trunk/system-administrator/backup.sgml

<!-- Debian System Administrator's Manual - Backup and Restore -->

    <chapt id="sysadmin-backup">

      <heading>Backup and Restore</heading>

      <p>
        author = Tapio Lehtonen 
      </p>

      <p>
        topics = why backup, what to backup, how to backup, backup
        devices and media </p

      <sect>
<heading>Why backup?</heading>
<p>Backups are needed in case a file or a group of files is lost. The
      reasons for losing files include
<list>
<item>Hardware failure like disk breaking,
<item>computer being stolen and
<item>accidentally deleting wrong file.
</list>
</p>

<p>Backups help in all the above situations. In addition, it may be
good to have access to older versions of files, for example a
configuration file worked a week ago, but since then it has been
changed and nobody remembers how, its just not working anymore.
</p>

<p>There are other solutions, and they are good to have if you can
afford them. These include
<list>
<item>redundant disks (RAID 1 or 5), so that one disk can break
without loss of data,
<item>locking up computers,
<item>using an undelete system (or not making mistakes when deleting
files :-)
</list>
These help, but if there is anything you do not want to lose on the
computer, <strong>make sure there are backups and they can be
restored.</strong>

      </sect>

      <sect>
<heading>What to backup?</heading> 

<p>If there is room on the backup media, and time limits permit
running backups long enough, it probably is wisest to back up
everything. You may skip <prgn>/tmp</prgn> or other places where it is
known there are only temporary files that nobody wants to
backup. </p>

<p>If space or time limits place restrictions, consider not backing up
the following:
<list>
<item>Files that come directly from a CD or other removable media. It
may even be faster to copy them again from CD than restoring from
backup media. 
<item>Files that can be regenerated easily. For example, object files
that can be made with <prgn>make</prgn>. Just make sure all the source
files and compilers are backed up. 
<item>If the Internet connection is fast, it may be easy enough to
download files again. Just keep a list of the files and where to
download them from. 
</list></p>

<p> </p>


      </sect>

      <sect>
<heading>Backup devices and media</heading>

<p>Meta: Floppy (tar gz /etc), zip-drive and LS-120
CD-R and CD-RW, floppy tape, SCSI tape, hardware compression</p>

<p>You need some media to store the backups. It is preferable to use
removable media, to store the backups away from the computer and to
get "unlimited" storage for backups. </p>

<p>If the backups are on-line, they can be wiped out by mistake. If
the backups are on the same disk as the original data, they do not
help at all if the disk fails and is not readable anymore. If the
backup media is cheap, it is possible to take a backup every day and
store them indefinitely. </p>

<sect1>
<heading>Floppy</heading

<p>Floppy disks are cheap, and on PC computers there usually is a
floppy disk drive. On the other hand, it is not very fast to write to
a floppy, and the capacity of 1.4MBytes is not very much. If the
backup does not fit on one media, taking backups becomes an arduous
task, what with having to stand by and change the media every now and
then. </p>

<p>However, if the data to be backed up fits in one floppy, they are a
reasonable alternative. Compressing the data usually means it uses
about 50% of the original size. Thus, you can expect to get almost
3MBytes to one 1.4M floppy disk with compression. </p>

<p>There are different ways to use the floppy with tar:
<list>
<item>write directly to the device <prgn>/dev/fd0</prgn>,
<item>use the floppy with DOS file system, and copy the tar file there
with <prgn>mcopy</prgn> (see info file mtools with command <prgn>info
mtools</prgn>) and 
<item>Create a Linux filesystem on the floppy, mount, write like to
any Linux disk and unmount the floppy.
</list>

<p>Here is an example to backup the <prgn>/etc</prgn> directory tree
to floppy. First check how large the directory tree is:
<example>
dilbert# du --summarize --kilobytes /etc
2515    /etc
dilbert# 
</example>
This shows 2.5MBytes, so it should fit on one floppy if the data is
compressed. </p>

<p>The first example below uses the floppy as removable media with Linux filesystem. </p>

