NAME
xfsdump - XFS filesystem incremental dump utility
SYNOPSIS
xfsdump -h
xfsdump [ options ] -f dest [ -f dest ... ] filesystem
xfsdump [ options ] - filesystem
xfsdump -I [ subopt=value ... ]
DESCRIPTION
xfsdump backs up files and their attributes in a filesystem. The files
are dumped to storage media, a regular file, or standard output.
Options allow the operator to have all files dumped, just files that
have changed since a previous dump, or just files contained in a list
of pathnames.
The xfsrestore(8) utility re-populates a filesystem with the contents
of the dump.
Each invocation of xfsdump dumps just one filesystem. That invocation
is termed a dump session. The dump session splits the filesystem into
one or more dump streams, one per destination. The split is done in
filesystem inode number (ino) order, at boundaries selected to equalize
the size of each stream. Furthermore, the breakpoints between streams
may be in the middle of very large files (at extent boundaries) if
necessary to achieve reasonable stream size equalization. Each dump
stream can span several media objects, and a single media object can
contain several dump streams. The typical media object is a tape
cartridge. The media object records the dump stream as one or more
media files. A media file is a self-contained partial dump, intended
to minimize the impact of media dropouts on the entire dump stream at
the expense of increasing the time required to complete the dump. By
default only one media file is written unless a media file size is
specified using the -d option. Other techniques, such as making a
second copy of the dump image, provide more protection against media
failures than multiple media files will.
However, the current implementation in Linux only supports one
destination and running single threaded. Therefore, the above comments
regarding multiple streams describe the possible future capabilities.
xfsdump maintains an online dump inventory in
/var/lib/xfsdump/inventory. The -I option displays the inventory
contents hierarchically. The levels of the hierarchy are: filesystem,
dump session, stream, and media file.
The options to xfsdump are:
-a Specifies that files for which the Data Migration Facility (DMF)
has complete offline copies (dual-state files) be treated as if
they were offline (OFL). This means that the file data will not
be dumped by xfsdump, resulting in a smaller dump file. If the
file is later restored the file data is still accessible through
DMF. If both ’-a option’ and ’-z option’ are specified, the ’-a
option’ takes precedence (see ’-z option’ below).
-b blocksize
Specifies the blocksize, in bytes, to be used for the dump. The
same blocksize must be specified to restore the tape. If the -m
option is not used, then -b does not need to be specified.
Instead, a default blocksize of 1Mb will be used.
-c progname
Use the specified program to alert the operator when a media
change is required. The alert program is typically a script to
send a mail or flash a window to draw the operator’s attention.
-d filesize
Specifies the size, in megabytes, of dump media files. If not
specified, xfsdump will dump data to tape using a single media
file per media object. The specified media file size may need to
be adjusted if, for example, xfsdump cannot fit a media file onto
a single tape.
-e Allow files to be excluded from the dump. This will cause xfsdump
to skip files which have the "no dump" file attribute set. See the
"Excluding individual files" section below for details on setting
this file attribute. Files with an extended attribute named
"SGI_XFSDUMP_SKIP_FILE" will also be skipped, however this method
is deprecated and xfsdump will stop checking for it in a future
version.
-f dest [ -f dest ... ]
Specifies a dump destination. A dump destination can be the
pathname of a device (such as a tape drive), a regular file or a
remote tape drive (see rmt(8)). This option must be omitted if
the standard output option (a lone - preceding the source
filesystem specification) is specified.
-l level
Specifies a dump level of 0 to 9. The dump level determines the
base dump to which this dump is relative. The base dump is the
most recent dump at a lesser level. A level 0 dump is absolute -
all files are dumped. A dump level where 1 <= level <= 9 is
referred to as an incremental dump. Only files that have been
changed since the base dump are dumped. Subtree dumps (see the -s
option below) cannot be used as the base for incremental dumps.
-m Use the minimal tape protocol for non-scsi tape destinations or
remote tape destinations which are not scsi Linux tape drives nor
IRIX tape drives. This option cannot be used without specifying a
blocksize to be used (see -b option above).
-o Overwrite the tape. With this option, xfsdump does not read the
tape first to check the contents. This option may be used if
xfsdump is unable to determine the block size of a tape .
