红帽全球峰会8.7. Backup and Restoration of XFS File Systems
XFS file system backup and restoration involves two utilities:
xfsdump and xfsrestore.
To backup or dump an XFS file system, use the
xfsdump utility. Red Hat Enterprise Linux 6 supports backups to tape drives or regular file images, and also allows multiple dumps to be written to the same tape. The xfsdump utility also allows a dump to span multiple tapes, although only one dump can be written to a regular file. In addition, xfsdump supports incremental backups, and can exclude files from a backup using size, subtree, or inode flags to filter them.
In order to support incremental backups,
xfsdump uses dump levels to determine a base dump to which a specific dump is relative. The -l option specifies a dump level (0-9). To perform a full backup, perform a level 0 dump on the file system (that is, /path/to/filesystem), as in:
xfsdump -l 0 -f /dev/device /path/to/filesystem
# xfsdump -l 0 -f /dev/device /path/to/filesystemxfsdump -l 0 -f /dev/device /path/to/filesystemxfsdump -l 0 -f /dev/device /path/to/filesystemxfsdump -l 0 -f /dev/device /path/to/filesystem注意
The
-f option specifies a destination for a backup. For example, the /dev/st0 destination is normally used for tape drives. An xfsdump destination can be a tape drive, regular file, or remote tape device.
In contrast, an incremental backup will only dump files that changed since the last level 0 dump. A level 1 dump is the first incremental dump after a full dump; the next incremental dump would be level 2, and so on, to a maximum of level 9. So, to perform a level 1 dump to a tape drive:
xfsdump -l 1 -f /dev/st0 /path/to/filesystem
# xfsdump -l 1 -f /dev/st0 /path/to/filesystemxfsdump -l 1 -f /dev/st0 /path/to/filesystem
Conversely, the
xfsrestore utility restores file systems from dumps produced by xfsdump. The xfsrestore utility has two modes: a default simple mode, and a cumulative mode. Specific dumps are identified by session ID or session label. As such, restoring a dump requires its corresponding session ID or label. To display the session ID and labels of all dumps (both full and incremental), use the -I option:
xfsrestore -I
# xfsrestore -I
This will provide output similar to the following:
例 8.4. Session ID and labels of all dumps
Simple Mode for xfsrestore
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The simple mode allows users to restore an entire file system from a level 0 dump. After identifying a level 0 dump's session ID (that is,
session-ID), restore it fully to /path/to/destination using:
xfsrestore -f /dev/st0 -S session-ID /path/to/destination
# xfsrestore -f /dev/st0 -S session-ID /path/to/destinationxfsrestore -f /dev/st0 -S session-ID /path/to/destinationxfsrestore -f /dev/st0 -S session-ID /path/to/destinationxfsrestore -f /dev/st0 -S session-ID /path/to/destination注意
The
-f option specifies the location of the dump, while the -S or -L option specifies which specific dump to restore. The -S option is used to specify a session ID, while the -L option is used for session labels. The -I option displays both session labels and IDs for each dump.
Cumulative Mode for xfsrestore
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The cumulative mode of
xfsrestore allows file system restoration from a specific incremental backup, for example, level 1 to level 9. To restore a file system from an incremental backup, simply add the -r option:
xfsrestore -f /dev/st0 -S session-ID -r /path/to/destination
# xfsrestore -f /dev/st0 -S session-ID -r /path/to/destinationxfsrestore -f /dev/st0 -S session-ID -r /path/to/destinationxfsrestore -f /dev/st0 -S session-ID -r /path/to/destinationxfsrestore -f /dev/st0 -S session-ID -r /path/to/destinationInteractive Operation
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The
xfsrestore utility also allows specific files from a dump to be extracted, added, or deleted. To use xfsrestore interactively, use the -i option, as in:
xfsrestore -f /dev/st0 -i
The interactive dialogue will begin after
xfsrestore finishes reading the specified device. Available commands in this dialogue include cd, ls, add, delete, and extract; for a complete list of commands, use help.
For more information about dumping and restoring XFS file systems, refer to
man xfsdump and man xfsrestore.
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