<p>Now an EXT2 filesystem is created on the floppy. This is the
filesystem Linux uses on hard disk partitions, but it is possible to
format all disk media to EXT2. Note, that all data on the media is
lost when it is formatted. The first floppy drive is device
<prgn>/dev/fd0</prgn>.  
<example>
dilbert# mkfs -t ext2 /dev/fd0 1440
mke2fs 1.12, 9-Jul-98 for EXT2 FS 0.5b, 95/08/09
Linux ext2 filesystem format
Filesystem label=
360 inodes, 1440 blocks
72 blocks (5.00%) reserved for the super user
First data block=1
Block size=1024 (log=0)
Fragment size=1024 (log=0)
1 block group
8192 blocks per group, 8192 fragments per group
360 inodes per group

Writing inode tables: done      1
Writing superblocks and filesystem accounting information: done
dilbert#
</example>
</p>

<p>Now the floppy disk is mounted and backup is run and tested. Note,
that the mount point <prng>/A</prgn> must already exist (see <manref
name="mount" sect="8">
<example>
dilbert# mount -t ext2 /dev/fd0 /A
dilbert# df -h
Filesystem            Size  Used  Avail  Capacity Mounted on
/dev/sda5              99M   14M    80M     15%   /
/dev/sda6             964M  540M   374M     59%   /usr
/dev/sda7             190M   32M   148M     18%   /var
/dev/sda8             2.7G  1.2G   1.4G     46%   /export
/dev/sdb2             3.8G  2.3G   1.4G     62%   /export2
dilbert:/export/home  2.7G  1.2G   1.4G     46%   /amd/dilbert/export/home
/dev/fd0              1.4M   13K   1.3M      1%   /A
dilbert# cd /
dilbert# tar czf /A/etc.tgz ./etc
dilbert# df -h
Filesystem            Size  Used  Avail  Capacity Mounted on
/dev/sda5              99M   14M    80M     15%   /
/dev/sda6             964M  540M   374M     59%   /usr
/dev/sda7             190M   32M   148M     18%   /var
/dev/sda8             2.7G  1.2G   1.4G     46%   /export
/dev/sdb2             3.8G  2.3G   1.4G     62%   /export2
dilbert:/export/home  2.7G  1.2G   1.4G     46%   /amd/dilbert/export/home
/dev/fd0              1.4M  483K   835K     37%   /A
dilbert# ls -l /A
total 482
-rw-r--r--   1 root     root       477376 Nov 12 22:15 etc.tgz
drwxr-xr-x   2 root     root        12288 Nov 12 21:54 lost+found
dilbert#

</example>
</p>

<p>Here we change working directory to <prgn>/tmp</prgn>, and restore
the backup to <prgn>/tmp/etc</prgn>. 
<example>
dilbert# cd /tmp
dilbert# ls -l 
total 252
-r--r--r--   1 tale     tale        98774 Nov  9 23:01 Packages
drwxr-xr-x   6 tale     tale         1024 Nov  8 21:13 nscomm40-tale
-rw-------   1 tale     tale       153107 Nov 10 23:51 nsmail3648B5740C333F2
drwx------   2 tale     tale         1024 Nov  8 20:51 orbit-tale
drwx------   2 vieras   vieras       1024 Nov  7 17:52 orbit-vieras
dilbert# tar xzf /A/etc.tgz 
dilbert# ls -l
total 257
-r--r--r--   1 tale     tale        98774 Nov  9 23:01 Packages
drwxr-xr-x  59 root     root         5120 Nov 12 22:13 etc
drwxr-xr-x   6 tale     tale         1024 Nov  8 21:13 nscomm40-tale
-rw-------   1 tale     tale       153107 Nov 10 23:51 nsmail3648B5740C333F2
drwx------   2 tale     tale         1024 Nov  8 20:51 orbit-tale
drwx------   2 vieras   vieras       1024 Nov  7 17:52 orbit-vieras
dilbert# du --summarize --kilobytes /tmp/etc
2509    /tmp/etc
dilbert# umount /A
dilbert#
</example>
</p>

<p>It looks like the backup is on the floppy and we could even read it
back. The last command in the previous example unmounts the
floppy. This is <strong>very important!</strong>. If you mount a
removable media, it <strong>must be unmounted</strong> before it is
removed from the drive. </p>

