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Oracle Solaris ZFS Administration Guide     Oracle Solaris 11 Express 11/10
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Document Information

Preface

1.  Oracle Solaris ZFS File System (Introduction)

2.  Getting Started With Oracle Solaris ZFS

3.  Oracle Solaris ZFS and Traditional File System Differences

4.  Managing Oracle Solaris ZFS Storage Pools

5.  Managing ZFS Root Pool Components

6.  Managing Oracle Solaris ZFS File Systems

7.  Working With Oracle Solaris ZFS Snapshots and Clones

Overview of ZFS Snapshots

Creating and Destroying ZFS Snapshots

Holding ZFS Snapshots

Renaming ZFS Snapshots

Displaying and Accessing ZFS Snapshots

Disk Space Accounting for ZFS Snapshots

Rolling Back a ZFS Snapshot

Identifying ZFS Snapshot Differences (zfs diff)

Managing Automatic ZFS Snapshots

How to Manage Automatic ZFS Snapshots

How to Recover Automatic ZFS Snapshots (GNOME File Manager)

Overview of ZFS Clones

Creating a ZFS Clone

Destroying a ZFS Clone

Replacing a ZFS File System With a ZFS Clone

Sending and Receiving ZFS Data

Saving ZFS Data With Other Backup Products

Sending a ZFS Snapshot

Receiving a ZFS Snapshot

Applying Different Property Values to a ZFS Snapshot Stream

Sending and Receiving Complex ZFS Snapshot Streams

Remote Replication of ZFS Data

8.  Using ACLs and Attributes to Protect Oracle Solaris ZFS Files

9.  Oracle Solaris ZFS Delegated Administration

10.  Oracle Solaris ZFS Advanced Topics

11.  Oracle Solaris ZFS Troubleshooting and Pool Recovery

A.  Oracle Solaris ZFS Version Descriptions

Index

Sending and Receiving ZFS Data

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:

Saving ZFS Data With Other Backup Products

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 Oracle Solaris 11 Express Release Notes or the ZFS FAQ, available here:

http://hub.opensolaris.org/bin/view/Community+Group+zfs/faq/#backupsoftware

Sending a ZFS Snapshot

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:

host1# zfs send tank/dana@snap1 | ssh host2 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:

host1# zfs send -i tank/dana@snap1 tank/dana@snap2 | ssh host2 zfs recv newtank/dana

Note that 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.

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:

host1# zfs send -i snap1 tank/dana@snap2 > ssh host2 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

Receiving a ZFS Snapshot

Keep the following key points in mind when you receive a file system snapshot:

For example:

# 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:

host2# 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:

host1# zfs send -i tank/dana@snap2 tank/dana@snap3 | ssh host2 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:

host1# zfs send -i tank/dana@snap4 tank/dana@snap5 | ssh host2 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:

Applying Different Property Values to a ZFS Snapshot Stream

You can send a ZFS snapshot stream with a certain file system property, but you can specify a different local property value when the snapshot stream is received. Or, you can specify that the original property value is used when the snapshot stream is received to recreate the original file system. In addition, you can also disable a file system property when the snapshot stream is received.

In some cases, file system properties in a send stream might not apply to the receiving file system or the local file system properties might interfere with a restore, such as a mountpoint property value.

For example, the tank/data file system has the compression property is disabled. A snapshot of the tank/data file system is sent with properties (-p) 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 above example, the compression property is enabled when the snapshot was received into the 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 option 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 above 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, send 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@1020 | zfs recv -x quota bpool/home
# zfs get -r quota bpool/home
NAME                    PROPERTY  VALUE  SOURCE
bpool/home              quota     none   default
bpool/home@1020         quota     -      -
bpool/home/cindys       quota     none   local
bpool/home/cindys@1020  quota     -      -
bpool/home/tom          quota     none   local
bpool/home/tom@1020     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@1020 | zfs recv bpool/home
# zfs get -r quota bpool/home
NAME                     PROPERTY  VALUE  SOURCE
bpool/home               quota     none   default
bpool/home@1020          quota     -      -
bpool/home/cindys        quota     2G     received
bpool/home/cindys@1020   quota     -      -
bpool/home/tom           quota     4G     received
bpool/home/tom@1020      quota     -      -

Sending and Receiving Complex ZFS Snapshot Streams

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:

Example 7-1 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 dataset 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  -

Remote Replication of ZFS Data

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.