DUMP(8) BSD System Manager's Manual DUMP(8)
NAME
dump, rdump -- filesystem backup
ALERT
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.
SYNOPSIS
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.)
DESCRIPTION
The dump command 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.
The following options are supported by dump:
-0-9 Dump levels. A level 0, full backup, guarantees the entire file system is copied (but see also
the -h option below). A level number above 0, incremental backup, tells dump to copy all files
new or modified since the last dump of the same or lower level. The default level is 9.
-B records
The number of dump records per volume. This option overrides the calculation of tape size
based on length and density.
-b blocksize
The number of kilobytes per dump record.
-c Modify the calculation of the default density and tape size to be more appropriate for car-tridge cartridge
tridge tapes.
-d density
Set tape density to density. The default is 1600BPI.
-f file
Write the backup to file; file may be a special device file like /dev/rmt12 (a tape drive),
/dev/rdisk1s3 (a disk drive), an ordinary file, or `-' (the standard output). Multiple file
names may be given as a single argument separated by commas. Each file will be used for one
dump volume in the order listed; if the dump requires more volumes than the number of names
given, the last file name will used for all remaining volumes after prompting for media
changes. If the name of the file is of the form ``host:file'', or ``user@host:file'', dump
writes to the named file on the remote host using rmt(8).
-h level
Honor the user ``nodump'' flag only for dumps at or above the given level. The default honor
level is 1, so that incremental backups omit such files but full backups retain them.
-n Whenever dump requires operator attention, notify all operators in the group ``operator'' by
means similar to a wall(1).
-s feet
Attempt to calculate the amount of tape needed at a particular density. If this amount is
exceeded, dump prompts for a new tape. It is recommended to be a bit conservative on this
option. The default tape length is 2300 feet.
-T date
Use the specified date as the starting time for the dump instead of the time determined from
looking in /etc/dumpdates. The format of date is the same as that of ctime(3). This option is
useful for automated dump scripts that wish to dump over a specific period of time. The -T
option is mutually exclusive from the -u option.
-u Update the file /etc/dumpdates after a successful dump. The format of /etc/dumpdates is read-able readable
able by people, consisting of one free format record per line: filesystem name, increment level
and ctime(3) format dump date. There may be only one entry per filesystem at each level. The
file /etc/dumpdates may be edited to change any of the fields, if necessary.
-W Dump tells the operator what file systems need to be dumped. This information is gleaned from
the files /etc/dumpdates and /etc/fstab. The -W option causes dump to print out, for each file
system in /etc/dumpdates the most recent dump date and level, and highlights those file systems
that should be dumped. If the -W option is set, all other options are ignored, and dump exits
immediately.
-w Is like W, but prints only those filesystems which need to be dumped.
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, permission,
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:
oo 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.
oo 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.
FILES
/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 ALSO
restore(8), rmt(8), dump(5), fstab(5)
DIAGNOSTICS
Many, and verbose.
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
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