<p>As another example, we write the backup directly to the
<prgn>/dev/fd0</prgn> device:
<example>
dilbert# cd /
dilbert# tar czf /dev/fd0 ./etc
dilbert# tar tzf /dev/fd0 | head
./etc/
./etc/modules
./etc/xemacs/
./etc/xemacs/site-start-19.d/
./etc/xemacs/site-start-19.d/50dpkg-dev.el
./etc/init.d/
./etc/init.d/network
./etc/init.d/modutils
./etc/init.d/kerneld
./etc/init.d/kdm
Broken pipe
dilbert#
</example>
</p>

<p>We could read the listing (option <prgn>t</prgn> for
<prgn>tar</prgn>) from the floppy, so we can assume the backup is
OK. Note, that if you plan to read this floppy back later,
<strong>make sure you remember how the floppy was written</strong>. If
you forget it was written with <prgn>tar</prgn> and with compression,
you spend a lot of time figuring it out. This same applies to all
media that you store for any longer period of time, and especially if
you send the media to someone else. </p>

<p>The above method is usable also with tape drives. Replace the
device name <prgn>/dev/fd0</prgn> with device name for the tape drive,
and you can use <prgn>tar</prgn> as Tape ARchiver. </p>

</sect1>

<sect1>
<heading>High Capacity Floppies</heading>

<p>High capacity floppies are 
<list>
<item><url id="http://www.iomega.com/product/zip" name="Iomega Zip-drive">, 
<item><url id="http://www.superdisk.com/" name="LS-120">, <url id="http://www.winstation.com/main.html"
name="LS-120">,
<item><url id="http://www.sony.com/HiFD" name="Sony HiFD">,
<item><url id="http://www.syquest.com/" name="SyQuest EZFlyer"> and 
<item><url id="SyQuest" name="SyQuest SparQ">
</list>
</p>

<p>All of these are about floppy disk size, store 100MBytes to
200MBytes (SparQ about 1.0GBytes) and are faster and more expensive
than floppy drives. They are connected to EIDE port, Parallel port,
SCSI or USB. LS-120 and Sony SuperFloppy can read and write ordinary
1.4MByte floppy disks.

<p>You can use these things like in the above examples where a floppy
disk was used, but you have to
install the devices and the device driver software before they can be
used. Then the device name depends on what kind of connection the
thing uses. </p>

<p>There is more info on using the above high capacity floppies on Linux in the
HOWTO documents. (reference to HOWTOs???)</p>


<p><strong>Somebody with experience from the above devices: please confirm my
guessing above or send info on how they can be used.</strong></p>

</sect1>

<sect1>
<heading>CD-R and CD-RW</heading>

<p>Meta: Capacity <= 640MBytes, speed 150 -- 600KBits/sek. Special software
needed to burn the CD. DVD-RAM</p>

<p>CD writers can be used as backup devices. Writable CD media is
either writable exactly once (CD-R), or erasable and rewritable
(CD-RW). CD-R disks can be read on ordinary CD drives, but CD-RW disks
need Multi-Read capability from the reader. This is good to know if
you plan to read the CD back on some other computer.</p>

<p>Assuming the CD writer is installed and configured correctly, and
you have the necessary software to write to the CD, taking backups is
best done with the first method in the floppy disk example above,
i.e. creating a Linux file system on the CD. Since the CD is a disk,
i.e. a random access device, using it this way is easy. Just mount it
and copy files or whole directory trees there.</p>

<p>Restoring is also straightforward, since the CD can be examined
with ordinary file system commands like <prgn>ls</prng>, and it is
easy to copy a single file back. You can also compare the files in the
backup to files in hard disk with <prgn>diff</prgn> for example. </p>

<p>Problems with CD-R are their write once -nature. They need to be
written all in one go, and then closed. After closing, it is not
possible to modify the CD, so if there is something wrong there it has
to be thrown away. </p>

<p>CD-RW can be erased, but my understanding is the whole disk must be
erased. In addition, looks like formatting a CD-RW takes about one
hour. </p>


