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Man Pages

Manual Reference Pages  -  ZXFER (8)


zxfer - transfer ZFS filesystems, snapshots, properties, files and directories


     Normal | zfs send/receive mode
     Rsync mode
     Ex1 - Backup a pool (including snapshots and properties)
     Ex2 - Backup pool to HDD
     Ex3 - Restore a pool
     Ex4 - Backup a filesystem
     Ex5 - Restore a filesystem
     Ex6 - Recursive directory backup
     Ex7 - Recursive directory restore
     Ex8 - Backup FreeBSD 8.2 root mirror
     Ex9 - Restore FreeBSD 8.2 root mirror
     Ex10 - Migrate a filesystem
     Ex11 - Compress a filesystem
     Ex12 - Compress a filesystem...
     Ex13 - Backup a pool to a remote host
     Ex14 - Restore a pool from a remote host
Exit Values
See Also


zxfer [-dFnPsUv] [-k-| -e ] [-b-| -B ]
.Brq -N path/to/src | -R path/to/src [-m [c FMRI|pattern[ FMRI|pattern]...]]] [-D ’progress dialog options’] [-I properties,to,ignore] [-O user@host] [-T user@host] [-o option1=value1,option2=value2...] [-g days] destination zxfer
.Brq -S [-dilpPnv] [-k-| -e ] [-b-| -B ] [-f /path/to/rsfile]
.Brq -R /path/to/src1,path/to/src2... | -N /path/to/src1,path/to/src2... [-o option1=value1,option2=value2...] [-E pattern] [-L value] [-u snapshot] destination zxfer [-h]

Where destination is a ZFS filesystem e.g. poolname/fsname


The zxfer utility performs two main functions. It can replicate ZFS filesystems (including snapshots and properties) using zfs(8) send to do the heavy lifting.

It can also transfer files and directories and the filesystems underlying them using rsync(1). It will first recursively snapshot those filesystems so that an atomic snapshot of all files and directories exists as a base. It then creates a replica of the source filesystem hierarchy down to the pool level at the destination. It then transfers the files and directories. This is desirable when we have different snapshotting regimes on source and destination, and want to copy across the latest contents of the filesystem(s).

Both zfs(8) send and rsync(1) use checksums/hashes to verify that the data copied to the destination is the same data that was sent from the source, so we have a similar degree of surety of end-to-end data integrity as the ZFS filesystem itself.

Either method allows for the properties of each filesystem to be transferred and specific properties overridden as necessary. For example, compression, readonly, and copies are properties that are likely to be useful to override if we are using this utility to make backups. If the destination filesystems do not exist, zxfer will automatically create them.

Both methods also allow the backup and restore of the original filesystem properties so that if it is desirable to backup the filesystem(s) for archival purposes using compression etc. as overrides, the original properties may be restored without the user having to make a note of what those original properties were.

IMPORTANT: Note that switching between these two modes is done with -S. Depending on the mode, the workings of an option may be nonexistent, subtly or grossly different. Don’t assume an option works the exact same way that it did with the other mode.

Note also that zxfer should be run from root, as to do anything useful zfs(8) must also be run from root.

Note that at present, the usage of spaces in zfs(8) filesystem names is NOT supported. There is no plan to support it without someone else doing the coding or a good funding proposal coming my way.


You MUST read, understand and agree to the disclaimer in the BSD license before applying any of these examples or using zxfer. (See the file "COPYING" that should have been included with this utility.) I eat my own cooking - I use zxfer as per the examples given and as my primary form of backup. That being said, you are strongly urged to have a look at the script and try it out on some non-risky pools and filesystems before using it in production. At this stage, straying too far from the given examples will probably furnish you with the material to submit some bug reports. Run a backup before using it and don’t shoot me if something goes wrong. This software is about beta level, which means that if you are going to use it for backups you should treat it more like alpha level software - i.e. trust it at your own risk.

Modifying an example first is a good way to start using the script, as there are some options (e.g. -d and -F in normal mode) that are in practice always used.


zxfer in Normal mode as a backup/restore solution is designed to be used hand-in-hand with a regular snapshotting regime. If there is no regular snapshotting regime in place then the results won’t be nearly as good. zxfer would still be useful to reliably and easily copy a pool for example, but you would be missing the main point of the program.


Common options are listed, followed by options as they function specifically with zfs(8) send mode, followed by options as they work specifically to rsync(1) aka -S mode.

