dump - phpMan

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 car-
tridge 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 direc-
tories 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 directo-
ries 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, 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. 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 compres-
sion (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 how-
ever 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. 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. Specifying a tape den-
sity 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 sep-
arated 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 compression 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 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 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(4) man page, option MTSETDRVBUFFER , or
the mt(1) man page, on how to set the driver to return logical tape posi-
tions.

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 vol-
umes 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 Green-
wich or +0230 for two hours and a half east of Greenwich. This timezone off-
set takes into account daylight savings time (if applicable to the time-
zone): UTC offsets when daylight savings time is in effect will be different
than offsets when daylight savings time is not in effect. For backward com-
patibility, if no timezone is specified, a local time is assumed. This
option is useful for automated dump scripts that wish to dump over a spe-
cific 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 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 help-
ful in debug sessions.

-W Dump tells the operator what file systems need to be dumped. This informa-
tion 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
compressed tapes. Tapes written using compression 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 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 check-
points 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 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 lev-
els:
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 cycli-
cal 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 doc-
umented 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