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DUMP(8) System management commands DUMP(8)

NAME
dump - ext2/3/4 filesystem backup

SYNOPSIS
dump [-level#] [-ackMnqSuv] [-A file] [-B records] [-b blocksize] [-d density] [-D file] [-e inode numbers] [-E file] [-f
file] [-F script] [-h level] [-I nr errors] [-jcompression level] [-L label] [-Q file] [-s feet] [-T date] [-y] [-zcom-
pression level] files-to-dump

dump [-W | -w]

DESCRIPTION
Dump examines files on an ext2/3/4 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 the -f option below for doing remote backups). 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.

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 specifying cartridge media, or via 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.

files-to-dump is either a mountpoint of a filesystem or a list of files and directories to be backed up as a subset of a
filesystem. In the former case, either the path to a mounted filesystem or the device of an unmounted filesystem can be
used. In the latter case, certain restrictions are placed on the backup: -u is not allowed, the only dump level that is
supported is 0 and all the files and directories must reside on the same filesystem.

OPTIONS
The following options are supported by dump:

-level#
The dump level (any integer). A level 0, full backup, specified by -0 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. Historically only levels 0 to 9 were
usable in dump, this version is able to understand any integer as a dump level.

-a "auto-size". Bypass all tape length calculations, and write until an end-of-media indication is returned. This
works best for most modern tape drives, and is the default. 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).

-A archive_file
Archive a dump table-of-contents in the specified archive_file to be used by restore(8) to determine whether a
file is in the dump file that is being restored.

-b blocksize
The number of kilobytes per dump record. The default blocksize is 10, unless the -d option has been used to spec-
ify a tape density of 6250BPI or more, in which case the default blocksize is 32. Th maximal value is 1024. Note
however that, since the IO system slices all requests into chunks of MAXBSIZE (which can be as low as 64kB), you
can experience problems with dump(8) and restore(8) when using a higher value, depending on your kernel and/or
libC versions.

-B records
The number of 1 kB blocks per volume. Not normally required, as dump can detect end-of-media. When the specified
size is reached, dump waits for you to change the volume. This option overrides the calculation of tape size
based on length and density. If compression is on this limits the size of the compressed output per volume. Mul-
tiple values may be given as a single argument separated by commas. Each value will be used for one dump volume
in the order listed; if dump creates more volumes than the number of values given, the last value will be used for
the remaining volumes. This is useful for filling up already partially filled media (and then continuing with full
size volumes on empty media) or mixing media of different sizes.

-c Change the defaults for use with a cartridge tape drive, with a density of 8000 bpi, and a length of 1700 feet.
Specifying a cartridge drive overrides the end-of-media detection.

-d density
Set tape density to density. The default is 1600BPI. Specifying a tape density overrides the end-of-media detec-
tion.

-D file
Set the path name of the file storing the information about the previous full and incremental dumps. The default
location is /etc/dumpdates.

-e inodes
Exclude inodes from the dump. The inodes parameter is a comma separated list of inode numbers (you can use stat(1)
to find the inode number for a file or directory).

-E file
Read list of inodes to be excluded from the dump from the text file file. The file file should be an ordinary
file containing inode numbers separated by newlines.

-f file
Write the backup to file; file may be a special device file like /dev/st0 (a tape drive), /dev/rsd1c (a floppy
disk 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. 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 (which should already exist, dump doesn't create a new remote file) using rmt(8). The default
path name of the remote rmt(8) program is /etc/rmt; this can be overridden by the environment variable RMT.

-F script
Run script at the end of each tape (except for the last one). The device name and the current volume number are
passed on the command line. The script must return 0 if dump should continue without asking the user to change the
tape, 1 if dump should continue but ask the user to change the tape. Any other exit code will cause dump to abort.
For security reasons, dump reverts back to the real user ID and the real group ID before running the script.

-h level
Honor the user nodump flag UF_NODUMP 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.

-I nr errors
By default, dump will ignore the first 32 read errors on the file system before asking for operator intervention.
You can change this using this flag to any value. This is useful when running dump on an active filesystem where
read errors simply indicate an inconsistency between the mapping and dumping passes.

A value of 0 means that all read errors will be ignored.

-jcompression level
Compress every block to be written on the tape using bzlib library. This option will work only when dumping to a
file or pipe or, when dumping to a tape drive, if the tape drive is capable of writing variable length blocks. You
will need at least the 0.4b24 version of restore in order to extract compressed tapes. Tapes written using com-
pression will not be compatible with the BSD tape format. The (optional) parameter specifies the compression level
bzlib will use. The default compression level is 2. If the optional parameter is specified, there should be no
white space between the option letter and the parameter.

-k Use Kerberos authentication to talk to remote tape servers. (Only available if this option was enabled when dump
was compiled.)

-L label
The user-supplied text string label is placed into the dump header, where tools like restore(8) and file(8) can
access it. Note that this label is limited to be at most LBLSIZE (currently 16) characters, which must include the
terminating \0.

-m If this flag is specified, dump will optimise the output for inodes having been changed but not modified since the
last dump ('changed' and 'modified' have the meaning defined in stat(2) ). For those inodes, dump will save only
the metadata, instead of saving the entire inode contents. Inodes which are either directories or have been modi-
fied since the last dump are saved in a regular way. Uses of this flag must be consistent, meaning that either
every dump in an incremental dump set have the flag, or no one has it.

If you use this option, be aware that many programs that unpack files from archives (e.g. tar, rpm, unzip, dpkg)
may set files' mtimes to dates in the past. Files installed in this way may not be dumped correctly using "dump
-m" if the modified mtime is earlier than the previous level dump.