Please note that options with arguments (e.g. -R, -N and the like) can not be concatenated after other options. (e.g. -vFdR source destination will fail. You should use instead: -vFd -R source destination ) Otherwise this will confuse getopts and zfs(8) will complain that "dataset already exists".

The options are as follows:
-b Small (b)eep mode. Play a failure tune before exit with failure so that you don’t have to monitor the terminal to know when a lengthy backup or restore finishes. (This is not as yet supported in (Open) Solaris.) To save insult being added to injury, the failure beep will not play during errors that zxfer discovers in the initialization phase, beeps will only occur if an error has the possibility of occurring after significant time has elapsed.

-B Large (B)eep mode. Similar to (b) but suitable for use at the end of a script. It plays a success or failure tune before exit. If you are executing zxfer multiple times, use -b for everything but the last execution, for which you should use -B.
-e R(e)store property mode. This restores all filesystem properties from the backup file mentioned in the previous option.

A word of warning: In order to allow the restoration of filesystems within the hierarchy, zxfer will begin at the level you specify, and traverse the filesystem hierarchy back to the pool level until it finds an appropriate .zxfer_backup_info file or fails. It will use the first such file it comes across, so be careful about backing up from multiple individual levels of the same filesystem hierarchy.

-h Prints (h)elp.
-k Bac(k)up property mode. This backs up the original filesystem property settings to a file .zxfer_backup_info.<pool_name>. This file is located in the directory that is the mountpoint of the parent filesystem that will contain the root filesystem you are sending. e.g. if you are backing up zroot to be located as per storage/backups/zroot/... the file /storage/backups/.zxfer_backup_info.zroot would hold all the information about the original values of the filesystem properties, and some other useful info.

This allows us to use the [-o] option freely, e.g. specifying copies, compression etc. without having to remember what the original options were.

A word of warning: if you intend to backup to one location and further backup that backup to another location - sourcing the properties to use in the final backup property file from the property backup file in the intermediate backup is not yet supported. A workaround is to refrain from using property overrides in the intermediate backup; this will mean that the ultimate backup will be able to store the correct properties of the original.

-n Dry ru(n) mode. Prints out the commands that would otherwise execute but does not execute them. This may not work in all circumstances as it may expect the existence of filesystems etc. that won’t be created.
-o (o)verride property mode. Property overrides are specified with commas to separate.

e.g. -o property1=value1,property2=value2... For example, -o compression=lzjb will cause all destination filesystems to be set to lzjb compression. If using recursive mode, only the root filesystem will be set, and all other filesystems will inherit from this. Note that this option will also override any values that would otherwise be set by "-P". Invoking this option will also create the destination filesystem(s) if they do not already exist.

-P Transfer (P)roperty mode. This causes the destination to have properties explicitly set (i.e. with property sources as local) to exactly the same properties as the source. If the destination filesystems do not exist, they will be created with the correct properties.

If using recursive modes, child filesystems have property sources (as in, the fourth column of # zfs get all pool/filesystem ) that are made either local, (if the source is local) or inherited (if the source is default or inherited) as per the source filesystem. Note that inherited behaves in a similar manner to default. If you were to set a given property of the parent of a child filesystem, the child would have that same property’s source listed as "inherited from..." whether that child property source had been default or inherited.

There are several properties that must be set (using zfs create) at filesystem creation time. These are: casesensitivity, normalization, jailed, utf8only. If you are trying to replicate such a filesystem where one of these properties is different from source to destination, destroy the destination filesystems before you begin otherwise the utility will fail with an error.

There are several other properties that may not be technically readonly but it was judged that it would not make sense to try and transfer them. They are: type, creation, used, available, referenced, compressratio, mounted, version, primarycache, secondarycache, usedbysnapshots, usedbydataset, usedbychildren, usedbyrefreservation, version, volsize, mountpoint. There are several properties in FreeBSD 8.2 that are not supported and hence will not be transferred via zxfer, they are: idevices, aclmode, aclinherit, nbmand, shareiscsi, vscan, xattr. If using -S, all filesystems in the pools containing the source directories/files will be created on the destination if they aren’t in existence already, whether they are to hold files/directories or not.

-S rsync(1) mode. If -S is specified, rsync(1) mode is triggered. If -S is absent, zfs(8) send mode is in effect. Several options have different effects depending on whether -S is present or not. Consult the relevant option section before using.

It is also possible to transfer to readonly destination filesystems, but this is only supported if either [-o] or [-P] is enabled.

-v (v)erbose mode.