</sect1>

<sect1>
<heading>Tapes</heading>

<p>Meta: Popular backup media. Wide range of speeds, capacities and cost. </p>

<p>Tape drives are popular backup devices. The media is relatively
cheap per gigabyte, and tape capacities go up to several tens of
gigabytes. On the other hand, the tape drives may be expensive and
write speeds slower than disks.</p>

<p></p>

<p></p>

<p></p>

<p></p>

<p></p>

</sect1>

      </sect>


      <sect>
<heading>Backup methods and software</heading>
<p>Backup methods include simply copying files to another media, using
dd, tar or similar program to create an archive and using special backup
programs. 

<sect1><heading>Network backups</heading>
<p>Meta: Enterprise environment, Legato Networker, HP Omniback, etc. Linux clients. 

<p>In an enterprise environment there may be a backup server running
some network backup software. If there are Linux clients available for
that software, its possible to install the Linux client, configure the
client machine on the backup server and start taking backups over the
LAN.</p>

<p>This is a low cost solution. If the backup server is already there,
Linux clients usually are free to download. Legato Networker and HP
Omniback have Linux clients available, but no technical support is
available from the vendor. 


<taglist compact>
<tag>Legato
<item><url id="http://www.legato.com/exchange/documents/NetWorker/CG-SW.html" name="Legato Networker">

<tag>HP Omniback
<item><url id="http://www.hp.com/openview/products/omniback.html" name="HP Omniback">
</taglist>
</p>
</sect1>

<sect1><heading>Tar et al</heading>
<p>Meta: Tar, dump, dd</p>

<p>Now for some examples. </p>

<p>In Debian GNU/Linux the <prgn>tar</prgn>
program is GNU tar, which has several extra features. Among them is
support for compressing the tar file while it is created. On the
average, compression squeezes the file to about 50% of the
uncompressed size. Your mileage may vary: files that are already
compressed, like *.zip and *.gif files do not compress at all, and
some file compress especially well, C source code files can go to 25%
of the uncompressed size.</p>

<p>Taking a compressed tar file from /export/home partition goes like
this:
<example>
cd /export
tar czf /tmp/home.tgz ./home
</example>
</p>

<p></p>

</sect1>


<sect1><heading>Backup software</heading>
<p>Meta: amanda, other backup software in Debian


</sect1>


      </sect>


      <sect>
<heading>Types of backup</heading>
<p>Meta: Full, incremental, differential, network, dump, level 0--9, </p>

<p>Meta: Check the backup can be restored, with original file owners and permissions.</p>

