Next pass through this chapter.
Clarified text in File System Backups Redid examples in Directory Backups to show how 3 utils differ when creating similar backups. New examples are aimed at what a new user is likely to do. More complex examples should be added. Next pass will finish this section, to be followed by white space fix-ups. Sponsored by: iXsystems
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Dru Lavigne
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2020-12-08 03:00:23 +00:00
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1 changed files with 113 additions and 99 deletions
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@ -1123,12 +1123,12 @@ cd0: Attempt to query device size failed: NOT READY, Medium not present - tray c
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<note>
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<para>In order to support working files larger than 4.38GB, an
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UDF/ISO-9660 hybrid filesystem must be created by passing
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UDF/ISO-9660 hybrid file system must be created by passing
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<option>-udf -iso-level 3</option> to &man.mkisofs.8; and
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all related programs, such as &man.growisofs.1;. This is
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required only when creating an ISO image file or when
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writing files directly to a disk. Since a disk created this
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way must be mounted as an UDF filesystem with
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way must be mounted as an UDF file system with
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&man.mount.udf.8;, it will be usable only on an UDF aware
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operating system. Otherwise it will look as if it contains
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corrupted files.</para>
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</listitem>
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<listitem>
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<para>Filesystem snapshots, which are useful for restoring
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<para>File system snapshots, which are useful for restoring
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deleted files or previous versions of files.</para>
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</listitem>
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@ -1650,24 +1650,20 @@ cd0: Attempt to query device size failed: NOT READY, Medium not present - tray c
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<primary><command>restore</command></primary>
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</indexterm>
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<para>The traditional &unix; backup programs are
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<command>dump</command> and <command>restore</command>. They
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operate on the drive as a collection of disk blocks, below the
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abstractions of files, links and directories that are created
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by the file systems. Unlike other backup software,
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<command>dump</command> backs up an entire file system on a
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device. It is unable to backup only part of a file system or
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a directory tree that spans more than one file system.
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<command>dump</command> does not write files and directories,
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but rather writes the raw data blocks that comprise files and
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directories. When used to extract data,
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<command>restore</command> stores temporary files in
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<filename>/tmp/</filename> by default. When using a recovery
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disk with a small <filename>/tmp</filename>, set
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<envar>TMPDIR</envar> to a directory with more free space in
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order for the restore to succeed.</para>
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<para>The traditional &unix; programs for backing up a file
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system are &man.dump.8;, which creates the backup, and
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&man.restore.8;, which restores the backup. These utilities
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work at the disk block level, below the
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abstractions of the files, links, and directories that are created
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by file systems. Unlike other backup software,
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<command>dump</command> backs up an entire file system and
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is unable to backup only part of a file system or
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a directory tree that spans multiple file systems.
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Instead of writing files and directories, <command>dump</command>
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writes the raw data blocks that comprise files and
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directories.</para>
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<note>
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<note>
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<para>If <command>dump</command> is used on the root
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directory, it will not back up <filename>/home</filename>,
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<filename>/usr</filename> or many other
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file systems or symbolic links into those file
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systems.</para>
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</note>
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<para>When used to restore data,
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<command>restore</command> stores temporary files in
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<filename>/tmp/</filename> by default. When using a recovery
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disk with a small <filename>/tmp</filename>, set
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<envar>TMPDIR</envar> to a directory with more free space in
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order for the restore to succeed.</para>
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<para><command>dump</command> has quirks that remain from its
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<para>When using <command>dump</command>, be aware that some quirks remain from its
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early days in Version 6 of AT&T &unix;,circa 1975. The
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default parameters are suitable for 9-track tapes (6250 bpi),
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not the high-density media available today (up to 62,182
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ftpi). These defaults must be overridden on the command line
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to utilize the capacity of current tape drives.</para>
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default parameters assume a backup to a 9-track tape, rather than
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to another media or the high-density tapes available today.
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These defaults must be overridden on the command line.</para>
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<indexterm>
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<primary><filename>.rhosts</filename></primary>
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</indexterm>
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<para>It is also possible to backup data across the network to a
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tape drive attached to another computer with
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<command>rdump</command> and <command>rrestore</command>.
