3.7. Backing Up and Restoring XFS File Systems

XFS file system backup and restoration involve these utilities:
  • xfsdump for creating the backup
  • xfsrestore for restoring from backup

3.7.1. Features of XFS Backup and Restoration

Backup

You can use the xfsdump utility to:
  • Perform backups to regular file images.
    Only one backup can be written to a regular file.
  • Perform backups to tape drives.
    The xfsdump utility also allows you to write multiple backups to the same tape. A backup can span multiple tapes.
    To back up multiple file systems to a single tape device, simply write the backup to a tape that already contains an XFS backup. This appends the new backup to the previous one. By default, xfsdump never overwrites existing backups.
  • Create incremental backups.
    The xfsdump utility uses dump levels to determine a base backup to which other backups are relative. Numbers from 0 to 9 refer to increasing dump levels. An incremental backup only backs up files that have changed since the last dump of a lower level:
    • To perform a full backup, perform a level 0 dump on the file system.
    • A level 1 dump is the first incremental backup after a full backup. The next incremental backup would be level 2, which only backs up files that have changed since the last level 1 dump; and so on, to a maximum of level 9.
  • Exclude files from a backup using size, subtree, or inode flags to filter them.

Restoration

The xfsrestore utility restores file systems from backups produced by xfsdump. The xfsrestore utility has two modes:
  • The simple mode enables users to restore an entire file system from a level 0 dump. This is the default mode.
  • The cumulative mode enables file system restoration from an incremental backup: that is, level 1 to level 9.
A unique session ID or session label identifies each backup. Restoring a backup from a tape containing multiple backups requires its corresponding session ID or label.
To extract, add, or delete specific files from a backup, enter the xfsrestore interactive mode. The interactive mode provides a set of commands to manipulate the backup files.

3.7.2. Backing Up an XFS File System

This procedure describes how to back up the content of an XFS file system into a file or a tape.

Procedure 3.2. Backing Up an XFS File System

  • Use the following command to back up an XFS file system: 
    # xfsdump -l level [-L label] -f backup-destination path-to-xfs-filesystem
    • Replace level with the dump level of your backup. Use 0 to perform a full backup or 1 to 9 to perform consequent incremental backups.
    • Replace backup-destination with the path where you want to store your backup. The destination can be a regular file, a tape drive, or a remote tape device. For example, /backup-files/Data.xfsdump for a file or /dev/st0 for a tape drive.
    • Replace path-to-xfs-filesystem with the mount point of the XFS file system you want to back up. For example, /mnt/data/. The file system must be mounted.
    • When backing up multiple file systems and saving them on a single tape device, add a session label to each backup using the -L label option so that it is easier to identify them when restoring. Replace label with any name for your backup: for example, backup_data.

Example 3.4. Backing up Multiple XFS File Systems

  • To back up the content of XFS file systems mounted on the /boot/ and /data/ directories and save them as files in the /backup-files/ directory: 
    # xfsdump -l 0 -f /backup-files/boot.xfsdump /boot
# xfsdump -l 0 -f /backup-files/data.xfsdump /data
  • To back up multiple file systems on a single tape device, add a session label to each backup using the -L label option: 
    # xfsdump -l 0 -L "backup_boot" -f /dev/st0 /boot
# xfsdump -l 0 -L "backup_data" -f /dev/st0 /data

Additional Resources

  • For more information about backing up XFS file systems, see the xfsdump(8) man page.

3.7.3. Restoring an XFS File System from Backup

This procedure describes how to restore the content of an XFS file system from a file or tape backup.

Prerequisites

Procedure 3.3. Restoring an XFS File System from Backup

  • The command to restore the backup varies depending on whether you are restoring from a full backup or an incremental one, or are restoring multiple backups from a single tape device: 
    # xfsrestore [-r] [-S session-id] [-L session-label] [-i]
             -f backup-location restoration-path
    • Replace backup-location with the location of the backup. This can be a regular file, a tape drive, or a remote tape device. For example, /backup-files/Data.xfsdump for a file or /dev/st0 for a tape drive.
    • Replace restoration-path with the path to the directory where you want to restore the file system. For example, /mnt/data/.
    • To restore a file system from an incremental (level 1 to level 9) backup, add the -r option.
    • To restore a backup from a tape device that contains multiple backups, specify the backup using the -S or -L options.
      The -S lets you choose a backup by its session ID, while the -L lets you choose by the session label. To obtain the session ID and session labels, use the xfsrestore -I command.
      Replace session-id with the session ID of the backup. For example, b74a3586-e52e-4a4a-8775-c3334fa8ea2c. Replace session-label with the session label of the backup. For example, my_backup_session_label.
    • To use xfsrestore interactively, use the -i option.
      The interactive dialog begins after xfsrestore finishes reading the specified device. Available commands in the interactive xfsrestore shell include cd, ls, add, delete, and extract; for a complete list of commands, use the help command.

Example 3.5. Restoring Multiple XFS File Systems

To restore the XFS backup files and save their content into directories under /mnt/: 
# xfsrestore -f /backup-files/boot.xfsdump /mnt/boot/
# xfsrestore -f /backup-files/data.xfsdump /mnt/data/
To restore from a tape device containing multiple backups, specify each backup by its session label or session ID: 
# xfsrestore -f /dev/st0 -L "backup_boot" /mnt/boot/
# xfsrestore -f /dev/st0 -S "45e9af35-efd2-4244-87bc-4762e476cbab" /mnt/data/

Informational Messages When Restoring a Backup from a Tape

When restoring a backup from a tape with backups from multiple file systems, the xfsrestore utility might issue messages. The messages inform you whether a match of the requested backup has been found when xfsrestore examines each backup on the tape in sequential order. For example: 
xfsrestore: preparing drive
xfsrestore: examining media file 0
xfsrestore: inventory session uuid (8590224e-3c93-469c-a311-fc8f23029b2a) does not match the media header's session uuid (7eda9f86-f1e9-4dfd-b1d4-c50467912408)
xfsrestore: examining media file 1
xfsrestore: inventory session uuid (8590224e-3c93-469c-a311-fc8f23029b2a) does not match the media header's session uuid (7eda9f86-f1e9-4dfd-b1d4-c50467912408)
[...]
The informational messages keep appearing until the matching backup is found.

Additional Resources

  • For more information about restoring XFS file systems, see the xfsrestore(8) man page.