      </sect>

    </chapt>
      
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1	olly	670	<!-- Debian System Administrator's Manual - Backup and Restore -->
2
3			<chapt id="sysadmin-backup">
4
5			<heading>Backup and Restore</heading>
6
7			<p>
8	talehton	688	author = Tapio Lehtonen
9	olly	670	</p>
10
11			<p>
12	talehton	697	topics = why backup, what to backup, how to backup, backup
13			devices and media </p
14	olly	670
15			<sect>
16	talehton	688	<heading>Why backup?</heading>
17	talehton	708	<p>Backups are needed in case a file or a group of files is lost. The
18	talehton	697	reasons for losing files include
19			<list>
20			<item>Hardware failure like disk breaking,
21			<item>computer being stolen and
22			<item>accidentally deleting wrong file.
23			</list>
24			</p>
25
26	talehton	708	<p>Backups help in all the above situations. In addition, it may be
27			good to have access to older versions of files, for example a
28			configuration file worked a week ago, but since then it has been
29	talehton	697	changed and nobody remembers how, its just not working anymore.
30			</p>
31
32			<p>There are other solutions, and they are good to have if you can
33			afford them. These include
34			<list>
35			<item>redundant disks (RAID 1 or 5), so that one disk can break
36			without loss of data,
37			<item>locking up computers,
38			<item>using an undelete system (or not making mistakes when deleting
39			files :-)
40			</list>
41			These help, but if there is anything you do not want to lose on the
42			computer, <strong>make sure there are backups and they can be
43			restored.</strong>
44
45	talehton	688	</sect>
46
47			<sect>
48	talehton	697	<heading>What to backup?</heading>
49
50			<p>If there is room on the backup media, and time limits permit
51			running backups long enough, it probably is wisest to back up
52			everything. You may skip <prgn>/tmp</prgn> or other places where it is
53	talehton	708	known there are only temporary files that nobody wants to
54	talehton	697	backup. </p>
55
56	talehton	708	<p>If space or time limits place restrictions, consider not backing up
57	talehton	697	the following:
58			<list>
59			<item>Files that come directly from a CD or other removable media. It
60	talehton	729	may even be faster to copy them again from CD than restoring from
61	talehton	697	backup media.
62			<item>Files that can be regenerated easily. For example, object files
63			that can be made with <prgn>make</prgn>. Just make sure all the source
64			files and compilers are backed up.
65			<item>If the Internet connection is fast, it may be easy enough to
66			download files again. Just keep a list of the files and where to
67			download them from.
68			</list></p>
69
70			<p> </p>
71
72
73	talehton	688	</sect>
74
75			<sect>
76	talehton	708	<heading>Backup devices and media</heading>
77
78	talehton	725	<p>Meta: Floppy (tar gz /etc), zip-drive and LS-120
79	talehton	708	CD-R and CD-RW, floppy tape, SCSI tape, hardware compression</p>
80
81			<p>You need some media to store the backups. It is preferable to use
82			removable media, to store the backups away from the computer and to
83			get "unlimited" storage for backups. </p>
84
85			<p>If the backups are on-line, they can be wiped out by mistake. If
86			the backups are on the same disk as the original data, they do not
87			help at all if the disk fails and is not readable anymore. If the
88			backup media is cheap, it is possible to take a backup every day and
89			store them indefinitely. </p>
90
91			<sect1>
92			<heading>Floppy</heading
93
94			<p>Floppy disks are cheap, and on PC computers there usually is a
95			floppy disk drive. On the other hand, it is not very fast to write to
96	talehton	725	a floppy, and the capacity of 1.4MBytes is not very much. If the
97	talehton	708	backup does not fit on one media, taking backups becomes an arduous
98			task, what with having to stand by and change the media every now and
99			then. </p>
100
101			<p>However, if the data to be backed up fits in one floppy, they are a
102			reasonable alternative. Compressing the data usually means it uses
103			about 50% of the original size. Thus, you can expect to get almost
104			3MBytes to one 1.4M floppy disk with compression. </p>
