc/fstab</filename> file will
look like the following:</para>
labels. The final <filename>/etc/fstab</filename> will
look like this:</para>
<programlisting># Device Mountpoint FStype Options Dump Pass#
/dev/label/swap none swap sw 0 0
@ -1232,24 +1211,23 @@ devfs on /dev (devfs, local)
<para>Starting with &os;&nbsp;7.2, the &man.glabel.8; class
supports a new label type for <acronym>UFS</acronym> file
systems, based on the unique file system id,
<literal>ufsid</literal>. These labels may be found in the
<filename class="directory">/dev/ufsid</filename> directory
and are created automatically during system startup. It is
possible to use <literal>ufsid</literal> labels to mount
partitions using the <filename>/etc/fstab</filename> facility.
Use the <command>glabel status</command> command to receive a
list of file systems and their corresponding
<literal>ufsid</literal> labels:</para>
<literal>ufsid</literal>. These labels may be found in
<filename class="directory">/dev/ufsid</filename> and are
created automatically during system startup. It is possible
to use <literal>ufsid</literal> labels to mount partitions
using <filename>/etc/fstab</filename>. Use <command>glabel
status</command> to receive a list of file systems and their
corresponding <literal>ufsid</literal> labels:</para>
<screen>&prompt.user; <userinput>glabel status</userinput>
Name Status Components
ufsid/486b6fc38d330916 N/A ad4s1d
ufsid/486b6fc16926168e N/A ad4s1f</screen>
<para>In the above example <devicename>ad4s1d</devicename>
represents the <filename class="directory">/var</filename>
file system, while <devicename>ad4s1f</devicename> represents
the <filename class="directory">/usr</filename> file system.
<para>In the above example, <devicename>ad4s1d</devicename>
represents <filename class="directory">/var</filename>,
while <devicename>ad4s1f</devicename> represents
<filename class="directory">/usr</filename>.
Using the <literal>ufsid</literal> values shown, these
partitions may now be mounted with the following entries in
<filename>/etc/fstab</filename>:</para>
@ -1258,9 +1236,9 @@ ufsid/486b6fc16926168e N/A ad4s1f</screen>
/dev/ufsid/486b6fc16926168e /usr ufs rw 2 2</programlisting>
<para>Any partitions with <literal>ufsid</literal> labels can be
mounted in this way, eliminating the need to create permanent
labels for them manually, while still enjoying the benefits of
device-name independent mounting.</para>
mounted in this way, eliminating the need to manually create
permanent labels, while still enjoying the benefits of device
name independent mounting.</para>
</sect2>
</sect1>
@ -1274,51 +1252,50 @@ ufsid/486b6fc16926168e N/A ad4s1f</screen>
<primary>Journaling</primary>
</indexterm>
<para>With the release of &os; 7.0, the long awaited feature
of journals has been implemented. The implementation itself is
provided through the <acronym>GEOM</acronym> subsystem and is
easily configured via the &man.gjournal.8; utility.</para>
<para>Beginning with &os;&nbsp;7.0, support for UFS journals is
available. The implementation is provided through the
<acronym>GEOM</acronym> subsystem and is configured using
&man.gjournal.8;.</para>
<para>What is journaling? Journaling capability stores a log of
file system transactions, i.e.: changes that make up a complete
disk write operation, before meta-data and file writes are
committed to the disk proper. This transaction log can later
be replayed to redo file system transactions, preventing file
system inconsistencies.</para>
<para>Journaling stores a log of file system transactions, such as
changes that make up a complete disk write operation, before
meta-data and file writes are committed to the disk. This
transaction log can later be replayed to redo file system
transactions, preventing file system inconsistencies.</para>
<para>This method is yet another mechanism to protect against data
loss and inconsistencies of the file system. Unlike Soft
Updates which tracks and enforces meta-data updates and
Snapshots which is an image of the file system, an actual log is
stored in disk space specifically reserved for this task, and in
some cases may be stored on another disk entirely.</para>
<para>This method provides another mechanism to protect against
data loss and inconsistencies of the file system. Unlike Soft
Updates, which tracks and enforces meta-data updates, and
snapshots, which create an image of the file system, a log is
stored in disk space specifically for this task, and in
some cases, may be stored on another disk entirely.</para>
<para>Unlike other file system journaling implementations, the
<command>gjournal</command> method is block based and not
implemented as part of the file system - only as a
implemented as part of the file system. It is a
<acronym>GEOM</acronym> extension.</para>
<para>To enable support for <command>gjournal</command>, the
&os; kernel must have the following option - which is the
default on &os; 7.0 and later systems:</para>
&os; kernel must have the following option which is the
default on &os;&nbsp;7.0 and later:</para>
<programlisting>options UFS_GJOURNAL</programlisting>
<para>If journaled volumes need to be mounted during startup, the
<filename>geom_journal.ko</filename> kernel module will also
have to be loaded, by adding the following line in
<filename>geom_journal.ko</filename> kernel module needs to be
loaded, by adding the following line to
<filename>/boot/loader.conf</filename>:</para>
<programlisting>geom_journal_load="YES"</programlisting>
<para>Alternatively, this function can also be built into a custom
<para>Alternatively, this function can be built into a custom
kernel, by adding the following line in the kernel configuration
file:</para>
<programlisting>options GEOM_JOURNAL</programlisting>
<para>Creating a journal on a free file system may now be done
using the following steps, considering that the
using the following steps. In this example,
<devicename>da4</devicename> is a new <acronym>SCSI</acronym>
disk:</para>
@ -1332,12 +1309,11 @@ ufsid/486b6fc16926168e N/A ad4s1f</screen>
<screen>&prompt.root; <userinput>newfs -O 2 -J /dev/da4.journal</userinput></screen>
<para>The previously issued command will create a
<acronym>UFS</acronym>2 file system on the journaled
device.</para>
<para>This command will creates a <acronym>UFS</acronym>2 file
system on the journaled device.</para>
<para>Effectively <command>mount</command> the device at the
desired point with:</para>
<para><command>mount</command> the device at the desired point
with:</para>
<screen>&prompt.root; <userinput>mount /dev/da4.journal <replaceable>/mnt</replaceable></userinput></screen>
@ -1351,21 +1327,21 @@ ufsid/486b6fc16926168e N/A ad4s1f</screen>
<devicename>ad4s2.journal</devicename>.</para>
</note>
<para>For better performance, keeping the journal on another disk
may be desired. For these cases, the journal provider or
storage device should be listed after the device to enable
journaling on. Journaling may also be enabled on current file
systems by using <command>tunefs</command>; however, always make
a backup before attempting to alter a file system. In most
cases, the <command>gjournal</command> will fail if it is unable
to create the actual journal but this does not protect against
data loss incurred as a result of misusing
<para>For better performance, the journal may be kept on another
disk. In this configuration, the journal provider or storage
device should be listed after the device to enable journaling
on. Journaling may also be enabled on current file systems by
using <command>tunefs</command>. However,
<emphasis>always</emphasis> make a backup before attempting to
alter a file system. In most cases, <command>gjournal</command>
will fail if it is unable to create the journal, but this does
not protect against data loss incurred as a result of misusing
<command>tunefs</command>.</para>
<para>It is also possible to journal the boot disk of a &os;
system. Please refer to the article <ulink
system. Refer to the article <ulink
url="&url.articles.gjournal-desktop;">Implementing UFS
Journaling on a Desktop PC</ulink> for detailed instructions
on this task.</para>
Journaling on a Desktop PC</ulink> for detailed
instructions.</para>
</sect1>
</chapter>