    Normal | zfs send/receive mode

(i.e. -S is absent)
-c A space delimited list of SMF services in quotes to be temporarily disabled before unmounting the source, then re-enable after changing the mountpoint of the destination. Requires -m.
-d (d)elete snapshots on the destination that are absent on the source. This may be necessary to function properly anyway, in a similar fashion to
-D zxfer will pipe zfs(8) send through the indicated command and parameters, to create a progress bar. A number of macros will be replaced with values before the command is executed:
  Will be replaced with the estimated size of the snapshot.
  Will be replaced with the name of the source dataset@snapshot.


zxfer -O user@host-D ’bar -s %%size%%’-R source destination [-F]. This will occur if you are using zxfer for routine backups and in the interim, culling snapshots on the source. The snapshot corresponding to the most recent snapshot on the destination often gets deleted on the source. Any snapshots on the destination more recent than the most recent common snapshot must be deleted for zfs send to work.
-g (g)randfather protection. Specify a number of days old (relative to the system date) at and above which snapshots on the destination won’t be deleted. For use with [-d]. This allows a safeguard to protect the "grandfathers" in a Grandfather-Father-Son (GFS) snapshot collection on a destination. Grandfathers (as defined by zxfer) are the snapshots that never get deleted (often yearly, half yearly or quarterly snapshots).

Note that for this to work properly, you must set [-g] so that it does not inadvertently protect the "fathers" which will be deleted on the source by your snapshot management tool, and hence will need to be deleted on the destination. If you go a long time between backups with an otherwise well set [-g], you may have fathers on the destination that are the age of grandfathers and so you will need to either relax the number of days provided for, or manually delete those fathers.

For example, specifying -g 375 should protect snapshots as old or older than 375 days, which could be useful where grandfathers are yearly and monthly fathers are kept for a period of a year or less. This gives us 9 days of grace period to make a backup without throwing an error, but do note that during this grace period grandfathers less than 375 days old are not protected.

-I properties,to,ignore
  Do not copy this comma separated list of properties when performing replication. Useful for skipping properties like quotas that can interfere with replication, or properties that are not supported on the destination.
-m After sending all snapshots, (m)igrate the source to the destination filesystem by unmounting the source filesystem and changing the new filesystem’s mountpoint to that of the source. This option includes -s. It also includes -P. Note that zxfer does not prevent you from migrating a default mountpoint (e.g. pool/filesystem) to something that will be potentially confusing, so be sure that this is what you want before executing.

Note also that [-O] and [-T] (i.e. remote transfers) are not supported with this option enabled.

-N Replicate the listed filesystem. Note the provisos listed above in [-R]. It works similarly but is (N)ot recursive. e.g. specifying -N tank/tmp will transfer only tank/tmp.
-O Specify an (O)rigin user@host. This allows transfers FROM a remote host via ssh. e.g. Whatever filesystems you specify as the source are taken to exist on that remote host.

For this to work, you must have a working ssh connection from your local machine to the remote host, using public key based authentication (so that you won’t have to keep entering a password every time a command is sent over ssh). You must have zxfer on your local machine. The remote host must support zfs(1), and so does your local machine if [-T] is not also used.

This option has been somewhat tested in FreeBSD 8.2 and Solaris 11 Express and appears to be working. (Consider it alpha level.) These are the only operating systems that it has been tested on, and possibly/probably won’t work on others.

Note also that transferring between different operating systems and even different versions of the same operating system (e.g. FreeBSD 8.1 and 8.2) has not been tested and will probably fail or give unexpected results. As zfs(1), has been developed, new properties have come into being, and those properties have either been supported in FreeBSD or they haven’t. So it is difficult to know what a user would like to have such properties be when they are copied from one OS (or version) to another. At least between OS versions, you are advised to use the same OS and zpool and zfs version from source to destination. It’s not likely I will test this thoroughly in the near future, as it requires an estimated n^2 number of tested transfers, where n is the number of operating system variations to support. You are welcome to try it though, and report bugs back to me.

Note that if at all possible, do not try and be clever and run zxfer with both an origin and a target host. While this may work, the transfer will be piped from the remote origin to the local machine and from there to the remote target machine, which will be slow as it is not a direct path.

The syntax for this command is -O user@remote_host.

e.g. -O root@

Please note that if you are using Solaris, you will most likely need to use "pfexec" (similar to sudo) and have a suitably privileged user. Copy the quotes and spacing exactly:

e.g. -O "user1@ pfexec"

The reason this works is because the commands that are related to reading/writing/modifying data will be prefaced with in normal circumstances:

ssh root@ command ...

So with Solaris, specifying the pfexec at the end results in:

ssh user1@ pfexec command ...

