NAME

SYNOPSIS

DESCRIPTION

The following global options are available:

-v

Display verbose messages showing the essential system commands involved in the operation.

-h

Display a short usage help message and exit.

-d subdir

Set the subdirectory on filesystems under which snapshots are placed. The default is the conventional .snap subdirectory dump(8) uses, too.

The following commands are available:

snapshot list [fs ...]

List all existing snapshots on all filesystems or just the particular filesystems specified by fs. The output shows both actual disk-space user usage ("User", "User%") and the disk-space snapshot usage ("Snap", "Snap%").

snapshot make [-g max-generations] fs:tag[.generation]

Makes a new snapshot generation named tag on filesystem fs, located in the file fs/subdir/tag.generation. If the generation part is omitted, generation 0 is used. All older generations (with numbers greater than generation) are rotated and all obsoleted generations (with numbers greater or equal to max-generations) are removed. Keep in mind that a maximum total number of 20 snapshots can be created on a UFS filesystem only. A max-generations number of 0 effectively deletes all snapshots on filesystem fs of name tag only.

snapshot mount [-o mount-option] fs:tag[.generation] dir

Mounts the fs snapshot tag.generation (or tag.0 if generation is omitted) under dir by attaching the snapshot file to the next free md(4) device and mounting this device read-only onto the target directory. If options -o are specified, they are passed-through to mount(8).

snapshot umount dir

Unmounts a snapshot by umounting the md(4) device from dir, deattaching the snapshot file from the corresponding md(4) device and deleting the device.

snapshot visit fs:tag[.generation]

This is just a convenience command which mounts the specified filesystem on /mnt, temporarily changes to /mnt, starts an interactive shell there for inspecting the snapshot content, and upon exit from the shell immediately unmounts the snapshot again.

EXAMPLE

root# snapshot list /var
Filesystem          User   User%     Snap   Snap%  Snapshot
root# snapshot make -g4 /var:test
root# snapshot list /var
Filesystem          User   User%     Snap   Snap%  Snapshot
/var              1172MB   14.8%      4MB    0.1%  test.0
root# snapshot make -g4 /var:test
root# snapshot list /var
Filesystem          User   User%     Snap   Snap%  Snapshot
/var              1176MB   14.8%      4MB    0.1%  test.0
/var              1176MB   14.8%      4MB    0.1%  test.1
root# snapshot make -g4 /var:test
root# snapshot list /var
Filesystem          User   User%     Snap   Snap%  Snapshot
/var              1181MB   14.9%      4MB    0.1%  test.0
/var              1181MB   14.9%      4MB    0.1%  test.1
/var              1181MB   14.9%      4MB    0.1%  test.2
root# snapshot make -g4 /var:test
root# snapshot list /var
Filesystem          User   User%     Snap   Snap%  Snapshot
/var              1186MB   15.0%      4MB    0.1%  test.0
/var              1186MB   15.0%      4MB    0.1%  test.1
/var              1186MB   15.0%      4MB    0.1%  test.2
/var              1186MB   15.0%      4MB    0.1%  test.3
root# snapshot make -g4 /var:test
root# snapshot list /var
Filesystem          User   User%     Snap   Snap%  Snapshot
/var              1186MB   15.0%      4MB    0.1%  test.0
/var              1186MB   15.0%      4MB    0.1%  test.1
/var              1186MB   15.0%      4MB    0.1%  test.2
/var              1186MB   15.0%      4MB    0.1%  test.3
root# snapshot mount /var:test.2 /mnt
root# ls /mnt
account    cron       heimdal    mail       opkg       spool
at         db         lib        msgs       preserve   tmp
backups    empty      log        named      run        yp
root# snapshot umount /mnt
root# snapshot make -g0 /var:test
root# snapshot list /var
Filesystem          User   User%     Snap   Snap%  Snapshot
root# _

By using an amd(8) map /usr/local/etc/amd.map.snap containing

/defaults type:=program
*         mount:="/usr/local/sbin/snapshot snapshot mount /${key} ${fs}";\
          unmount:="/usr/local/sbin/snapshot snapshot umount ${fs}"

and a /etc/rc.conf configuration of

amd_enable="YES"
amd_flags="-a /.am -c 1800 -w 60 -l syslog /snap /usr/local/etc/amd.map.snap"

even non-privileged users can access arbitrary snapshots fs:tag[generation] by just accessing /snap/fs:tag[generation]. For instance, if a snapshot hourly.2 exists on filesystem /var one can then access an old state of file /var/tmp/foo.txt by simply accessing the path /snap/var:hourly.2/tmp/foo.txt.

SEE ALSO

HISTORY

AUTHORS