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Manual page for DUMP(8)

dump, rdump - incremental file system dump


/usr/etc/dump [ options [ arguments ] ] filesystem
/usr/etc/dump [ options [ arguments ] ] filename ...
/usr/etc/rdump [ options [ arguments ] ] filesystem
/usr/etc/rdump [ options [ arguments ] ] filename ...


dump backs up all files in filesystem, or files changed after a certain date, or a specified set of files and directories, to magnetic tape, diskettes, or files. options is a string that specifies dump options, as shown below. Any arguments supplied for specific options are given as subsequent words on the command line, in the same order as that of the options listed.

If dump is called as rdump, the dump device defaults to dumphost:/dev/rmt8.

If no options are given, the default is 9u.

dump is normally used to back up a complete filesystem. To restrict the dump to a specified set of files and directories on one filesystem, list their names on the command line. In this mode the dump level is set to 0 and the u option is ignored.


The ``dump level.'' All files in the filesystem that have been modified since the last dump at a lower dump level are copied to the volume. For instance, if you did a ``level 2'' dump on Monday, followed by a ``level 4'' dump on Tuesday, a subsequent ``level 3'' dump on Wednesday would contain all files modified or added since the ``level 2'' (Monday) backup. A ``level 0'' dump copies the entire filesystem to the dump volume.
a archive-file
Create a dump table-of-contents archive in the specified file, archive-file. This file can be used by restore.8 to determine whether a file is present on a dump tape, and if so, on which volume it resides. For further information on the use of a dump archive file, see restore.8
b factor
Blocking factor. Specify the blocking factor for tape writes. The default is 20 blocks per write. Note: the blocking factor is specified in terms of 512 bytes blocks, for compatibility with tar.1 The default blocking factor for tapes of density 6250 BPI and greater is 64. The default blocking factor for cartridge tapes (c option specified) is 126. The highest blocking factor available with most tape drives is 126.
Cartridge. Use a cartridge instead of the standard half-inch reel. This sets the density to 1000 BPI, the blocking factor to 126, and the length to 425 feet. This option also sets the ``inter-record gap'' to the appropriate length. When cartridge tapes are used, and this option is not specified, dump will slightly miscompute the size of the tape. If the b, d, s or t options are specified with this option, their values will override the defaults set by this option.
d bpi
Tape density. The density of the tape, expressed in BPI, is taken from bpi. This is used to keep a running tab on the amount of tape used per reel. Default densities are:
1/2" tape
1600 BPI
1/4" cartridge
1000 BPI
2.3-Gbyte 8mm tape
54,000 BPI
Unless a higher density is specified explicitly, dump uses its default density -- even if the tape drive is capable of higher-density operation (for instance, 6250 BPI). Note: the density specified should correspond to the density of the tape device being used, or dump will not be able to handle end-of-tape properly. The d option is not compatible with the D option.
Diskette. Specify diskette as the dump media.
f dump-file
Dump file. Use dump-file as the file to dump to, instead of /dev/rmt8. If dump-file is specified as `-', dump to the standard output. If the file name argument is of the form machine:device, dump to a remote machine. Since dump is normally run by root, the name of the local machine must appear in the .rhosts file of the remote machine. If the file name argument is of the form user@machine:device, dump will attempt to execute as the specified user on the remote machine. The specified user must have a .rhosts file on the remote machine that allows root from the local machine. If dump is called as rdump, the dump device defaults to dumphost:/dev/rmt8. To direct the output to a desired remote machine, set up an alias for dumphost in the file /etc/hosts.
Notify. When this option is specified, if dump requires attention, it sends a terminal message (similar to wall.1 to all operators in the ``operator'' group.
s size
Specify the size of the volume being dumped to. When the specified size is reached, dump waits for you to change the volume. dump interprets the specified size as the length in feet for tapes, and cartridges and as the number of 1024 byte blocks for diskettes. The following are defaults:
1/2" tape
2300 feet
60-Mbyte 1/4" cartridge
425 feet
150-Mbyte 1/4" cartridge
700 feet
2.3-Gbyte 8mm
6000 feet
1422 blocks (Corresponds to a 1.44-Mbyte diskette, with one cylinder reserved for bad block information.)
t tracks
Specify the number of tracks for a cartridge tape. The t option is not compatible with the D option. The following are defaults:
60-Mbyte 1/4" cartridge (Sun2 only)
4 tracks
60-Mbyte 1/4" cartridge (all other platforms)
9 tracks
150-Mbyte 1/4" cartridge
18 tracks
Update the dump record. Add an entry to the file /etc/dumpdates, for each filesystem successfully dumped that includes the filesystem name, date, and dump level. This file can be edited by the super-user.
After writing each volume of the dump, the media is rewound and is verified against the filesystem being dumped. If any discrepancies are found, dump will respond as if a write error had occurred; the operator will be asked to mount new media, and dump will attempt to rewrite the volume. Note that any change to the filesystem, even the update of the access time on a file will cause the verification to fail. Thus, the verify option can only be used on a quiescent filesystem.
List the filesystems that need backing up. This information is gleaned from the files /etc/dumpdates and /etc/fstab. When the w option is used, all other options are ignored. After reporting, dump exits immediately.
Like w, but includes all filesystems that appear in /etc/dumpdates, along with information about their most recent dump dates and levels. Filesystems that need backing up are highlighted.


