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|Oracle Solaris ZFS Administration Guide Oracle Solaris 10 1/13 Information Library|
The zfs send command creates a stream representation of a snapshot that is written to standard output. By default, a full stream is generated. You can redirect the output to a file or to a different system. The zfs receive command creates a snapshot whose contents are specified in the stream that is provided on standard input. If a full stream is received, a new file system is created as well. You can send ZFS snapshot data and receive ZFS snapshot data and file systems with these commands. See the examples in the next section.
The following backup solutions for saving ZFS data are available:
Enterprise backup products – If you need the following features, then consider an enterprise backup solution:
Backup media verification
File system snapshots and rolling back snapshots – Use the zfs snapshot and zfs rollback commands if you want to easily create a copy of a file system and revert to a previous file system version, if necessary. For example, to restore a file or files from a previous version of a file system, you could use this solution.
For more information about creating and rolling back to a snapshot, see Overview of ZFS Snapshots.
Saving snapshots – Use the zfs send and zfs receive commands to send and receive a ZFS snapshot. You can save incremental changes between snapshots, but you cannot restore files individually. You must restore the entire file system snapshot. These commands do not provide a complete backup solution for saving your ZFS data.
Remote replication – Use the zfs send and zfs receive commands to copy a file system from one system to another system. This process is different from a traditional volume management product that might mirror devices across a WAN. No special configuration or hardware is required. The advantage of replicating a ZFS file system is that you can re-create a file system on a storage pool on another system, and specify different levels of configuration for the newly created pool, such as RAID-Z, but with identical file system data.
Archive utilities – Save ZFS data with archive utilities such as tar, cpio, and pax or third-party backup products. Currently, both tar and cpio translate NFSv4-style ACLs correctly, but pax does not.
In addition to the zfs send and zfs receive commands, you can also use archive utilities, such as the tar and cpio commands, to save ZFS files. These utilities save and restore ZFS file attributes and ACLs. Check the appropriate options for both the tar and cpio commands.
For up-to-date information about issues with ZFS and third-party backup products, see the Solaris 10 Release Notes.
A snapshot of a ZFS file system or volume is converted into a snapshot stream by using the zfs send command. Then, you can use the snapshot stream to re-create a ZFS file system or volume by using the zfs receive command.
Depending on the zfs send options that were used to create the snapshot stream, different types of stream formats are generated.
Full stream – Consists of all dataset content from the time that the dataset was created up to the specified snapshot.
The default stream generated by the zfs send command is a full stream. It contains one file system or volume, up to and including the specified snapshot. The stream does not contain snapshots other than the snapshot specified on the command line.
Incremental stream – Consists of the differences between one snapshot and another snapshot.
A stream package is a stream type that contains one or more full or incremental streams. Three types of stream packages exist:
Replication stream package – Consists of the specified dataset and its descendents. It includes all intermediate snapshots. If the origin of a cloned dataset is not a descendent of the snapshot specified on the command line, that origin dataset is not included in the stream package. To receive the stream, the origin dataset must exist in the destination storage pool.
Consider the following list of datasets and their origins. Assume that they were created in the order that they appear below.
NAME ORIGIN pool/a - pool/a/1 - pool/a/1@clone - pool/b - pool/b/1 pool/a/1@clone pool/b/1@clone2 - pool/b/2 pool/b/1@clone2 pool/b@pre-send - pool/b/1@pre-send - pool/b/2@pre-send - pool/b@send - pool/b/1@send - pool/b/2@send -
A replication stream package that is created with the following syntax:
# zfs send -R pool/b@send ....
Consists of the following full and incremental streams:
TYPE SNAPSHOT INCREMENTAL FROM full pool/b@pre-send - incr pool/b@send pool/b@pre-send incr pool/b/1@clone2 pool/a/1@clone incr pool/b/1@pre-send pool/b/1@clone2 incr pool/b/1@send pool/b/1@send incr pool/b/2@pre-send pool/b/1@clone2 incr pool/b/2@send pool/b/2@pre-send
In the preceding output, the pool/a/1@clone snapshot is not included in the replication stream package. As such, this replication stream package can only be received in a pool that already has pool/a/1@clone snapshot.
