This document gives a quick intro into the backup scheme that is maintained in GPS. It also explains how to perform backups and restores of files and filesystems.
Backups of the Unix computers in GPS are performed using the Amanda software package. This is a freely available package. URL's of interest include:
The Amanda backup software designates two types of machines:
The master host is also a client machine, since it backs itself up. The master host contains one or more tape drives or a tape stacker and one or more holding disks reserved for holding the backups of filesystems before they are sent to tape. The holding disk is typically several gigabytes large.
When a backup starts, the master machine performs the following steps:
Different configurations of hosts and filesystems to backup, types of backups, compression options, etc, are possible under Amanda. All of the options are saved under a particular "configuration." A configuration is known by a single label, such as DailySet1. The option and log files for a particular configuration are saved under directories named with the configuration's name. Under the directory are several important files. I only list here the files that you could commonly change.
DailySet1/amanda.conf configuration options to amanda
DailySet1/chg-generic.conf configuration for multiple tape drives
DailySet1/disklist list of hosts and filesystems to backup
The Amanda programs and configuration files are owned by a particular user. All Amanda programs must be run by this user for successful operation.
In GPS, kipuka is the master host. Kipuka is a SparcStation 5 running Solaris 2.5 and is located in 250 South Mudd. It has attached to it two Exabyte 8505XL's, one in an Andataco box and one in a Sun box. The devices are known as /dev/rmt/0 and /dev/rmt/1. Kipuka has two holding directories, /export/home1/amanda and /export/home2/amanda, both roughly 3 gigabytes large. Both are striped filesystems.
The amanda software lives under /opt/amanda and is owned by the
amanda user (username amanda). When executing any amanda program,
make sure that you are logged in on kipuka as amanda. The
configuration name used for the daily GPS backups is
DailySet1. The amanda user on kipuka has the following
crontab entry which runs the backups at 12:01 AM everyday and
ejects the tape when the backups are completed:
1 0 * * * /opt/amanda/libexec/cronjob
Mail is sent to the users listed in the amanda.conf file when
the backups are done.
Here's a picture of the directories and the information they contain:
.../bin executables for users
.../libexec executables for Amanda software
.../config directory containing different configurations
.../config/DailySet1 directory of configuration files for daily GPS backups
.../adm directory containing log files for configurations
.../adm/DailySet1 directory of log files for daily GPS backups
.../docs directory of documentation for Amanda
.../man manual pages for Amanda
For daily backups to be performed, new tapes must be inserted into the tape drives on kipuka. If you are using a brand new tape, the tape must be labeled with the following command:
amlabel DailySet1 DailySet1.???
Replace ??? with the next number in the sequence of tape labels. For example, at the time of writing, the last tape in the sequence is labeled as DailySet1.104, so the next tape to be labeled is DailySet1.105.
Check that the tape is loaded by doing:
mt -f /dev/rmt/0 stat
Continue doing this until you see this:
kipuka% mt -f /dev/rmt/0 stat
Exabyte EXB-8500 8mm tape drive:
sense key(0x0)= No Additional Sense residual= 0 retries= 0
file no= 0 block no= 0
Now execute the following command:
amcheck DailySet1
Something similar to this should be seen:
kipuka% amcheck DailySet1
Amanda Tape Server Host Check
-----------------------------
/export/home2/amanda: 3006679 KB disk space available, that's plenty.
NOTE: skipping tape-writeable test.
Tape DailySet1.047 label ok.
Server check took 14.817 seconds.
Amanda Backup Client Hosts Check
--------------------------------
Client check: 27 hosts checked in 5.247 seconds, 0 problems found.
(brought to you by Amanda 2.3.0)
Any problems with down hosts, not enough space on the holding disk, or tape problems will be shown here.
Finally, rewind the tape:
mt -f /dev/rmt0 rew
To restore a file or a filesystem, log in as amanda on kipuka. We then need to find out which tapes are necessary to do a complete restore. The amadmin program should be used as follows, replacing HOSTNAME with the proper host name:
amadmin DailySet1 info HOSTNAME
This shows information such as this:
Current info for earth /export/earth/u1:
Stats: dump rates (kps), Full: 67.4, 68.5, 61.4
Incremental: 9.9, 5.5, 23.5
compressed size, Full: 48.2%, 48.4%, 48.4%
Incremental: 48.7%, 36.9%, 28.2%
Dumps: lev datestmp tape file origK compK secs
0 19951225 DailySet1.045 128 886275 427197 6334
1 19951226 DailySet1.046 125 2062 1005 101
2 19951224 DailySet1.044 59 1490 551 100
3 19951122 DailySet1.011 122 14909 9517 219
This shows on which tape and on what date a particular level dump was done. If we needed to restore earth's /export/earth/u1 partition, we would need tapes DailySet1.045 and DailySet1.046. Note that we would not need tapes DailySet1.044 and DailySet1.011, since these tapes were made before the last level 0 dump.
Insert tape DailySet1.045 into kipuka's tape drive and execute the following commands
cd /export/home2/amanda
amrestore -c /dev/rmt/0bn earth /export/earth/u1
This will leave a gzip'ed, dump formatted file in the current directory. Removing the -c option from amrestore will cause amrestore to uncompress the data before saving the dump file to disk. However, to reduce network traffic, we can uncompress the data on the remote host, earth in this case. Now log into earth as root and execute the following commands:
cd /export/earth/u1
/opt/amanda/libexec/zcat /net/kipuka/export/home2/amanda/earth*0 | restore xvf -
If you are restoring only a single file, then you can name the file in the restore command.