-R (R)ecursively replicate all filesystems under the specified source. If not specifying [-S], you must invoke one and only one of either [-R] or [-N]. Note that if you enable this option, you must specify only one filesystem, and that it starts without a "/". e.g. specifying -R tank/tmp will transfer tank/tmp, tank/tmp/foo, tank/tmp/foo/bar etc.

Also note that a trailing slash on the source filesystem has a similar effect as it has in cp(1). This would primarily be used in restoring filesystems, especially pools. See Ex3.

-s Make a (s)napshot of the source before replication. Note that you might want to transfer a current snapshot at the end of a transfer, as the initial transfer might take a long time. This would leave you with an old snapshot on the destination. To do this you will need to execute your command again at the end, and ensure that a current snapshot is taken before or during the second execution. e.g. use this option to ensure that a relatively current snapshot exists, create it manually, or wait until your own snapshotting regime does the job for you (if you have one).
-T Specify a (T)arget user@host. This allows transfers TO a remote host via ssh. e.g. Whatever filesystem you specify as the destination will be where the source filesystems will be sent.

See the section on [-O] for notes, usage advice and warnings, as this option is very similar in operation.

The syntax for this command is -T user@remote_host. e.g. -T root@

Again, please note that if you are using Solaris, you will most likely need to use "pfexec" (similar to sudo) and have a suitably privileged user. Copy the quotes and spacing exactly:

e.g. -T "user1@ pfexec"

-U Skip replicating any properties that are not supported by the destination. Before replication begins, a list of supported properties is fetched from the destination and any properties not on that list are removed from the list of properties to be replicated. This allows replicating from newer versions of OpenZFS to older versions.

    Rsync mode

(i.e. -S is specified)
-d (d)elete files on the destination that do not exist on the source. This is equivalent to rsync --del.
-E Pass (E)xclude patterns to rsync(1). e.g. If you want to specify "--exclude=/boot/zfs/zpool.cache" when rsync(1) is called, then use "-E /boot/zfs/zpool.cache". You can specify this option as many times as you like, and it will pass each exclude pattern to rsync(1). My understanding of how to get this to work is to specify the exclude as a continuation of the filesystem mountpoint on which the file/directory is stored. e.g. with "/boot/zfs/zpool.cache" it works because the mountpoint of zroot is effectively "/".
-f Specify a (f)ile that contains a list of options to feed to rsync. In this event, no other options will be given to rsync. (If this option is not enabled, the default options given to rsync are -clptgoD --inplace --relative -H --numeric-ids. )

It has been suggested that it might be more convenient to be able to specify custom options to rsync by means of a switch and the options in quotes or some other delimiting character. If there is enough feedback I will consider implementing this option.

-i (i)nclude directories corresponding to ZFS filesystem mountpoints on the destination when transferring. The default is to exclude them, since the destination may correspond to a filesystem from another pool mounted there, which has its own data and would be restored independently.
-l Treat (l)egacy mountpoints as being equal to "/". If this is not enabled, zxfer will fail with an error when it encounters a legacy mountpoint.
-L Specify how many (L)evels deep in the source filesystem tree the filesystem that was originally a backed up pool now lies. Most likely, this will only need to be used in the event of a restore, as the default level (zero) will create filesystems from the pool level on down at the target. e.g. if we are trying to restore /storage/backups/zroot/tmp/stuff.txt which was originally in a pool named zroot, and wished it to end up where it originally came from (e.g. at zroot/tmp/stuff.txt ) we would indicate with -L 2 that the original pool is located 2 levels deep on the source. If we did not specify that option, we would end up with the file transferred to /zroot/backups/zroot/tmp/stuff.txt, which is not what is wanted.
-N Replicate the listed director(y | ies) or file(s). Note the provisos listed above in [-R]. It works similarly but is not recursive. e.g. specifying -N /tmp will transfer only /tmp.
-p (p)ersist through rsync(1) errors. This saves having to feed directories individually to zxfer, if we expect rsync to return an error at some point (e.g. when it tries to overwrite itself).
-R (R)ecursively replicate all directories and files under the specified source(s). If specifying [-S], you must invoke at least one or both of either [-R] or [-N]. The idea is that this utility makes an atomic clone of the filesystems you will need to get your files/directories from, and you can use rsync to decide what to transfer within a given pool.

Note that if you enable this option, you can specify as many directories as you like, separated by commas (with no spaces). Directories must start with a / and may or may not end with a /. Read the rsync(1) man page to get the gist of how that works. e.g. specifying -R /tmp will transfer /tmp, /tmp/foo, /tmp/foo/bar etc.