105
106	talehton	725	<p>There are different ways to use the floppy with tar:
107			<list>
108			<item>write directly to the device <prgn>/dev/fd0</prgn>,
109			<item>use the floppy with DOS file system, and copy the tar file there
110			with <prgn>mcopy</prgn> (see info file mtools with command <prgn>info
111			mtools</prgn>) and
112			<item>Create a Linux filesystem on the floppy, mount, write like to
113			any Linux disk and unmount the floppy.
114			</list>
115
116	talehton	708	<p>Here is an example to backup the <prgn>/etc</prgn> directory tree
117			to floppy. First check how large the directory tree is:
118			<example>
119			dilbert# du --summarize --kilobytes /etc
120			2515 /etc
121			dilbert#
122			</example>
123			This shows 2.5MBytes, so it should fit on one floppy if the data is
124			compressed. </p>
125
126	talehton	725	<p>The first example below uses the floppy as removable media with Linux filesystem. </p>
127	talehton	708
128	talehton	729	<p>Now an EXT2 filesystem is created on the floppy. This is the
129	talehton	708	filesystem Linux uses on hard disk partitions, but it is possible to
130			format all disk media to EXT2. Note, that all data on the media is
131			lost when it is formatted. The first floppy drive is device
132			<prgn>/dev/fd0</prgn>.
133			<example>
134			dilbert# mkfs -t ext2 /dev/fd0 1440
135			mke2fs 1.12, 9-Jul-98 for EXT2 FS 0.5b, 95/08/09
136			Linux ext2 filesystem format
137			Filesystem label=
138			360 inodes, 1440 blocks
139			72 blocks (5.00%) reserved for the super user
140			First data block=1
141			Block size=1024 (log=0)
142			Fragment size=1024 (log=0)
143			1 block group
144			8192 blocks per group, 8192 fragments per group
145			360 inodes per group
146
147			Writing inode tables: done 1
148			Writing superblocks and filesystem accounting information: done
149			dilbert#
150			</example>
151			</p>
152
153	talehton	729	<p>Now the floppy disk is mounted and backup is run and tested. Note,
154			that the mount point <prng>/A</prgn> must already exist (see <manref
155			name="mount" sect="8">
156	talehton	708	<example>
157			dilbert# mount -t ext2 /dev/fd0 /A
158			dilbert# df -h
159			Filesystem Size Used Avail Capacity Mounted on
160			/dev/sda5 99M 14M 80M 15% /
161			/dev/sda6 964M 540M 374M 59% /usr
162			/dev/sda7 190M 32M 148M 18% /var
163			/dev/sda8 2.7G 1.2G 1.4G 46% /export
164			/dev/sdb2 3.8G 2.3G 1.4G 62% /export2
165			dilbert:/export/home 2.7G 1.2G 1.4G 46% /amd/dilbert/export/home
166			/dev/fd0 1.4M 13K 1.3M 1% /A
167			dilbert# cd /
168			dilbert# tar czf /A/etc.tgz ./etc
169			dilbert# df -h
170			Filesystem Size Used Avail Capacity Mounted on
171			/dev/sda5 99M 14M 80M 15% /
172			/dev/sda6 964M 540M 374M 59% /usr
173			/dev/sda7 190M 32M 148M 18% /var
174			/dev/sda8 2.7G 1.2G 1.4G 46% /export
175			/dev/sdb2 3.8G 2.3G 1.4G 62% /export2
176			dilbert:/export/home 2.7G 1.2G 1.4G 46% /amd/dilbert/export/home
177			/dev/fd0 1.4M 483K 835K 37% /A
178			dilbert# ls -l /A
179			total 482
180			-rw-r--r-- 1 root root 477376 Nov 12 22:15 etc.tgz
181			drwxr-xr-x 2 root root 12288 Nov 12 21:54 lost+found
182			dilbert#
183
184			</example>
185			</p>
186
187			<p>Here we change working directory to <prgn>/tmp</prgn>, and restore
188			the backup to <prgn>/tmp/etc</prgn>.
189			<example>
190			dilbert# cd /tmp
191			dilbert# ls -l
192			total 252
193			-r--r--r-- 1 tale tale 98774 Nov 9 23:01 Packages
194			drwxr-xr-x 6 tale tale 1024 Nov 8 21:13 nscomm40-tale
195			-rw------- 1 tale tale 153107 Nov 10 23:51 nsmail3648B5740C333F2
196			drwx------ 2 tale tale 1024 Nov 8 20:51 orbit-tale
197			drwx------ 2 vieras vieras 1024 Nov 7 17:52 orbit-vieras
198			dilbert# tar xzf /A/etc.tgz
199			dilbert# ls -l
200			total 257
201			-r--r--r-- 1 tale tale 98774 Nov 9 23:01 Packages
202			drwxr-xr-x 59 root root 5120 Nov 12 22:13 etc
203			drwxr-xr-x 6 tale tale 1024 Nov 8 21:13 nscomm40-tale
204			-rw------- 1 tale tale 153107 Nov 10 23:51 nsmail3648B5740C333F2
205			drwx------ 2 tale tale 1024 Nov 8 20:51 orbit-tale
206			drwx------ 2 vieras vieras 1024 Nov 7 17:52 orbit-vieras
207			dilbert# du --summarize --kilobytes /tmp/etc
208			2509 /tmp/etc
209			dilbert# umount /A
210			dilbert#
211			</example>
212			</p>
