dump
DUMP(8) System management commands DUMP(8)
NAME
dump - ext2/3 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] [-zcompression level] files-to-dump
dump [-W | -w]
DESCRIPTION
Dump examines files on an ext2/3 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, guaran-
tees 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 9. 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 exist-
ing 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 specify 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 den-
sity. If compression is on this limits the size of the com-
pressed output per volume. Multiple 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. Specify-
ing a tape density overrides the end-of-media detection.
-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 incre-
mental 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 com-
pressed tapes. Tapes written using compression will not be com-
patible 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 com-
piled.)
-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 (cur-
rently 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 modified 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.
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 partition, in order to bypass the 2GB file size limita-
tion.
-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 currently working on.
This saves hours when restoring single files from large back-
ups, 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/dumpdates .
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 sav-
ings time is in effect will be different than offsets when day-
light 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, consisting of
one free format record per line: filesystem name, increment
level and ctime(3) format dump date followed by a rfc822 time-
zone specification (see the -u option for details). If no time-
zone offset is specified, times are interpreted as local. When-
ever 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/dumpdates and
/etc/fstab. The -W option causes dump to print out, for all
file systems in /etc/dumpdates , and regognized 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 com-
pressed tapes. Tapes written using compression will not be com-
patible with the BSD tape format. The (optional) parameter
specifies the compression level zlib will use. The default com-
pression 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 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 permis-
sion, 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.
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 minimize 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, using a modified Tower of Hanoi algorithm, 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 num-
ber 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.
(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 speci-
fied 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
SEE ALSO
fstab(5), restore(8), rmt(8)
DIAGNOSTICS
Many, and verbose.
COMPATIBILITY
The format of the /etc/dumpdates file has changed in release 0.4b34,
however, the file will be read correctly with either pre-0.4b34 or
0.4b34 and later versions of dump provided that the machine on which
dump is run did not change timezones (which should be a fairly rare
occurence).
EXIT STATUS
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.
BUGS
It might be considered a bug that this version of dump can only handle
ext2/3 filesystems. Specifically, it does not work with FAT filesys-
tems.
Fewer than 32 read errors (change this with -I) on the filesystem are
ignored. If noticing read errors is important, the output from dump
can be parsed to look for lines that contain the text ’read error’.
When a read error occurs, dump prints out the corresponding physical
disk block and sector number and the ext2/3 logical block number. It
doesn’t print out the corresponing file name or even the inode number.
The user has to use debugfs(8), commands ncheck and icheck to trans-
late the ext2blk number printed out by dump into an inode number, then
into a file name.
Each reel requires a new process, so parent processes for reels
already written just hang around until the entire tape is written.
The estimated number of tapes is not correct if compression is on.
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 restore.
Dump cannot do remote backups without being run as root, due to its
security history. Presently, it works if you set it setuid (like it
used to be), but this might constitute a security risk. Note that you
can set RSH to use a remote shell program instead.
AUTHOR
The dump/restore backup suite was ported to Linux’s Second Extended
File System by Remy Card <card@Linux.EU.Org>. He maintained the ini-
tial versions of dump (up and including 0.4b4, released in january
1997).
Starting with 0.4b5, the new maintainer is Stelian Pop
<stelian@popies.net>.
AVAILABILITY
The dump/restore backup suite is available from <http://dump.source-
forge.net>
HISTORY
A dump command appeared in Version 6 AT&T UNIX.
BSD version 0.4b39 of January 21, 2005 DUMP(8)
