Sending and Receiving Complex ZFS Snapshot Streams

This section describes how to use the -I and -R options with the zfs send command to send and receive more complex snapshot streams.

Keep the following points in mind when sending and receiving complex ZFS snapshot streams:

  • To send all incremental streams from one snapshot to a cumulative snapshot, use the -I option. You can also use this option to send an incremental stream from the original snapshot to create a clone. The original snapshot must already exist on the receiving side to accept the incremental stream.

  • To send a replication stream of all descendant file systems, use the -R option. When the replication stream is received, all properties, snapshots, descendant file systems, and clones are preserved.

  • Using the zfs send -r command or the zfs send -R command to send package streams without the -c option will omit the origin of clones in some circumstances. For more information, see Types of ZFS Snapshot Streams.

  • Use both options to send an incremental replication stream.

    • Changes to properties are preserved, as are snapshot and file system rename and destroy operations.

    • If the -F option is not specified when receiving the replication stream, dataset destroy operations are ignored. Thus, if necessary, you can undo the receive operation and restore the file system to its previous state.

    • When sending incremental streams, if -I is used, all snapshots between snapA and snapD are sent. If -i is used, only snapD (for all descendants) snapshots are sent.

  • To receive any of these types of zfs send streams, the receiving system must be running a software version capable of sending them. The stream version is incremented.

Example 8-4 Sending and Receiving Complex ZFS Snapshot Streams

You can combine A group of incremental snapshots into one snapshot by using the -I option. For example: 

$ zfs send -I pool/fs@snapA pool/fs@snapD > /snaps/fs@all-I

You would then remove the incremental snapB, snapC, and snapD snapshots. 

$ zfs destroy pool/fs@snapB
$ zfs destroy pool/fs@snapC
$ zfs destroy pool/fs@snapD

To receive the combined snapshot, you would use the following command.

$ zfs receive -d -F pool/fs < /snaps/fs@all-I
$ zfs list
NAME                      USED  AVAIL  REFER  MOUNTPOINT
pool                      428K  16.5G    20K  /pool
pool/fs                    71K  16.5G    21K  /pool/fs
pool/fs@snapA              16K      -  18.5K  -
pool/fs@snapB              17K      -    20K  -
pool/fs@snapC              17K      -  20.5K  -
pool/fs@snapD                0      -    21K  -

You can also use the -I command to combine a snapshot and a clone snapshot to create a combined dataset. For example: 

$ zfs create pool/fs
$ zfs snapshot pool/fs@snap1
$ zfs clone pool/fs@snap1 pool/clone
$ zfs snapshot pool/clone@snapA
$ zfs send -I pool/fs@snap1 pool/clone@snapA > /snaps/fsclonesnap-I
$ zfs destroy pool/clone@snapA
$ zfs destroy pool/clone
$ zfs receive -F pool/clone < /snaps/fsclonesnap-I

To replicate a ZFS file system and all descendant file systems up to the named snapshot, use the -R option. When this stream is received, all properties, snapshots, descendant file systems, and clones are preserved.

The following example creates snapshots for user file systems. One replication stream is created for all user snapshots. Next, the original file systems and snapshots are destroyed and then recovered.

$ zfs snapshot -r users@today
$ zfs list
NAME                USED  AVAIL  REFER  MOUNTPOINT
users               187K  33.2G    22K  /users
users@today            0      -    22K  -
users/user1          18K  33.2G    18K  /users/user1
users/user1@today      0      -    18K  -
users/user2          18K  33.2G    18K  /users/user2
users/user2@today      0      -    18K  -
users/user3          18K  33.2G    18K  /users/user3
users/user3@today      0      -    18K  -
$ zfs send -R users@today > /snaps/users-R
$ zfs destroy -r users
$ zfs receive -F -d users < /snaps/users-R
$ zfs list
NAME                USED  AVAIL  REFER  MOUNTPOINT
users               196K  33.2G    22K  /users
users@today            0      -    22K  -
users/user1          18K  33.2G    18K  /users/user1
users/user1@today      0      -    18K  -
users/user2          18K  33.2G    18K  /users/user2
users/user2@today      0      -    18K  -
users/user3          18K  33.2G    18K  /users/user3
users/user3@today      0      -    18K  -

The following example uses the -R command to replicate the users file system and its descendants, and to send the replicated stream to another pool, users2. 

$ zfs create users2 mirror c0t1d0 c1t1d0
$ zfs receive -F -d users2 < /snaps/users-R
$ zfs list
NAME                 USED  AVAIL  REFER  MOUNTPOINT
users                224K  33.2G    22K  /users
users@today             0      -    22K  -
users/user1           33K  33.2G    18K  /users/user1
users/user1@today     15K      -    18K  -
users/user2           18K  33.2G    18K  /users/user2
users/user2@today       0      -    18K  -
users/user3           18K  33.2G    18K  /users/user3
users/user3@today       0      -    18K  -
users2               188K  16.5G    22K  /users2
users2@today            0      -    22K  -
users2/user1          18K  16.5G    18K  /users2/user1
users2/user1@today      0      -    18K  -
users2/user2          18K  16.5G    18K  /users2/user2
users2/user2@today      0      -    18K  -
users2/user3          18K  16.5G    18K  /users2/user3
users2/user3@today      0      -    18K  -