Recursive stream package – Consists of the specified dataset and its descendents. Unlike replication stream packages, intermediate snapshots are not included unless they are the origin of a cloned dataset that is included in the stream. By default, if the origin of a dataset is not a descendent of the snapshot specified on the command line, the behavior is the similar to replication streams. However, a self-contained recursive stream, discussed below, are created in such a way that there are no external dependencies.
A recursive stream package that is created with the following syntax:
# zfs send -r pool/b@send ...
Consists of the following full and incremental streams:
TYPE SNAPSHOT INCREMENTAL FROM full pool/b@send - incr pool/b/1@clone2 pool/a/1@clone incr pool/b/1@send pool/b/1@clone2 incr pool/b/2@send pool/b/1@clone2
In the preceding output, the pool/a/1@clone snapshot is not included in the recursive stream package. As such, this recursive stream package can only be received in a pool that already has pool/a/1@clone snapshot. This behavior is similar to the replication stream package scenario described above.
Self-contained recursive stream package - Is not dependent on any datasets that are not included in the stream package. This recursive stream package is created with the following syntax:
# zfs send -rc pool/b@send ...
Consists of the following full and incremental streams:
TYPE SNAPSHOT INCREMENTAL FROM full pool/b@send - full pool/b/1@clone2 incr pool/b/1@send pool/b/1@clone2 incr pool/b/2@send pool/b/1@clone2
Notice that the self-contained recursive stream has a full stream of the pool/b/1@clone2 snapshot, making it possible receive the pool/b/1 snapshot with no external dependencies.
You can use the zfs send command to send a copy of a snapshot stream and receive the snapshot stream in another pool on the same system or in another pool on a different system that is used to store backup data. For example, to send the snapshot stream on a different pool to the same system, use syntax similar to the following:
# zfs send tank/dana@snap1 | zfs recv spool/ds01
You can use zfs recv as an alias for the zfs receive command.
If you are sending the snapshot stream to a different system, pipe the zfs send output through the ssh command. For example:
sys1# zfs send tank/dana@snap1 | ssh sys2 zfs recv newtank/dana
When you send a full stream, the destination file system must not exist.
You can send incremental data by using the zfs send -i option. For example:
sys1# zfs send -i tank/dana@snap1 tank/dana@snap2 | ssh sys2 zfs recv newtank/dana
The first argument (snap1) is the earlier snapshot and the second argument (snap2) is the later snapshot. In this case, the newtank/dana file system must already exist for the incremental receive to be successful.
Note - Accessing file information in the original received file system, can cause the incremental snapshot receive operation to fail with a message similar to this one:
cannot receive incremental stream of tank/dana@snap2 into newtank/dana: most recent snapshot of tank/dana@snap2 does not match incremental source
Consider setting the atime property to off if you need to access file information in the original received file system and if you also need to receive incremental snapshots into the received file system.
The incremental snap1 source can be specified as the last component of the snapshot name. This shortcut means you only have to specify the name after the @ sign for snap1, which is assumed to be from the same file system as snap2. For example:
sys1# zfs send -i snap1 tank/dana@snap2 | ssh sys2 zfs recv newtank/dana
This shortcut syntax is equivalent to the incremental syntax in the preceding example.
The following message is displayed if you attempt to generate an incremental stream from a different file system snapshot1:
cannot send 'pool/fs@name': not an earlier snapshot from the same fs
If you need to store many copies, consider compressing a ZFS snapshot stream representation with the gzip command. For example:
# zfs send pool/fs@snap | gzip > backupfile.gz
Both the snapshot and the file system are received.
The file system and all descendent file systems are unmounted.
The file systems are inaccessible while they are being received.
