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.
