|DUMP(8)||System Manager's Manual||DUMP(8)|
— filesystem backup
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
dump works across networks, replacing the
functionality of the old
rdump program (though
dump may still be invoked as
rdump). See the
for more on writing backups to remote hosts.
Files can be marked with the “nodump” flag using
chflags(1), 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 option, below.
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
-f option and st(4)
for more information.
The options are as follows:
-hoption below). A level number above 0, incremental backup, tells
dumpto copy all files new or modified since the last dump of a lower level. The default level is 0.
dumpwill constrain writes to MAXBSIZE.
TAPEenvironment 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
dumprequires operator attention, notify all operators in the group “operator” by means similar to a wall(1).
dumpprompts for a new tape. It is recommended to be a bit conservative on this option. The default tape length is 2300 feet.
-Tflag is mutually exclusive from the
dumptells the operator what file systems need to be dumped. This information is gleaned from the files /etc/dumpdates and /etc/fstab. The
dumpto 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
-Wflag is set, all other options are ignored, and
-W, but prints only those filesystems which need to be dumped.
files-to-dump is either a mount point 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
disklabel(8) UID can be used. In the
latter case, certain restrictions are placed on the backup:
-u is ignored, the only dump level that is supported
-0, and all of the files must reside on the same
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 is more than a threshold
of 32). In addition to alerting all operators implied by the
dump interacts with
the operator on
dump's control terminal at times
dump can no longer proceed, or if something is
grossly wrong. All questions
must be answered by
typing “yes” or “no”, appropriately.
Since making a dump involves a lot of time and effort for full
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.
dump receives a
SIGINFO signal (see the “status”
argument of stty(1)) 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:
# /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.
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 and space:
1 2 2 2 2 2 2
This sequence requires at most eight tapes to restore, but the size of the individual dumps will be smaller:
1 2 3 4 5 6 7
This sequence seeks a compromise between backup and restore effort:
1 2 2 3 3 4 4
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 used.
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.
Many, and verbose.
dump command appeared in
Version 4 AT&T UNIX.
The 4.3BSD 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.
dump 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 fts_open(3) 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
|December 19, 2019||OpenBSD-current|