213
214			<p>It looks like the backup is on the floppy and we could even read it
215			back. The last command in the previous example unmounts the
216			floppy. This is <strong>very important!</strong>. If you mount a
217			removable media, it <strong>must be unmounted</strong> before it is
218			removed from the drive. </p>
219
220			<p>As another example, we write the backup directly to the
221			<prgn>/dev/fd0</prgn> device:
222			<example>
223			dilbert# cd /
224			dilbert# tar czf /dev/fd0 ./etc
225			dilbert# tar tzf /dev/fd0 \| head
226			./etc/
227			./etc/modules
228			./etc/xemacs/
229			./etc/xemacs/site-start-19.d/
230			./etc/xemacs/site-start-19.d/50dpkg-dev.el
231			./etc/init.d/
232			./etc/init.d/network
233			./etc/init.d/modutils
234			./etc/init.d/kerneld
235			./etc/init.d/kdm
236			Broken pipe
237			dilbert#
238			</example>
239			</p>
240
241			<p>We could read the listing (option <prgn>t</prgn> for
242			<prgn>tar</prgn>) from the floppy, so we can assume the backup is
243			OK. Note, that if you plan to read this floppy back later,
244			<strong>make sure you remember how the floppy was written</strong>. If
245			you forget it was written with <prgn>tar</prgn> and with compression,
246			you spend a lot of time figuring it out. This same applies to all
247			media that you store for any longer period of time, and especially if
248			you send the media to someone else. </p>
249
250			<p>The above method is usable also with tape drives. Replace the
251			device name <prgn>/dev/fd0</prgn> with device name for the tape drive,
252			and you can use <prgn>tar</prgn> as Tape ARchiver. </p>
253
254			</sect1>
255
256			<sect1>
257			<heading>High Capacity Floppies</heading>
258
259			<p>High capacity floppies are
260			<list>
261			<item><url id="http://www.iomega.com/product/zip" name="Iomega Zip-drive">,
262			<item><url id="http://www.superdisk.com/" name="LS-120">, <url id="http://www.winstation.com/main.html"
263	talehton	725	name="LS-120">,
264			<item><url id="http://www.sony.com/HiFD" name="Sony HiFD">,
265			<item><url id="http://www.syquest.com/" name="SyQuest EZFlyer"> and
266			<item><url id="SyQuest" name="SyQuest SparQ">
267	talehton	708	</list>
268			</p>
269
270	talehton	725	<p>All of these are about floppy disk size, store 100MBytes to
271			200MBytes (SparQ about 1.0GBytes) and are faster and more expensive
272			than floppy drives. They are connected to EIDE port, Parallel port,
273			SCSI or USB. LS-120 and Sony SuperFloppy can read and write ordinary
274			1.4MByte floppy disks.
275	talehton	708
276	talehton	729	<p>You can use these things like in the above examples where a floppy
277			disk was used, but you have to
278	talehton	725	install the devices and the device driver software before they can be
279	talehton	708	used. Then the device name depends on what kind of connection the
280			thing uses. </p>
281
282	talehton	725	<p>There is more info on using the above high capacity floppies on Linux in the
283	talehton	708	HOWTO documents. (reference to HOWTOs???)</p>
284
285
286
287			<p><strong>Somebody with experience from the above devices: please confirm my
288			guessing above or send info on how they can be used.</strong></p>
289
290			</sect1>
291
292			<sect1>
293			<heading>CD-R and CD-RW</heading>
294
295	talehton	725	<p>Meta: Capacity <= 640MBytes, speed 150 -- 600KBits/sek. Special software
296	talehton	729	needed to burn the CD. DVD-RAM</p>
297	talehton	725
298	talehton	729	<p>CD writers can be used as backup devices. Writable CD media is
299			either writable exactly once (CD-R), or erasable and rewritable
300			(CD-RW). CD-R disks can be read on ordinary CD drives, but CD-RW disks
301			need Multi-Read capability from the reader. This is good to know if
302			you plan to read the CD back on some other computer.</p>
303	talehton	725
304	talehton	729	<p>Assuming the CD writer is installed and configured correctly, and
305			you have the necessary software to write to the CD, taking backups is
306			best done with the first method in the floppy disk example above,
307			i.e. creating a Linux file system on the CD. Since the CD is a disk,
308			i.e. a random access device, using it this way is easy. Just mount it
