$ Linux Command

Disk

dump

Back up ext2/ext3/ext4 filesystems to tape or file.

backupfilesystemexttapedumprestore

Additional Notes

dump backs up an entire ext2, ext3, or ext4 filesystem to a backup medium such as tape or a file. It operates at the filesystem level, reading inodes directly and preserving permissions, ownership, timestamps, extended attributes, and sparse file holes. It supports full and incremental backup levels (0-9), where level 0 is a full backup and higher levels back up files changed since the last lower-level dump.

The companion restore command reads the dump archive and restores files. Dump archives can be written to tape drives, regular files, or across a network using rdump/rrestore. The dump format is filesystem-specific and is only compatible with ext-family filesystems.

Syntax

dump [options] [dump-file] filesystem

Parameters

  • dump-file: The output file or device (e.g., /dev/st0 for a tape drive, or backup.dump for a file). If not specified, the default output device is used.
  • filesystem: The device or mount point of the filesystem to back up.

Common Options

  • -level: Set the dump level (0-9). Level 0 is a full backup.
  • -f file: Write to the specified file or device instead of the default.
  • -u: Update the dump record in /etc/dumpdates so incremental dumps know what was backed up.
  • -W: Show which filesystems need to be dumped based on /etc/dumpdates and /etc/fstab.
  • -w: Same as -W but only list filesystems that are mounted.
  • -a: Auto-size the dump output to fit the medium. Disables prompting for media changes.
  • -B records: Specify the tape block size in 1 KB increments.
  • -b blocksize: Set the number of kilobytes per dump record (default is 10).
  • -d density: Set tape density in bits per inch.
  • -s feet: Set tape length in feet.
  • -T date: Use the specified date instead of the current date for deciding what to dump.
  • -z level: Compress the dump output using gzip-compression level.
  • -j level: Compress the dump output using bzip2-compression level.

Examples

sudo dump -0uf /backup/root.dump /

Perform a level 0 (full) backup of the root filesystem to a file, updating /etc/dumpdates.

sudo dump -1uf /dev/st0 /home

Perform a level 1 incremental backup of /home to a tape device.

sudo dump -W

Show which filesystems need backup based on the last dump dates.

sudo dump -0u -f - / | gzip > backup.dump.gz

Write a full dump to stdout and compress it with gzip.

Practical Notes

  • dump only supports ext2, ext3, and ext4 filesystems. For other filesystem types, use filesystem-specific tools or tar/rsync.
  • Always unmount or remount a filesystem read-only before dumping if data consistency is critical.
  • Use restore -t to list the contents of a dump archive without restoring.
  • The /etc/dumpdates file tracks when each filesystem was last dumped at each level. Remove or edit it to force a full dump.
  • For remote backups, rdump writes to a remote tape device via rmt.
  • Dump archives from different machines or architectures may not be compatible.