svn commit: r43698 - head/en_US.ISO8859-1/books/handbook/disks
Dru Lavigne
dru at FreeBSD.org
Thu Jan 30 21:06:20 UTC 2014
Author: dru
Date: Thu Jan 30 21:06:20 2014
New Revision: 43698
URL: http://svnweb.freebsd.org/changeset/doc/43698
Log:
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
Modified:
head/en_US.ISO8859-1/books/handbook/disks/chapter.xml
Modified: head/en_US.ISO8859-1/books/handbook/disks/chapter.xml
==============================================================================
--- head/en_US.ISO8859-1/books/handbook/disks/chapter.xml Thu Jan 30 19:00:09 2014 (r43697)
+++ head/en_US.ISO8859-1/books/handbook/disks/chapter.xml Thu Jan 30 21:06:20 2014 (r43698)
@@ -1123,12 +1123,12 @@ cd0: Attempt to query device size failed
<note>
<para>In order to support working files larger than 4.38GB, an
- UDF/ISO-9660 hybrid filesystem must be created by passing
+ UDF/ISO-9660 hybrid file system must be created by passing
<option>-udf -iso-level 3</option> to &man.mkisofs.8; and
all related programs, such as &man.growisofs.1;. This is
required only when creating an ISO image file or when
writing files directly to a disk. Since a disk created this
- way must be mounted as an UDF filesystem with
+ way must be mounted as an UDF file system with
&man.mount.udf.8;, it will be usable only on an UDF aware
operating system. Otherwise it will look as if it contains
corrupted files.</para>
@@ -1610,7 +1610,7 @@ cd0: Attempt to query device size failed
</listitem>
<listitem>
- <para>Filesystem snapshots, which are useful for restoring
+ <para>File system snapshots, which are useful for restoring
deleted files or previous versions of files.</para>
</listitem>
@@ -1650,24 +1650,20 @@ cd0: Attempt to query device size failed
<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. Unlike other backup software,
- <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,
- but rather writes the raw data blocks that comprise files and
- directories. When used to extract data,
- <command>restore</command> stores temporary files in
- <filename>/tmp/</filename> by default. When using a recovery
- disk with a small <filename>/tmp</filename>, set
- <envar>TMPDIR</envar> to a directory with more free space in
- order for the restore to succeed.</para>
+ <para>The traditional &unix; programs for backing up a file
+ system are &man.dump.8;, which creates the backup, and
+ &man.restore.8;, which restores the backup. These utilities
+ work at the disk block level, below the
+ abstractions of the files, links, and directories that are created
+ by file systems. Unlike other backup software,
+ <command>dump</command> backs up an entire file system and
+ is unable to backup only part of a file system or
+ a directory tree that spans multiple file systems.
+ Instead of writing files and directories, <command>dump</command>
+ writes the raw data blocks that comprise files and
+ directories.</para>
- <note>
+ <note>
<para>If <command>dump</command> is used on the root
directory, it will not back up <filename>/home</filename>,
<filename>/usr</filename> or many other
@@ -1675,39 +1671,34 @@ cd0: Attempt to query device size failed
file systems or symbolic links into those file
systems.</para>
</note>
+
+ <para>When used to restore data,
+ <command>restore</command> stores temporary files in
+ <filename>/tmp/</filename> by default. When using a recovery
+ disk with a small <filename>/tmp</filename>, set
+ <envar>TMPDIR</envar> to a directory with more free space in
+ order for the restore to succeed.</para>
- <para><command>dump</command> has quirks that remain from its
+ <para>When using <command>dump</command>, be aware that some quirks remain from its
early days in Version 6 of AT&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>
+ default parameters assume a backup to a 9-track tape, rather than
+ to another media or the high-density tapes available today.