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Both programs rely upon &man.rcmd.3; and &man.ruserok.3; to
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access the remote tape drive. Therefore, the user performing
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the backup must be listed in <filename>.rhosts</filename> on
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the remote computer. The arguments to
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<command>rdump</command> and <command>rrestore</command> must
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be suitable to use on the remote computer. For example, to
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<command>rdump</command> from a &os; computer to an Exabyte
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tape drive connected to a host called
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<systemitem>komodo</systemitem>, use:</para>
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<para>It is possible to backup a file system across the network to a
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another system or to a tape drive attached to another computer.
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While the &man.rdump.8; and &man.rrestore.8; utilities can be
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used for this purpose, they are not considered to be secure.</para>
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<screen>&prompt.root; <userinput>/sbin/rdump 0dsbfu 54000 13000 126 komodo:/dev/nsa8 /dev/da0a 2>&1</userinput></screen>
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<para>There are security implications to allowing
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<filename>.rhosts</filename> authentication, so use
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with caution.</para>
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<para>It is also possible to use <command>dump</command> and
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<command>restore</command> in a more secure fashion over
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<command>ssh</command>.</para>
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<para>Instead, one can use <command>dump</command> and
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<command>restore</command> in a more secure fashion over an
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<acronym>SSH</acronym> connection. This example creates a
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full, compressed backup of the <filename>/usr</filename> file
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system and sends the backup file to the specified host over a
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<acronym>SSH</acronym> connection.</para>
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<example>
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<title>Using <command>dump</command> over
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targetuser@targetmachine.example.com dd of=/mybigfiles/dump-usr-l0.gz</userinput></screen>
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</example>
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<para>Or, use the built-in <envar>RSH</envar>:</para>
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<para>This example sets <envar>RSH</envar> in order to write the
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the backup to a tape drive on a remote system over a
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<acronym>SSH</acronym> connection:</para>
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<example>
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<title>Using <command>dump</command> over
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<para>Several built-in utilities are available for backing up
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and restoring specified files and directories as needed.</para>
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<para>&man.tar.1; also dates back to Version 6 of AT&T
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&unix;, circa 1975. <command>tar</command> operates in
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cooperation with the file system and writes files and
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directories to tape. <command>tar</command> does not support
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the full range of options that are available from
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&man.cpio.1;, but it does not require the unusual command
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pipeline that <command>cpio</command> uses.</para>
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<para>A good choice for making a backup of all of the files in a
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directory is &man.tar.1;. This utility dates back to Version 6 of AT&T
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&unix; and by default assumes a recursive backup to a local tape
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device. Switches can be used to instead specify the name of
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a backup file.</para>
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<indexterm><primary><command>tar</command></primary></indexterm>
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<para>To <command>tar</command> to an Exabyte tape drive
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connected to a host called
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<systemitem>komodo</systemitem>:</para>
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<para>This example creates a compressed backup of the current
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directory and saves it to
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<filename>/tmp/mybackup.tgz</filename>. When creating a
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backup file, make sure that the backup is not saved to the
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same directory that is being backed up.</para>
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<screen>&prompt.root; <userinput>tar cf - . | rsh komodo dd of=tape-device obs=20b</userinput></screen>
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<example>
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<title>Backing Up the Current Directory With
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<command>tar</command></title>
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<screen>&prompt.root; <userinput>tar czvf /tmp/mybackup.tgz . </userinput></screen>
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</example>
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<para>When backing up over an insecure network, instead use
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<command>ssh</command>.</para>
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<para>To restore the entire backup, <command>cd</command> into
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the directory to restore into and specify the name of the
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backup. Note that this will overwrite any newer versions of
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files in the restore directory. When in doubt, restore to a
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temporary directory or specify the name of the file within the
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backup to restore.</para>
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<example>
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<title>Restoring Up the Current Directory With
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<command>tar</command></title>
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<screen>&prompt.root; <userinput>tar xzvf /tmp/mybackup.tgz</userinput></screen>
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</example>
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<para>There are dozens of available switches which are described
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in &man.tar.1;. This utility also supports the use of exclude
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patterns to specify which files should not be included when
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backing up the specified directory or restoring files from a
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backup.</para>
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<indexterm>
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<primary>backup software</primary>
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<secondary><command>cpio</command></secondary>
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</indexterm>
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<para>&man.cpio.1; is the original &unix; file interchange tape
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program for magnetic media. <command>cpio</command> includes
