DUMP(8) 386BSD System Manager's Manual DUMP(8)
NAME
dump - filesystem backup
SYNOPSIS
dump [0123456789fusdWn [argument ...]] [filesystem]
DESCRIPTION
Dump 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 rdump(8) for remote backups) . A
dump that is larger than the output medium is broken into multiple
volumes 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. 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.
f [file]
Write the backup to file; file may be a special device file like
/dev/rmt12 (a tape drive), /dev/rsd1c (an optical 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.
d density
Set tape density to density. The default is 1600BPI.
n Whenever dump requires operator attention, notify all operators in
the group ``operator'' by means similar to a wall(1).
s feet
Attempt to caluculate 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.
B blocks
Set the size of the dump file to the specified number of 1024-byte
blocks, superceding the tape size and density.
u Update the file /etc/dumpdates after a successful dump. The format
of /etc/dumpdates is readable 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 permission,
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:
/etc/dump 0ufds /dev/nrst1 54000 6000 /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.
FILES
/dev/rrp1g default filesystem to dump from (system dependent).
/dev/rmt8 default tape unit to dump to
/etc/dumpdates new format dump date record
/etc/fstab dump table: file systems and frequency
/etc/group to find group operator
SEE ALSO
rdump(8), restore(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 June 17, 1991 3