The original file system to be received must not exist while it is being transferred.
If the file system name already exists, you can use zfs rename command to rename the file system.
# zfs send tank/gozer@0830 > /bkups/gozer.083006 # zfs receive tank/gozer2@today < /bkups/gozer.083006 # zfs rename tank/gozer tank/gozer.old # zfs rename tank/gozer2 tank/gozer
If you make a change to the destination file system and you want to perform another incremental send of a snapshot, you must first roll back the receiving file system.
Consider the following example. First, make a change to the file system as follows:
sys2# rm newtank/dana/file.1
Then, perform an incremental send of tank/dana@snap3. However, you must first roll back the receiving file system to receive the new incremental snapshot. Or, you can eliminate the rollback step by using the -F option. For example:
sys1# zfs send -i tank/dana@snap2 tank/dana@snap3 | ssh sys2 zfs recv -F newtank/dana
When you receive an incremental snapshot, the destination file system must already exist.
If you make changes to the file system and you do not roll back the receiving file system to receive the new incremental snapshot or you do not use the -F option, you see a message similar to the following:
sys1# zfs send -i tank/dana@snap4 tank/dana@snap5 | ssh sys2 zfs recv newtank/dana cannot receive: destination has been modified since most recent snapshot
The following checks are performed before the -F option is successful:
If the most recent snapshot doesn't match the incremental source, neither the roll back nor the receive is completed, and an error message is returned.
If you accidentally provide the name of different file system that doesn't match the incremental source specified in the zfs receive command, neither the rollback nor the receive is completed, and the following error message is returned:
cannot send 'pool/fs@name': not an earlier snapshot from the same fs
You can send a ZFS snapshot stream with a certain file system property value, but you can specify a different local property value when the snapshot stream is received. Or, you can specify that the original property value be used when the snapshot stream is received to re-create the original file system. In addition, you can disable a file system property when the snapshot stream is received.
Use the zfs inherit -S to revert a local property value to the received value, if any. If a property does not have a received value, the behavior of the zfs inherit -S command is the same as the zfs inherit command without the -S option. If the property does have a received value, the zfs inherit command masks the received value with the inherited value until issuing a zfs inherit -S command reverts it to the received value.
You can use the zfs get -o to include the new non-default RECEIVED column. Or, use the zfs get -o all command to include all columns, including RECEIVED.
You can use the zfs send -p option to include properties in the send stream without the -R option.
You can use the zfs receive -e option to use the last element of the sent snapshot name to determine the new snapshot name. The following example sends the poola/bee/cee@1 snapshot to the poold/eee file system and only uses the last element (cee@1) of the snapshot name to create the received file system and snapshot.
# zfs list -rt all poola NAME USED AVAIL REFER MOUNTPOINT poola 134K 134G 23K /poola poola/bee 44K 134G 23K /poola/bee poola/bee/cee 21K 134G 21K /poola/bee/cee poola/bee/cee@1 0 - 21K - # zfs send -R poola/bee/cee@1 | zfs receive -e poold/eee # zfs list -rt all poold NAME USED AVAIL REFER MOUNTPOINT poold 134K 134G 23K /poold poold/eee 44K 134G 23K /poold/eee poold/eee/cee 21K 134G 21K /poold/eee/cee poold/eee/cee@1 0 - 21K -
In some cases, file system properties in a send stream might not apply to the receiving file system or local file system properties, such as the mountpoint property value, might interfere with a restore.
For example, the tank/data file system has the compression property disabled. A snapshot of the tank/data file system is sent with properties (-p option) to a backup pool and is received with the compression property enabled.
# zfs get compression tank/data NAME PROPERTY VALUE SOURCE tank/data compression off default # zfs snapshot tank/data@snap1 # zfs send -p tank/data@snap1 | zfs recv -o compression=on -d bpool # zfs get -o all compression bpool/data NAME PROPERTY VALUE RECEIVED SOURCE bpool/data compression on off local
In the example, the compression property is enabled when the snapshot is received into bpool. So, for bpool/data, the compression value is on.