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options to perform byte-swapping, write a number of different
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archive formats, and pipe the data to other programs. This
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last feature makes <command>cpio</command> an excellent choice
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for installation media. <command>cpio</command> does not know
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how to walk the directory tree and a list of files must be
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provided through <filename>stdin</filename>.</para>
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<para>To create a backup using a specified list of files and
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directories, &man.cpio.1; is a good choice. Unlike
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<command>tar</command>,
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<command>cpio</command> does not know
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how to walk the directory tree and it must be provided the list of files
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to backup.</para>
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<indexterm>
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<primary><command>cpio</command></primary>
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</indexterm>
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<para>For example, a list of files can be created using
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<command>ls</command> or <command>find</command>. This example
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creates a recursive listing of the current directory which is
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then piped to <command>cpio</command> in order to create an
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output backup file named
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<filename>/tmp/mybackup.cpio</filename>.</para>
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<para>Since <command>cpio</command> does not support backups
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across the network, use a pipeline and <command>ssh</command>
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to send the data to a remote tape drive.</para>
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<screen>&prompt.root; <userinput>for f in directory_list; do</userinput>
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<userinput>find $f >> backup.list</userinput>
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<userinput>done</userinput>
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&prompt.root; <userinput>cpio -v -o --format=newc < backup.list | ssh user@host "cat > backup_device"</userinput></screen>
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<para>Where <replaceable>directory_list</replaceable> is the
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list of directories to back up,
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<replaceable>user</replaceable>@<replaceable>host</replaceable>
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is the user/hostname combination that will be performing the
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backups, and <replaceable>backup_device</replaceable> is where
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the backups should be written to, such as
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<filename>/dev/nsa0</filename>).</para>
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<example>
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<title>Using<command>ls</command> and <command>cpio</command>
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to Make a Recursive Backup of the Current Directory</title>
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<screen>&prompt.root; <userinput>ls -R | cpio -ovF /tmp/mybackup.cpio</userinput></screen>
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</example>
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<indexterm>
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<primary>backup software</primary>
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<indexterm><primary>POSIX</primary></indexterm>
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<indexterm><primary>IEEE</primary></indexterm>
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<para>&man.pax.1; is the IEEE/&posix; answer to
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<command>tar</command> and <command>cpio</command>. Over the
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years the various versions of <command>tar</command> and
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<command>cpio</command> have become slightly incompatible. So
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rather than fight it out to fully standardize them, &posix;
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created a new archive utility. <command>pax</command>
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<para>A backup utility which tries to bridge the features provided by
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<command>tar</command> and <command>cpio</command> is &man.pax.1;. Over the
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years, the various versions of <command>tar</command> and
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<command>cpio</command> became slightly incompatible. &posix;
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created <command>pax</command> which
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attempts to read and write many of the various
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<command>cpio</command> and <command>tar</command> formats,
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plus new formats of its own. Its command set more resembles
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<command>cpio</command> than <command>tar</command>.</para>
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plus new formats of its own.</para>
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<para>The <command>pax</command> equivalent to the previous
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examples would be:</para>
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<example>
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<title>Backing Up the Current Directory With
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<command>pax</command></title>
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<screen>&prompt.root; <userinput>pax -wf /tmp/mybackup.pax .</userinput></screen>
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</example>
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</sect2>
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<sect2 xml:id="backups-programs-amanda">
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Select the correct country, then choose
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<guimenuitem>Fixit -- Repair mode with CD-ROM/DVD/floppy or
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start a shell.</guimenuitem> then select
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<guimenuitem>CD-ROM/DVD -- Use the live filesystem
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<guimenuitem>CD-ROM/DVD -- Use the live file system
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CD-ROM/DVD</guimenuitem>.
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<command>restore</command> and the other needed programs
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are located in <filename>/mnt2/rescue</filename>.</para>
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@ -3588,13 +3602,13 @@ Device 1K-blocks Used Avail Capacity
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reports 0 bytes of <literal>dirty</literal> extents.</para>
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<para>The next step is to create a filesystem on the
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<para>The next step is to create a file system on the
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<filename>/dev/hast/test</filename>
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GEOM provider and mount it. This must be done on the
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<literal>primary</literal> node, as
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<filename>/dev/hast/test</filename>
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appears only on the <literal>primary</literal> node. Creating
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the filesystem can take a few minutes, depending on the size
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the file system can take a few minutes, depending on the size
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of the hard drive:</para>
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<screen>&prompt.root; <userinput>newfs -U /dev/hast/test</userinput>
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