309			and copy files or whole directory trees there.</p>
310
311			<p>Restoring is also straightforward, since the CD can be examined
312			with ordinary file system commands like <prgn>ls</prng>, and it is
313			easy to copy a single file back. You can also compare the files in the
314			backup to files in hard disk with <prgn>diff</prgn> for example. </p>
315
316			<p>Problems with CD-R are their write once -nature. They need to be
317			written all in one go, and then closed. After closing, it is not
318			possible to modify the CD, so if there is something wrong there it has
319			to be thrown away. </p>
320
321			<p>CD-RW can be erased, but my understanding is the whole disk must be
322			erased. In addition, looks like formatting a CD-RW takes about one
323			hour. </p>
324
325
326	talehton	708	</sect1>
327
328			<sect1>
329			<heading>Tapes</heading>
330
331	talehton	725	<p>Meta: Popular backup media. Wide range of speeds, capacities and cost. </p>
332	talehton	729
333			<p>Tape drives are popular backup devices. The media is relatively
334			cheap per gigabyte, and tape capacities go up to several tens of
335			gigabytes. On the other hand, the tape drives may be expensive and
336			write speeds slower than disks.</p>
337
338			<p></p>
339
340			<p></p>
341
342			<p></p>
343
344			<p></p>
345
346			<p></p>
347
348	talehton	708	</sect1>
349
350			</sect>
351
352
353			<sect>
354	talehton	688	<heading>Backup methods and software</heading>
355	talehton	708	<p>Backup methods include simply copying files to another media, using
356			dd, tar or similar program to create an archive and using special backup
357			programs.
358	talehton	688
359			<sect1><heading>Network backups</heading>
360	talehton	725	<p>Meta: Enterprise environment, Legato Networker, HP Omniback, etc. Linux clients.
361	talehton	708
362			<p>In an enterprise environment there may be a backup server running
363			some network backup software. If there are Linux clients available for
364			that software, its possible to install the Linux client, configure the
365			client machine on the backup server and start taking backups over the
366			LAN.</p>
367
368			<p>This is a low cost solution. If the backup server is already there,
369			Linux clients usually are free to download. Legato Networker and HP
370			Omniback have Linux clients available, but no technical support is
371			available from the vendor.
372
373
374			<taglist compact>
375			<tag>Legato
376	talehton	725	<item><url id="http://www.legato.com/exchange/documents/NetWorker/CG-SW.html" name="Legato Networker">
377	talehton	708
378			<tag>HP Omniback
379	talehton	725	<item><url id="http://www.hp.com/openview/products/omniback.html" name="HP Omniback">
380	talehton	708	</taglist>
381			</p>
382	talehton	688	</sect1>
383
384			<sect1><heading>Tar et al</heading>
385	talehton	725	<p>Meta: Tar, dump, dd</p>
386	talehton	688
387	talehton	708	<p>Now for some examples. </p>
388
389			<p>In Debian GNU/Linux the <prgn>tar</prgn>
390			program is GNU tar, which has several extra features. Among them is
391			support for compressing the tar file while it is created. On the
392			average, compression squeezes the file to about 50% of the
393			uncompressed size. Your mileage may vary: files that are already
394			compressed, like .zip and .gif files do not compress at all, and
395			some file compress especially well, C source code files can go to 25%
396			of the uncompressed size.</p>
397
398			<p>Taking a compressed tar file from /export/home partition goes like
399			this:
400			<example>
401			cd /export
402			tar czf /tmp/home.tgz ./home
403			</example>
404			</p>
405
406			<p></p>
407
408	talehton	688	</sect1>
409
410
411			<sect1><heading>Backup software</heading>
412	talehton	725	<p>Meta: amanda, other backup software in Debian
413	talehton	688
414
415			</sect1>
416
417
418
419			</sect>
420
421
422
423
424			<sect>
425	olly	670	<heading>Types of backup</heading>
426	talehton	725	<p>Meta: Full, incremental, differential, network, dump, level 0--9, </p>
427	talehton	729
428			<p>Meta: Check the backup can be restored, with original file owners and permissions.</p>
429
430	olly	670	</sect>
431
432			</chapt>
433
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