+ These defaults must be overridden on the command line.</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 &man.rcmd.3; and &man.ruserok.3; to
- access the remote tape drive. Therefore, the user performing
- the backup must be listed in <filename>.rhosts</filename> on
- the remote computer. The arguments to
- <command>rdump</command> and <command>rrestore</command> must
- be suitable to use on the remote computer. For example, to
- <command>rdump</command> from a &os; computer to an Exabyte
- tape drive connected to a host called
- <systemitem>komodo</systemitem>, use:</para>
-
- <screen>&prompt.root; <userinput>/sbin/rdump 0dsbfu 54000 13000 126 komodo:/dev/nsa8 /dev/da0a 2>&1</userinput></screen>
-
- <para>There are security implications to allowing
- <filename>.rhosts</filename> authentication, so use
- with caution.</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>
+ <para>It is possible to backup a file system across the network to a
+ another system or to a tape drive attached to another computer.
+ While the &man.rdump.8; and &man.rrestore.8; utilities can be
+ used for this purpose, they are not considered to be secure.</para>
+
+ <para>Instead, one can use <command>dump</command> and
+ <command>restore</command> in a more secure fashion over an
+ <acronym>SSH</acronym> connection. This example creates a
+ full, compressed backup of the <filename>/usr</filename> file
+ system and sends the backup file to the specified host over a
+ <acronym>SSH</acronym> connection.</para>
<example>
<title>Using <command>dump</command> over
@@ -1717,7 +1708,9 @@ cd0: Attempt to query device size failed
targetuser at targetmachine.example.com dd of=/mybigfiles/dump-usr-l0.gz</userinput></screen>
</example>
- <para>Or, use the built-in <envar>RSH</envar>:</para>
+ <para>This example sets <envar>RSH</envar> in order to write the
+ the backup to a tape drive on a remote system over a
+ <acronym>SSH</acronym> connection:</para>
<example>
<title>Using <command>dump</command> over
@@ -1738,60 +1731,73 @@ cd0: Attempt to query device size failed
<para>Several built-in utilities are available for backing up
and restoring specified files and directories as needed.</para>
-
- <para>&man.tar.1; also dates back to Version 6 of AT&T
- &unix;, circa 1975. <command>tar</command> operates in
- cooperation with the file system and 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 it does not require the unusual command
- pipeline that <command>cpio</command> uses.</para>
+
+ <para>A good choice for making a backup of all of the files in a
+ directory is &man.tar.1;. This utility dates back to Version 6 of AT&T
+ &unix; and by default assumes a recursive backup to a local tape
+ device. Switches can be used to instead specify the name of
+ a backup file.</para>
<indexterm><primary><command>tar</command></primary></indexterm>
- <para>To <command>tar</command> to an Exabyte tape drive
- connected to a host called
- <systemitem>komodo</systemitem>:</para>
+ <para>This example creates a compressed backup of the current
+ directory and saves it to
+ <filename>/tmp/mybackup.tgz</filename>. When creating a
+ backup file, make sure that the backup is not saved to the
+ same directory that is being backed up.</para>
+
+ <example>
+ <title>Backing Up the Current Directory With
+ <command>tar</command></title>
+
+ <screen>&prompt.root; <userinput>tar czvf /tmp/mybackup.tgz . </userinput></screen>
+ </example>
+
+ <para>To restore the entire backup, <command>cd</command> into
+ the directory to restore into and specify the name of the
+ backup. Note that this will overwrite any newer versions of
+ files in the restore directory. When in doubt, restore to a
+ temporary directory or specify the name of the file within the
+ backup to restore.</para>
+
+ <example>
+ <title>Restoring Up the Current Directory With
+ <command>tar</command></title>
- <screen>&prompt.root; <userinput>tar cf - . | rsh komodo dd of=tape-device obs=20b</userinput></screen>
+ <screen>&prompt.root; <userinput>tar xzvf /tmp/mybackup.tgz</userinput></screen>
+ </example>
- <para>When backing up over an insecure network, instead use
- <command>ssh</command>.</para>
+ <para>There are dozens of available switches which are described
