dump
DUMP(8) BSD System Manager's Manual DUMP(8)
NAME
dump - ext2 filesystem backup
SYNOPSIS
dump [-0123456789ackMnqSu] [-A file] [-B records] [-b blocksize]
[-d density] [-e inode numbers] [-E file] [-f file] [-F script]
[-h level] [-I nr errors] [-j compression level] [-L label]
[-Q file] [-s feet] [-T date] [-z compression level] files-to-dump
dump [-W | -w]
(The 4.3BSD option syntax is implemented for backward compatibility but
is not documented here.)
DESCRIPTION
Dump examines files on an ext2 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 for-
mer case, either the path to a mounted filesystem or the device of an
unmounted filesystem can be used. In the latter case, certain restric-
tions 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.
The following options are supported by dump:
-0-9 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 9.
-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. Since the IO system
slices all requests into chunks of MAXBSIZE (typically 64kB), it
is not possible to use a larger blocksize without having problems
later with restore(8). Therefore dump will constrain writes to
MAXBSIZE. The default blocksize is 10.
-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.
-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 car-
tridge 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 detection.
-e inodes
Exclude inodes from the dump. The inodes parameter is a comma
separated list of inode numbers (you can use stat 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 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. The device name and the cur-
rent 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 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.
-j compression 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 capa-
ble 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 compression will not be compatible with the
BSD tape format. The (optional) parameter specifies the compres-
sion 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(1) 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 direc-
tories 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 com-
patible 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 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 currently 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 man page, option MTSETDRVBUFFER, or the mt 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 dur-
ing 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 esti-
mated number of bytes it will take. This is useful with incremen-
tal 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 for-
mat of date is the same as that of ctime(3). This option is use-
ful 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 for-
mat 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. 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.
-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/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/fstab
which need to be dumped.
-z compression 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 capa-
ble 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 compression will not be compatible with the
BSD tape format. The (optional) parameter specifies the compres-
sion 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
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 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.
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:
o 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.
o 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.
ENVIRONMENT
TAPE If no -f option was specified, dump will use the device spec-
ified 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/group to find group operator
SEE ALSO
fstab(5), restore(8), rmt(8)
DIAGNOSTICS
Many, and verbose.
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 filesystems. Specifically, it does not work with FAT filesystems.
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'.
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 pro-
vided more assistance for the operator running restore.
Dump cannot do remote backups without being run as root, due to its secu-
rity 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 initial ver-
sions 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.sourceforge.net
HISTORY
A dump command appeared in Version 6 AT&T UNIX.
dump 0.4b28 April 12, 2002 dump 0.4b28
