dump, rdump -- filesystem backup
UFS SUPPORT IS IN THE PROCESS OF BEING DEPRECATED. This copy of dump is supplied only for completeness and is expected to have deficiencies. It will likely disappear in the future.
dump [-0123456789cnu] [-B records] [-b blocksize] [-d density] [-f file] [-h level] [-s feet] [-T date] filesystem dump -W | -w
rdump is an alternate name for dump.
(The 4.3BSD option syntax is implemented for backward compatibility, but is not documented here.)
examines files on a filesystem and determines which files need to be backed up. These files are copied to the given disk, tape or other storage medium for safe keeping (see the -f option below for doing remote backups). A dump that is larger than the output medium is broken into multiple volumes. On most media the size is determined by writing until an end-of-media indication is returned. On media that cannot reliably return an end-of-media indication (such as some cartridge tape drives) each volume is of a fixed size; the actual size is determined by the tape size and density and/or block count options below. By default, the same output file name is used for each volume after prompting the operator to change media.
Dump requires operator intervention on these conditions: end of tape, end of dump, tape write error, tape open error or disk read error (if there are more than a threshold of 32). In addition to alerting all operators implied by the -n key, dump interacts with the operator on dump's control terminal at times when dump can no longer proceed, or if something is grossly wrong. All questions dump poses must be answered by typing ``yes'' or ``no'', appropriately.
Since making a dump involves a lot of time and effort for full dumps, dump checkpoints itself at the start of each tape volume. If writing that volume fails for some reason, dump will, with operator per- mission, restart itself from the checkpoint after the old tape has been rewound and removed, and a new tape has been mounted.
Dump tells the operator what is going on at periodic intervals, including usually low estimates of the number of blocks to write, the number of tapes it will take, the time to completion, and the time to the tape change. The output is verbose, so that others know that the terminal controlling dump is busy, and will be for some time.
In the event of a catastrophic disk event, the time required to restore all the necessary backup tapes or files to disk can be kept to a minimum by staggering the incremental dumps. An efficient method of staggering incremental dumps to minimize the number of tapes follows:
o Always start with a level 0 backup, for example:
/sbin/dump -0u -f /dev/nrst1 /usr/src
This should be done at set intervals, say once a month or once every two months, and on a set of fresh tapes that is saved forever.
o After a level 0, dumps of active file systems are taken on a daily basis, using a modified Tower of Hanoi algorithm, with this sequence of dump levels:
3 2 5 4 7 6 9 8 9 9 ...
For the daily dumps, it should be possible to use a fixed number of tapes for each day, used on a weekly basis. Each week, a level 1 dump is taken, and the daily Hanoi sequence repeats beginning with 3. For weekly dumps, another fixed set of tapes per dumped file system is used, also on a cyclical basis.
After several months or so, the daily and weekly tapes should get rotated out of the dump cycle and fresh tapes brought in.
/dev/rmt8 default tape unit to dump to /etc/dumpdates dump date records /etc/fstab dump table: file systems and frequency /etc/group to find group operator
SEE restore(8), rmt(8), dump(5), fstab(5)
Dump exits with zero status on success. Startup errors are indicated with an exit code of 1; abnormal termination is indicated with an exit code of 3.
BUGS Fewer than 32 read errors on the filesystem are ignored.
Each reel requires a new process, so parent processes for reels already written just hang around until the entire tape is written.
Dump with the -W or -w options does not report filesystems that have never been recorded in /etc/dumpdates, even if listed in /etc/fstab.
It would be nice if dump knew about the dump sequence, kept track of the tapes scribbled on, told the operator which tape to mount when, and provided more assistance for the operator running restore.
HISTORY A dump command appeared in Version 6 AT&T UNIX.
4th Berkeley Distribution May 1, 1995 4th Berkeley Distribution