default unit to dump to
default remote unit to dump to if called as rdump
Sun386i cartridge tape dump device
Sun386i 1.44 megabyte 3.5-inch high density diskette drive dump device
Sun386i 720 kilobyte 3.5-inch low density diskette drive dump device
Sun386i 1.44 megabyte 3.5-inch high density diskette drive dump device
Sun386i 720 kilobyte 3.5-inch low density diskette drive dump device
dump date record
dump table: file systems and frequency
to find group operator


bar.1 fdformat.1 tar.1 wall.1 dump.5 fstab.5 restore.8 shutdown.8


While running, dump emits many verbose messages.

Exit Codes

Normal exit.
Startup errors encountered.
Abort - no checkpoint attempted.


Fewer than 32 read errors on the file system 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 is recommended that incremental dumps also be performed with the system running in single-user mode.

dump does not support multi-file multi-volume tapes.


Here are some examples of arguments which produce satisfactory results on a number of typical tape drives. Note that individual options can be in any order; however, the position of each following argument depends on the relative position of each option.

60-MByte cartridge (Sun2 only):
dump cdst 1000 425 4
60-MByte cartridge:
dump cdst 1000 425 9
150-MByte cartridge:
dump cdst 1000 700 18
1/2" tape:
dump dsb 1600 2300 126
2.3-GByte 8mm tape:
dump dsb 54000 6000 126

To make a full dump of a root filesystem on sd3, on a 150-MByte cartridge tape st0, use:

dump 0cdstfu 1000 700 18 /dev/rst0 /dev/sd3a

To make and verify an incremental dump at level 5 of the usr partition of sd3, on a 1/2" reel tape st1:

dump 5dsbfuv 1600 2300 126 /dev/rst1 /dev/sd3g

To make a full backup of the entire disk sd3, on a 2.3-GByte 8mm tape st2, use:

dump 0dsbfu 54000 6000 126 /dev/rst2 /dev/sd3c


Operator Intervention

dump requires operator intervention on these conditions: end of volume, end of dump, volume write error, volume 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 option, 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, as appropriate.

Since backing up a disk can involve a lot of time and effort, dump checkpoints at the start of each volume. If writing that volume fails for some reason, dump will, with operator permission, restart itself from the checkpoint after a defective volume has been replaced.

dump reports periodically, and in verbose fashion. Each report includes estimates of the percentage of the dump completed and how long it will take to complete the dump. The estimated time is given as hours:minutes.

Suggested Dump Schedule

It is vital to perform full, ``level 0'', dumps at regular intervals. When performing a full dump, bring the machine down to single-user mode using shutdown.8 While preparing for a full dump, it is a good idea to clean the tape drive and heads.

Incremental dumps allow for convenient backup and recovery on a more frequent basis of active files, with a minimum of media and time. However there are some tradeoffs. First, the interval between backups should be kept to a minimum (once a day at least). To guard against data loss as a result of a media failure (a rare, but possible occurrence), it is a good idea to capture active files on (at least) two sets of dump volumes. Another consideration is the desire to keep unnecessary duplication of files to a minimum to save both operator time and media storage. A third consideration is the ease with which a particular backed-up version of a file can be located and restored. The following four-week schedule offers a reasonable tradeoff between these goals.

	Sun 	Mon	Tue	Wed	Thu	Fri
Week 1:	Full	5	5	5	5	3
Week 2:		5	5	5	5	3
Week 3:		5	5	5	5	3
Week 4:		5	5	5	5	3

Although the Tuesday -- Friday incrementals contain ``extra copies'' of files from Monday, this scheme assures that any file modified during the week can be recovered from the previous day's incremental dump.

Process Priority of dump

dump uses multiple processes to allow it to read from the disk and write to the media concurrently. Due to the way it synchronizes between these processes, any attempt to run dump with a nice (process priority) of `-5' or better will likely make dump run slower instead of faster.

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Created by unroff & hp-tools. © by Hans-Peter Bischof. All Rights Reserved (1997).

Last modified 21/April/97