-p interval
Causes progress reports to be printed at the specified interval.
interval is given in seconds. The progress report indicates how
many files have been dumped, the total number of files to dump,
the percentage of data dumped, and the elapsed time.
-q Destination tape drive is a QIC tape. QIC tapes only use a 512
byte blocksize, for which xfsdump must make special allowances.
-s pathname [ -s pathname ... ]
Restricts the dump to files contained in the specified pathnames
(subtrees). A pathname must be relative to the mount point of the
filesystem. For example, if a filesystem is mounted at /d2, the
pathname argument for the directory /d2/users is ‘‘users’’. A
pathname can be a file or a directory; if it is a directory, the
entire hierarchy of files and subdirectories rooted at that
directory is dumped. Subtree dumps cannot be used as the base for
incremental dumps (see the -l option above).
-t file
Sets the dump time to the modification time of file rather than
using the current time. xfsdump uses the dump time to determine
what files need to be backed up during an incremental dump. This
option should be used when dumping snapshots so that the dump time
matches the time the snapshot was taken. Otherwise files modified
after a snapshot is taken may be skipped in the next incremental
dump.
-v verbosity
-v subsys=verbosity[,subsys=verbosity,...]
Specifies the level of detail used for messages displayed during
the course of the dump. The verbosity argument can be passed as
either a string or an integer. If passed as a string the following
values may be used: silent, verbose, trace, debug, or nitty. If
passed as an integer, values from 0-5 may be used. The values 0-4
correspond to the strings already listed. The value 5 can be used
to produce even more verbose debug output.
The first form of this option activates message logging across all
dump subsystems. The second form allows the message logging level
to be controlled on a per-subsystem basis. The two forms can be
combined (see the example below). The argument subsys can take one
of the following values: general, proc, drive, media, inventory,
inomap and excluded_files.
For example, to dump the root filesystem with tracing activated
for all subsystems:
# xfsdump -v trace -f /dev/tape /
To enable debug-level tracing for drive and media operations:
# xfsdump -v drive=debug,media=debug -f /dev/tape /
To enable tracing for all subsystems, and debug level tracing for
drive operations only:
# xfsdump -v trace,drive=debug -f /dev/tape /
To list files that will be excluded from the dump:
# xfsdump -e -v excluded_files=debug -f /dev/tape /
-z size
Specifies the maximum size, in kilobytes, of files to be included
in the dump. Files over this size, will be excluded from the
dump, except for DMF dual-state files when ’-a option’ is
specified (see ’-a option’ above). When specified, ’-a option’
takes precedence over ’-z option’. The size is an estimate based
on the number of disk blocks actually used by the file, and so
does not include holes. In other words, size refers to the amount
of space the file would take in the resulting dump. On an
interactive restore, the skipped file is visible with xfsrestore’s
’ls’ and while you can use the ’add’ and ’extract’ commands,
nothing will be restored.
-A Do not dump extended file attributes. When dumping a filesystem
managed within a DMF environment this option should not be used.
DMF stores file migration status within extended attributes
associated with each file. If these attributes are not preserved
when the filesystem is restored, files that had been in migrated
state will not be recallable by DMF. Note that dumps containing
extended file attributes cannot be restored with older versions of
xfsrestore(8).
-B session_id
Specifies the ID of the dump session upon which this dump session
is to be based. If this option is specified, the -l (level) and
-R (resume) options are not allowed. Instead, xfsdump determines
if the current dump session should be incremental and/or resumed,
by looking at the base session’s level and interrupted attributes.
If the base session was interrupted, the current dump session is a
resumption of that base at the same level. Otherwise, the current
dump session is an incremental dump with a level one greater than
that of the base session. This option allows incremental and
resumed dumps to be based on any previous dump, rather than just
the most recent.
-E Pre-erase media. If this option is specified, media is erased
prior to use. The operator is prompted for confirmation, unless
the -F option is also specified.
-F Don’t prompt the operator. When xfsdump encounters a media object
containing non-xfsdump data, xfsdump normally asks the operator
for permission to overwrite. With this option the overwrite is
performed, no questions asked. When xfsdump encounters end-of-
media during a dump, xfsdump normally asks the operator if another
media object will be provided. With this option the dump is
instead interrupted.
