[-T date] files-to-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. 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. This can
be enforced by using the -a
works across networks, replacing the
functionality of the old rdump
may still be invoked as
). See the -f
option for more on writing backups to remote hosts.
Files can be marked with the “nodump” flag using
, settable only by
the file's owner or the superuser. Files with this flag set will only be
dumped during full backups. When set on a directory, “nodump”
effectively deselects the whole subtree from being dumped, though it will
still be scanned. See also the -h
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, 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.
Rewinding or ejecting tape features after a close operation on a tape device
depend on the name of the tape unit device used. See the
for more information.
The options are as follows:
- 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 a lower level. The default level is 0.
- “auto-size”. Bypass all tape length
considerations, and enforce writing until an end-of-media indication is
returned. This option is recommended for most modern tape drives. Use of
this option is particularly recommended when appending to an existing
tape, or using a tape drive with hardware compression (where you can never
be sure about the compression ratio).
- The number of kilobytes per volume, rounded down to a
multiple of the blocksize. This option overrides the calculation of tape
size based on length and density.
- The number of kilobytes per dump record. Since the I/O
system slices all requests into chunks of MAXBSIZE (typically 64KB), it is
not possible to use a larger blocksize without having problems later with
dump will constrain writes to MAXBSIZE.
- Change the defaults for use with a cartridge tape drive,
with a density of 8000 bpi, and a length of 1700 feet.
- Set tape density to
density. The default is 1600BPI.
- Write the backup to file;
file may be a special device file like
/dev/rst0 (a tape drive),
/dev/rsd1c (a disk drive), an ordinary file,
or ‘-’ (the standard output). See also the
TAPE environment variable, below.
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 be 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
- Honor the user “nodump” flag (see above),
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
- Whenever dump requires
operator attention, notify all operators in the group
“operator” by means similar to a
- Display an estimate of the backup size and the number of
tapes required, and exit without actually performing the dump.
- 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.
- 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 flag is mutually exclusive
from the -u flag.
- Update the file /etc/dumpdates
after a successful dump. The format of
/etc/dumpdates is human readable, consisting
of one free format record per line: filesystem name (defaults to
disklabel(8) UID when
possible), 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. If a list of files or subdirectories is being
dumped (as opposed to an entire filesystem), then
-u is ignored.
- dump tells the operator what
file systems need to be dumped. This information is gleaned from the files
-W flag 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 flag is set, all other options are
ignored, and dump exits immediately.
- Same as -W, but prints only
those filesystems which need to be dumped.
is either a mountpoint of a
filesystem or a list of files and directories on a single filesystem to be
backed up as a subset of the filesystem. In the former case, either the path
to a mounted filesystem, the device of an unmounted filesystem or the
UID can be used.
In the latter case, certain restrictions are placed on the backup:
is ignored, the only dump level that is
supported is -0
, and all of the files must reside
on the same filesystem.
requires operator intervention on these
conditions: end of tape, end of dump, tape write error, tape open error or
disk read error (if there is more than a threshold of 32). In addition to
alerting all operators implied by the -n
interacts with the operator on
's control terminal at times when
can no longer proceed, or if something is
grossly wrong. All questions dump
be answered by typing “yes” or
Since making a dump involves a lot of time and effort for full dumps,
checkpoints itself at the start of each tape
volume. If writing that volume fails for some reason,
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.
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.
signal (see the
“status” argument of
) whilst a backup is in
progress, statistics on the amount completed, current transfer rate, and
estimated finished time, will be written to the standard error output.
In the event of a catastrophic disk event, the time required to restore all the
necessary backup tapes or files to disk is dependent on the levels of the
dumps taken. A few methods of staggering incremental dumps to either minimize
backup effort or restore effort follow:
- Always start with a level 0 backup, for example:
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.
# /sbin/dump -0u -f /dev/nrst1 /usr/src
- After the level 0 dump, backups of active file systems
are taken on each day in a cycle of a week. Once a week, a level 1 dump is
taken. The other days of the week a higher level dump is done.
The following cycle needs at most three tapes to restore to a given point in
time, but the dumps at the end of the weekly cycle will require more time
This sequence requires at most eight tapes to restore, but the size of the
individual dumps will be smaller:
This sequence seeks a compromise between backup and restore effort:
The weekly level 1 dumps should be done on a set of tapes that is used
cyclically. For the daily dumps a tape per day of the week can be
- After several months or so, the daily and weekly tapes
should get rotated out of the dump cycle and fresh tapes brought in.
- The default file to use instead of
/dev/rst0. See also
- default tape unit to dump to
- raw SCSI tape interface
- dump date records
- dump table: file systems and frequency
- to find group operator
Many, and verbose.
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.
command appeared in
Version 4 AT&T UNIX
option syntax is implemented for backward
compatibility but is not documented here.
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.
with the -W
flag does not report filesystems that have
never been recorded in /etc/dumpdates
, even if
listed in /etc/fstab
When dumping a list of files or subdirectories, access privileges are required
to scan the directory (as this is done via the
routines rather than
directly accessing the filesystem).
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