DUMP(8) System Manager's Manual DUMP(8)
dump - incremental file system dump
dump [0123456789BchfusTdWwn [argument ...]] [filesystem]
Dump copies to magnetic tape all files changed after a certain date in the filesystem.
The following options are supported by dump:
0-9 This number is the `dump level'. All files modified since the last date stored in the file /etc/dumpdates for the same filesystem at
lesser levels will be dumped. If no date is determined by the level, the beginning of time is assumed; thus the option 0 causes the
entire filesystem to be dumped.
The number of dump records per volume. This option overrides the calculation of tape size based on length and density.
c This option requires no further options. Used to specify that the tape is a cartridge drive rather than a 9-track.
Honor the user 'nodump' flags 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.
f Place the dump on the next argument file instead of the tape. If '-' is given then standard out (stdout) is written to.
u If the dump completes successfully, write the date of the beginning of the dump on file /etc/dumpdates. This file records a separate
date for each filesystem and each dump level. 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. /etc/dumpdates may be edited to change any of the
fields, if necessary. Note that /etc/dumpdates is in a format different from that which previous versions of dump maintained in
/etc/ddate, although the information content is identical.
s The size of the dump tape is specified in feet. The number of feet is taken from the next argument. When the specified size is
reached, dump will wait for reels to be changed. The default tape size is 2300 feet.
d The density of the tape, expressed in BPI, is taken from the next argument. This is used in calculating the amount of tape used per
reel. The default is 1600.
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 with the u option.
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 immedi-
w Is like W, but prints only those filesystems which need to be dumped.
n Whenever dump requires operator attention, notify by means similar to a wall(1) all of the operators in the group "operator".
If no arguments are given, the key is assumed to be 9u and a default file system is dumped to the default tape.
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 num-
ber 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.
Now a short suggestion on how to perform dumps. Start with a full level 0 dump
Next, dumps of active file systems are taken on a daily basis, using a modified Tower of Hanoi algorithm, with this sequence of dump lev-
3 2 5 4 7 6 9 8 9 9 ...
For the daily dumps, a set of 10 tapes per dumped file system is used on a cyclical basis. Each week, a level 1 dump is taken, and the
daily Hanoi sequence repeats with 3. For weekly dumps, a set of 5 tapes per dumped file system is used, also on a cyclical basis. Each
month, a level 0 dump is taken on a set of fresh tapes that is saved forever.
/dev/rxp0a default filesystem to dump from
/dev/rmt0 default tape unit to dump to
/etc/ddate old format dump date record (obsolete after -J option)
/etc/dumpdates new format dump date record
/etc/fstab Dump table: file systems and frequency
/etc/group to find group operator
restor(8), rdump(8), dump(5), fstab(5), dumpdir(8)
Many, and verbose.
Sizes are based on 1600 BPI blocked tape; the raw magtape device has to be used to approach these densities. 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.
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 restor.
4th Berkeley Distribution DUMP(8)