-I Displays the xfsdump inventory (no dump is performed). xfsdump
records each dump session in an online inventory in
/var/lib/xfsdump/inventory. xfsdump uses this inventory to
determine the base for incremental dumps. It is also useful for
manually identifying a dump session to be restored. Suboptions to
filter the inventory display are described later.
-J Inhibits the normal update of the inventory. This is useful when
the media being dumped to will be discarded or overwritten.
-L session_label
Specifies a label for the dump session. It can be any arbitrary
string up to 255 characters long.
-M label [ -M label ... ]
Specifies a label for the first media object (for example, tape
cartridge) written on the corresponding destination during the
session. It can be any arbitrary string up to 255 characters
long. Multiple media object labels can be specified, one for each
destination.
-O options_file
Insert the options contained in options_file into the beginning of
the command line. The options are specified just as they would
appear if typed into the command line. In addition, newline
characters (\n) can be used as whitespace. The options are placed
before all options actually given on the command line, just after
the command name. Only one -O option can be used. Recursive use
is ignored. The source filesystem cannot be specified in
options_file.
-R Resumes a previously interrupted dump session. If the most recent
dump at this dump’s level (-l option) was interrupted, this dump
contains only files not in the interrupted dump and consistent
with the incremental level. However, files contained in the
interrupted dump that have been subsequently modified are re-
dumped.
-T Inhibits interactive dialogue timeouts. When the -F option is not
specified, xfsdump prompts the operator for labels and media
changes. Each dialogue normally times out if no response is
supplied. This option prevents the timeout.
-Y length
Specify I/O buffer ring length. xfsdump uses a ring of output
buffers to achieve maximum throughput when dumping to tape drives.
The default ring length is 3. However, this is only supported
when running multi-threaded which has not been done for Linux yet
- making this option benign.
- A lone - causes the dump stream to be sent to the standard output,
where it can be piped to another utility such as xfsrestore(8) or
redirected to a file. This option cannot be used with the -f
option. The - must follow all other options and precede the
filesystem specification.
The filesystem, filesystem, can be specified either as a mount point or
as a special device file (for example, /dev/dsk/dks0d1s0). The
filesystem must be mounted to be dumped.
NOTES
Dump Interruption
A dump can be interrupted at any time and later resumed. To interrupt,
type control-C (or the current terminal interrupt character). The
operator is prompted to select one of several operations, including
dump interruption. After the operator selects dump interruption, the
dump continues until a convenient break point is encountered (typically
the end of the current file). Very large files are broken into smaller
subfiles, so the wait for the end of the current file is brief.
Dump Resumption
A previously interrupted dump can be resumed by specifying the -R
option. If the most recent dump at the specified level was
interrupted, the new dump does not include files already dumped, unless
they have changed since the interrupted dump.
Media Management
A single media object can contain many dump streams. Conversely, a
single dump stream can span multiple media objects. If a dump stream
is sent to a media object already containing one or more dumps, xfsdump
appends the new dump stream after the last dump stream. Media files
are never overwritten. If end-of-media is encountered during the
course of a dump, the operator is prompted to insert a new media object
into the drive. The dump stream continuation is appended after the
last media file on the new media object.
Inventory
Each dump session updates an inventory database in
/var/lib/xfsdump/inventory. xfsdump uses the inventory to determine
the base of incremental and resumed dumps.
This database can be displayed by invoking xfsdump with the -I option.
The display uses tabbed indentation to present the inventory
hierarchically. The first level is filesystem. The second level is
session. The third level is media stream (currently only one stream is
supported). The fourth level lists the media files sequentially
composing the stream.
The following suboptions are available to filter the display.
-I depth=n
(where n is 1, 2, or 3) limits the hierarchical depth of the
display. When n is 1, only the filesystem information from the
inventory is displayed. When n is 2, only filesystem and session
information are displayed. When n is 3, only filesystem, session
and stream information are displayed.
-I level=n
(where n is the dump level) limits the display to dumps of that
particular dump level.
The display may be restricted to media files contained in a specific
media object.
-I mobjid=value
(where value is a media ID) specifies the media object by its
media ID.