If this snapshot stream is sent to a new pool, restorepool, for recovery purposes, you might want to keep all the original snapshot properties. In this case, you would use the zfs send -b command to restore the original snapshot properties. For example:
# zfs send -b bpool/data@snap1 | zfs recv -d restorepool # zfs get -o all compression restorepool/data NAME PROPERTY VALUE RECEIVED SOURCE restorepool/data compression off off received
In the example, the compression value is off, which represents the snapshot compression value from the original tank/data file system.
If you have a local file system property value in a snapshot stream and you want to disable the property when it is received, use the zfs receive -x command. For example, the following command sends a recursive snapshot stream of home directory file systems with all file system properties reserved to a backup pool, but without the quota property values:
# zfs send -R tank/home@snap1 | zfs recv -x quota bpool/home # zfs get -r quota bpool/home NAME PROPERTY VALUE SOURCE bpool/home quota none local bpool/home@snap1 quota - - bpool/home/lori quota none default bpool/home/lori@snap1 quota - - bpool/home/mark quota none default bpool/home/mark@snap1 quota - -
If the recursive snapshot was not received with the -x option, the quota property would be set in the received file systems.
# zfs send -R tank/home@snap1 | zfs recv bpool/home # zfs get -r quota bpool/home NAME PROPERTY VALUE SOURCE bpool/home quota none received bpool/home@snap1 quota - - bpool/home/lori quota 10G received bpool/home/lori@snap1 quota - - bpool/home/mark quota 10G received bpool/home/mark@snap1 quota - -
This section describes how to use the zfs send -I and -R options to send and receive more complex snapshot streams.
Keep the following points in mind when sending and receiving complex ZFS snapshot streams:
Use the zfs send -I option to send all incremental streams from one snapshot to a cumulative snapshot. Or, 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.
Use the zfs send -R option to send a replication stream of all descendent file systems. When the replication stream is received, all properties, snapshots, descendent file systems, and clones are preserved.
When using the zfs send -r option without the -c option and when using the zfs send -R option stream packages omit the origin of clones in some circumstances. For more information, see Identifying 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 are preserved.
If zfs recv -F is not specified when receiving the replication stream, dataset destroy operations are ignored. The zfs recv -F syntax in this case also retains its rollback if necessary meaning.
As with other (non zfs send -R) -i or -I cases, if -I is used, all snapshots between snapA and snapD are sent. If -i is used, only snapD (for all descendents) are sent.
To receive any of these new types of zfs send streams, the receiving system must be running a software version capable of sending them. The stream version is incremented.
However, you can access streams from older pool versions by using a newer software version. For example, you can send and receive streams created with the newer options to and from a version 3 pool. But, you must be running recent software to receive a stream sent with the newer options.
Example 6-1 Sending and Receiving Complex ZFS Snapshot Streams
A group of incremental snapshots can be combined into one snapshot by using the zfs send -I option. For example:
# zfs send -I pool/fs@snapA pool/fs@snapD > /snaps/fs@all-I
Then, you would remove snapB, snapC, and snapD.
# 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 zfs send -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
You can use the zfs send -R command to replicate a ZFS file system and all descendent file systems, up to the named snapshot. When this stream is received, all properties, snapshots, descendent file systems, and clones are preserved.
In the following example, snapshots are created 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 -
In the following example, the zfs send -R command was used to replicate the users file system and its descendents, 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 -
You can use the zfs send and zfs recv commands to remotely copy a snapshot stream representation from one system to another system. For example:
# zfs send tank/cindy@today | ssh newsys zfs recv sandbox/restfs@today
This command sends the tank/cindy@today snapshot data and receives it into the sandbox/restfs file system. The command also creates a restfs@today snapshot on the newsys system. In this example, the user has been configured to use ssh on the remote system.