+ in &man.tar.1;. This utility also supports the use of exclude
+ patterns to specify which files should not be included when
+ backing up the specified directory or restoring files from a
+ backup.</para>
<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> includes
- options 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>Since <command>cpio</command> does not support backups
- across the network, use a pipeline and <command>ssh</command>
- to send the data to a remote tape drive.</para>
-
- <screen>&prompt.root; <userinput>for f in directory_list; do</userinput>
-<userinput>find $f >> backup.list</userinput>
-<userinput>done</userinput>
-&prompt.root; <userinput>cpio -v -o --format=newc < backup.list | ssh user at host "cat > backup_device"</userinput></screen>
-
- <para>Where <replaceable>directory_list</replaceable> is the
- list of directories 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, such as
- <filename>/dev/nsa0</filename>).</para>
+ <para>To create a backup using a specified list of files and
+ directories, &man.cpio.1; is a good choice. Unlike
+ <command>tar</command>,
+ <command>cpio</command> does not know
+ how to walk the directory tree and it must be provided the list of files
+ to backup.</para>
+
+ <para>For example, a list of files can be created using
+ <command>ls</command> or <command>find</command>. This example
+ creates a recursive listing of the current directory which is
+ then piped to <command>cpio</command> in order to create an
+ output backup file named
+ <filename>/tmp/mybackup.cpio</filename>.</para>
+
+ <example>
+ <title>Using<command>ls</command> and <command>cpio</command>
+ to Make a Recursive Backup of the Current Directory</title>
+
+ <screen>&prompt.root; <userinput>ls -R | cpio -ovF /tmp/mybackup.cpio</userinput></screen>
+ </example>
<indexterm>
<primary>backup software</primary>
@@ -1801,16 +1807,24 @@ cd0: Attempt to query device size failed
<indexterm><primary>POSIX</primary></indexterm>
<indexterm><primary>IEEE</primary></indexterm>
- <para>&man.pax.1; is the IEEE/&posix; answer to
- <command>tar</command> and <command>cpio</command>. Over the
- years the various versions of <command>tar</command> and
- <command>cpio</command> have become slightly incompatible. So
- rather than fight it out to fully standardize them, &posix;
- created a new archive utility. <command>pax</command>
+ <para>A backup utility which tries to bridge the features provided by
+ <command>tar</command> and <command>cpio</command> is &man.pax.1;. Over the
+ years, the various versions of <command>tar</command> and
+ <command>cpio</command> became slightly incompatible. &posix;
+ created <command>pax</command> which
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>
+ plus new formats of its own.</para>
+
+ <para>The <command>pax</command> equivalent to the previous
+ examples would be:</para>
+
+ <example>
+ <title>Backing Up the Current Directory With
+ <command>pax</command></title>
+
+ <screen>&prompt.root; <userinput>pax -wf /tmp/mybackup.pax .</userinput></screen>
+ </example>
</sect2>
<sect2 xml:id="backups-programs-amanda">
@@ -1929,7 +1943,7 @@ cd0: Attempt to query device size failed
Select the correct country, then choose
<guimenuitem>Fixit -- Repair mode with CD-ROM/DVD/floppy or
start a shell.</guimenuitem> then select
- <guimenuitem>CD-ROM/DVD -- Use the live filesystem
+ <guimenuitem>CD-ROM/DVD -- Use the live file system
CD-ROM/DVD</guimenuitem>.
<command>restore</command> and the other needed programs
are located in <filename>/mnt2/rescue</filename>.</para>
@@ -3588,13 +3602,13 @@ Device 1K-blocks Used Av
reports 0 bytes of <literal>dirty</literal> extents.</para>
- <para>The next step is to create a filesystem on the
+ <para>The next step is to create a file system on the
<filename>/dev/hast/test</filename>
GEOM provider and mount it. This must be done on the
<literal>primary</literal> node, as
<filename>/dev/hast/test</filename>
appears only on the <literal>primary</literal> node. Creating
- the filesystem can take a few minutes, depending on the size
+ the file system can take a few minutes, depending on the size
of the hard drive:</para>
<screen>&prompt.root; <userinput>newfs -U /dev/hast/test</userinput>
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