-I mobjlabel=value
(where value is a media label) specifies the media object by its
media label.
Similarly, the display can be restricted to a specific filesystem.
-I mnt=mount_point
(that is, [hostname:]pathname), identifies the filesystem by
mountpoint. Specifying the hostname is optional, but may be
useful in a clustered environment where more than one host can be
responsible for dumping a filesystem.
-I fsid=filesystem_id
identifies the filesystem by filesystem ID.
-I dev=device_pathname
(that is, [hostname:]device_pathname) identifies the filesystem by
device. As with the mnt filter, specifying the hostname is
optional.
More than one of these suboptions, separated by commas, may be
specified at the same time to limit the display of the inventory to
those dumps of interest. However, at most four suboptions can be
specified at once: one to constrain the display hierarchy depth, one to
constrain the dump level, one to constrain the media object, and one to
constrain the filesystem.
For example, -I depth=1,mobjlabel="tape 1",mnt=host1:/test_mnt would
display only the filesystem information (depth=1) for those filesystems
that were mounted on host1:/test_mnt at the time of the dump, and only
those filesystems dumped to the media object labeled "tape 1".
Dump records may be removed (pruned) from the inventory using the
xfsinvutil program.
An additional media file is placed at the end of each dump stream.
This media file contains the inventory information for the current dump
session. Its contents may be merged back into the online inventory
database at a later time using xfsrestore(1M).
The inventory files stored in /var/lib/xfsdump are not included in the
dump, even if that directory is contained within the filesystem being
dumped. Including the inventory in the dump may lead to loss or
corruption of data, should an older version be restored overwriting the
current version. To backup the xfsdump inventory, the contents of
/var/lib/xfsdump should be copied to another location which may then be
safely dumped. Upon restoration, those files may be copied back into
/var/lib/xfsdump, overwriting whatever files may be there, or
xfsinvutil(1M) may be used to selectively merge parts of the restored
inventory back into the current inventory. Prior to version 1.1.8,
xfsdump would include the /var/lib/xfsdump directory in the dump. Care
should be taken not to overwrite the /var/lib/xfsdump directory when
restoring an old dump, by either restoring the filesystem to another
location or by copying the current contents of /var/lib/xfsdump to a
safe place prior to running xfsrestore(1M).
Labels
The operator can specify a label to identify the dump session and a
label to identify a media object. The session label is placed in every
media file produced in the course of the dump, and is recorded in the
inventory.
The media label is used to identify media objects, and is independent
of the session label. Each media file on the media object contains a
copy of the media label. An error is returned if the operator
specifies a media label that does not match the media label on a media
object containing valid media files. Media labels are recorded in the
inventory.
UUIDs
UUIDs (Universally Unique Identifiers) are used in three places: to
identify the filesystem being dumped (using the filesystem UUID, see
xfs(5) for more details), to identify the dump session, and to identify
each media object. The inventory display (-I) includes all of these.
Dump Level Usage
The dump level mechanism provides a structured form of incremental
dumps. A dump of level level includes only files that have changed
since the most recent dump at a level less than level. For example,
the operator can establish a dump schedule that involves a full dump
every Friday and a daily incremental dump containing only files that
have changed since the previous dump. In this case Friday’s dump would
be at level 0, Saturday’s at level 1, Sunday’s at level 2, and so on,
up to the Thursday dump at level 6.
The above schedule results in a very tedious restore procedure to fully
reconstruct the Thursday version of the filesystem; xfsrestore would
need to be fed all 7 dumps in sequence. A compromise schedule is to
use level 1 on Saturday, Monday, and Wednesday, and level 2 on Sunday,
Tuesday, and Thursday. The Monday and Wednesday dumps would take
longer, but the worst case restore requires the accumulation of just
three dumps, one each at level 0, level 1, and level 2.
Quotas
If the filesystem being dumped contains user quotas, xfsdump will use
xfs_quota(8) to store the quotas in a file called xfsdump_quotas in the
root of the filesystem to be dumped. This file will then be included in
the dump. Upon restoration, xfs_quota (8) can be used to reactivate
the quotas for the filesystem. Note, however, that the xfsdump_quotas
file will probably require modification to change the filesystem or
UIDs if the filesystem has been restored to a different partition or
system. Group and project quotas will be handled in a similar fashion
and saved in files called xfsdump_quotas_group and xfsdump_quotas_proj
, respectively.