Tapes written using such 'metadata only' inodes will not be compatible with the BSD tape format or older versions
of restore.

-M Enable the multi-volume feature. The name specified with f is treated as a prefix and dump writes in sequence to
<prefix>001, <prefix>002 etc. This can be useful when dumping to files on an ext2/3/4 partition, in order to
bypass the 2GB file size limitation.

-n Whenever dump requires operator attention, notify all operators in the group operator by means similar to a
wall(1).

-q Make dump abort immediately whenever operator attention is required, without prompting in case of write errors,
tape changes etc.

-Q file
Enable the Quick File Access support. Tape positions for each inode are stored into the file file which is used by
restore (if called with parameter -Q and the filename) to directly position the tape at the file restore is cur-
rently working on. This saves hours when restoring single files from large backups, saves the tapes and the
drive's head.

It is recommended to set up the st driver to return logical tape positions rather than physical before calling
dump/restore with parameter -Q. Since not all tape devices support physical tape positions those tape devices
return an error during dump/restore when the st driver is set to the default physical setting. Please see the
st(4) man page, option MTSETDRVBUFFER , or the mt(1) man page, on how to set the driver to return logical tape
positions.

Before calling restore with parameter -Q, always make sure the st driver is set to return the same type of tape
position used during the call to dump. Otherwise restore may be confused.

This option can be used when dumping to local tapes (see above) or to local files.

-s feet
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.
Specifying the tape size overrides end-of-media detection.

-S Size estimate. Determine the amount of space that is needed to perform the dump without actually doing it, and
display the estimated number of bytes it will take. This is useful with incremental dumps to determine how many
volumes of media will be needed.

-T date
Use the specified date as the starting time for the dump instead of the time determined from looking in /etc/dump-
dates . The format of date is the same as that of ctime(3) followed by an rfc822 timezone specification: either a
plus or minus sign followed by two digits for the number of hours and two digits for the minutes. For example,
-0800 for eight hours west of Greenwich or +0230 for two hours and a half east of Greenwich. This timezone offset
takes into account daylight savings time (if applicable to the timezone): UTC offsets when daylight savings time
is in effect will be different than offsets when daylight savings time is not in effect. For backward compatibil-
ity, if no timezone is specified, a local time is assumed. This option is useful for automated dump scripts that
wish to dump over a specific period of time. The -T option is mutually exclusive from the -u option.

-u Update the file /etc/dumpdates after a successful dump. The format of /etc/dumpdates is readable by people, con-
sisting of one free format record per line: filesystem name, increment level and ctime(3) format dump date fol-
lowed by a rfc822 timezone specification (see the -u option for details). If no timezone offset is specified,
times are interpreted as local. Whenever the file is written, all dates in the file are converted to the local
time zone, without changing the UTC times. 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.

-v The -v (verbose) makes dump to print extra information which could be helpful in debug sessions.

-W Dump tells the operator what file systems need to be dumped. This information is gleaned from the files /etc/dump-
dates and /etc/fstab. The -W option causes dump to print out, for all file systems in /etc/dumpdates , and recog-
nized file systems in /etc/mtab and /etc/fstab. the most recent dump date and level, and highlights those 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 recognized filesystems in /etc/mtab and /etc/fstab which need to be dumped.

-y Compress every block to be written to the tape using the lzo library. This doesn't compress as well as the zlib
library but it's much faster. This option will work only when dumping to a file or pipe or, when dumping to a
tape drive, if the tape drive is capable of writing variable length blocks. You will need at least the 0.4b34
version of restore in order to extract compressed tapes. Tapes written using compression will not be compatible
with the BSD tape format.

-zcompression level
Compress every block to be written on the tape using zlib library. This option will work only when dumping to a
file or pipe or, when dumping to a tape drive, if the tape drive is capable of writing variable length blocks. You
will need at least the 0.4b22 version of restore in order to extract compressed tapes. Tapes written using com-
pression will not be compatible with the BSD tape format. The (optional) parameter specifies the compression level
zlib will use. The default compression level is 2. If the optional parameter is specified, there should be no
white space between the option letter and the parameter.

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 nr errors). 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 some-
thing 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 check-
point 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 ver-
bose, 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 min-
imize the number of tapes follows:

-- Always start with a level 0 backup, for example:
/sbin/dump -0u -f /dev/st0 /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.

-- After a level 0, dumps of active file systems are taken on a daily basis, 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.

Another backup strategy is the Tower of Hanoi sequence, which reuses older tapes in a way that for newer dates the avail-
able restore points are more frequent, then for older dates (see http://en.wikipedia.org/wiki/Backup_rotation_scheme for
additional information).

(The 4.3BSD option syntax is implemented for backward compatibility but is not documented here.)

ENVIRONMENT
TAPE If no -f option was specified, dump will use the device specified via TAPE as the dump device. TAPE may be of the
form tapename, host:tapename, or user@host:tapename.

RMT The environment variable RMT will be used to determine the pathname of the remote rmt(8) program.

RSH Dump uses the contents of this variable to determine the name of the remote shell command to use when doing remote
backups (rsh, ssh etc.). If this variable is not set, rcmd(3) will be used, but only root will be able to do
remote backups.

FILES
/dev/st0
default tape unit to dump to

/etc/dumpdates
dump date records

/etc/fstab
dump table: file systems and frequency

/etc/mtab
dump table: mounted file systems

/etc/group
to find group operator