Excluding individual files
It may be desirable to exclude particular files or directories from the
dump. The -s option can be used to limit the dump to a specified
directory, and the -z option can be used to exclude files over a
particular size. Additionally, when xfsdump is run with the -e option,
files that are tagged with the "no dump" file attribute will not be
included in the dump. The chattr(1) command can be used to set this
attribute on individual files or entire subtrees.
To tag an individual file for exclusion from the dump:
$ chattr +d file
To tag all files in a subtree for exclusion from the dump:
$ chattr -R +d directory
Note that any new files or directories created in a directory which has
the "no dump" attribute set will automatically inherit this attribute.
Also note that xfsdump does not check directories for the "no dump"
attribute.
Care should be taken to note which files have been tagged. Under
normal operation, xfsdump will only report the number of files it will
skip. The -v excluded_files=debug option, however, will cause xfsdump
to list the inode numbers of the individual files affected.
EXAMPLES
To perform a level 0, single stream dump of the root filesystem to a
locally mounted tape drive, prompting for session and media labels when
required:
# xfsdump -f /dev/tape /
To specify session and media labels explicitly:
# xfsdump -L session_1 -M tape_0 -f /dev/tape /
To perform a dump to a remote tape using the minimal rmt protocol and a
set blocksize of 64k:
# xfsdump -m -b 65536 -f otherhost:/dev/tape /
To perform a level 0, multi-stream dump to two locally mounted tape
drives:
# xfsdump -L session_2 -f /dev/rmt/tps4d6v -M tape_1 \
-f /dev/rmt/tps5d6v -M tape_2 /
To perform a level 1 dump relative to the last level 0 dump recorded in
the inventory:
# xfsdump -l 1 -f /dev/tape /
To copy the contents of a filesystem to another directory (see
xfsrestore(8)):
# xfsdump -J - / | xfsrestore -J - /new
FILES
/var/lib/xfsdump/inventory
dump inventory database
SEE ALSO
attr(1), rmt(8), xfsrestore(8), xfsinvutil(8), xfs_quota(8),
attr_get(2).
DIAGNOSTICS
The exit code is 0 on normal completion, non-zero if an error occurs or
the dump is terminated by the operator.
For all verbosity levels greater than 0 (silent) the final line of the
output shows the exit status of the dump. It is of the form:
xfsdump: Dump Status: code
Where code takes one of the following values: SUCCESS (normal
completion), INTERRUPT (interrupted), QUIT (media no longer usable),
INCOMPLETE (dump incomplete), FAULT (software error), and ERROR
(resource error). Every attempt will be made to keep both the syntax
and the semantics of this log message unchanged in future versions of
xfsdump. However, it may be necessary to refine or expand the set of
exit codes, or their interpretation at some point in the future.
The message ‘‘xfsdump: WARNING: unable to open directory: ino N:
Invalid argument’’ can occur with filesystems which are actively being
modified while xfsdump is running. This can happen to either directory
or regular file inodes - affected files will not end up in the dump,
files below affected directories will be placed in the orphanage
directory by xfsrestore.
BUGS
xfsdump does not dump unmounted filesystems.
The dump frequency field of /etc/fstab is not supported.
xfsdump uses the alert program only when a media change is required.
xfsdump requires root privilege (except for inventory display).
xfsdump can only dump XFS filesystems.
The media format used by xfsdump can only be understood by xfsrestore.
xfsdump does not know how to manage CD-ROM or other removable disk
drives.
xfsdump can become confused when doing incremental or resumed dumps if
on the same machine you dump two XFS filesystems and both filesystems
have the same filesystem identifier (UUID). Since xfsdump uses the
filesystem identifier to identify filesystems, xfsdump maintains one
combined set of dump inventories for both filesystems instead of two
sets of dump inventories. This scenario can happen only if dd or some
other block-by-block copy program was used to make a copy of an XFS
filesystem. See xfs_copy(8) and xfs(5) for more details.
xfsdump(8)