Note also that zxfer will only transfer the contents of the directory "/" if [-l] is invoked, "/" is mounted as legacy, and it will only transfer across those files and directories belonging to the same ZFS filesystem as / belongs to.

Another action not supported is recursively transferring a directory that contains directories that are in fact filesystems from other pools, or in fact any included directories where the filesystem mountpoints diverge from what ZFS would assign by default.

-u (u)se an already existing snapshot as the source to transfer from. You should first check that this snapshot exists on all the filesystems that house the files and directories to be used in the transfer. This gives us the option of restoring files/directories without having to roll back.


Note that some of these example commands are lengthy, so be sure to fix the line wrapping appropriately. Also if you wonder why zxfer isn’t transferring anything, please read the section titled SNAPSHOTS.

    Ex1 - Backup a pool (including snapshots and properties)

We have a pool called storage and we want to back it up to backup01/pools, along with all its snapshots. Grandfather snapshots are yearly, fathers are monthly and are deleted after 365 days. The resultant filesystem hierarchy should look like so:
  • backup01/pools/storage
  • backup01/pools/storage/home
  • backup01/pools/storage/back
  • etc.
To back this up while:
  • [-g] protecting (grandfather) snapshots older than 375 days
  • [-P] copying across the properties of each filesystem
  • [-k] storing the original filesystem properties in the file backup01/pools/
  • [-F] forcing a rollback of destination to the most recent snapshot. Given even mounting the filesystem will cause a change and hence cause zfs receive to fail with an error, enabling this is the way to go. Otherwise you would be modifying(!) a backup, wanting to keep the changes you are making(!?) and also wanting to copy more stuff to the backup (hence it’s still being used as a backup)... well if that’s what you want then don’t use this option.
  • [-d] deleting stale snapshots that don’t exist on the source (e.g. if using a snapshot management script such as zfs-snapshot-mgmt(8), snapshots are regularly taken and regularly deleted to leave a range of frequencies of snapshots at different vintages. If you are regularly backing up to another pool which is stored off-site as is highly recommended, you may want to delete the stale snapshots on the backup pool without having to manage the snapshots there too. This is especially true for those pools that are usually not connected to a machine, e.g. if you are using HDD as backup media. Note that zfs send will also refuse to work if you have newer snapshots on destination than the most recent common snapshot on both, so it’s easier to just enable it.)
  • [-v] seeing lots of output (verbose)
  • [-R] copying the source filesystem recursively
use the following command:

zxfer -dFkPv -g 376 -R storage backup01/pools

Note that this same command will work for both the initial replication and subsequent replications (which are potentially much faster due to incremental transfers being used). Also note that if you don’t have any snapshots on the source, nothing will be transferred. You can create a snapshot for this very occasion by adding the -s option.

    Ex2 - Backup pool to HDD

Using HDDs as backup media was in large part a motivation for writing this utility. (Using an e-SATA dock is particularly convenient). The source and destination are the same as Ex1.

We will want to increase the number of copies to at least 2 or more so that we have some protection against bad sectors. We won’t have protection against a HDD crash so use more than one HDD if you are doing this (mirrored or otherwise). We may also want to override the compression to make up for the multiplication in disk usage by the number of copies. Here is the command:

zxfer -dFkPv -o copies=2,compression=lzjb -R storage backup01/pools

    Ex3 - Restore a pool

To restore the pools we have backed up in Examples 1 and 2, we would first make sure that there is a new pool named storage to copy the backup to. Then we would issue the following command:

zxfer -deFPv -R backup01/pools/storage/ storage

Note that the trailing slash enables us to copy the zroot filesystem directly to the pool level, and then the child filesystems below that, which is where we want them. If the pool name is to be changed, the command becomes:

zxfer -deFPv -R backup01/pools/storage/ newpoolname

    Ex4 - Backup a filesystem

We might want to just backup a filesystem within a pool. That is easily done:

zxfer -dFkPv -N storage/home backup01/filesystems

The resulting filesystem will be backup01/filesystems/home. This example will only replicate that exact filesystem (i.e. it is non-recursive). If we wanted to recursively transfer all filesystems under storage/home at the same time we could do so by changing the [-N] to an [-R].

    Ex5 - Restore a filesystem

To restore the filesystem backed up in Ex4, we would do so using the following command:

zxfer -deFPv -N backup01/filesystem/home storage

    Ex6 - Recursive directory backup

We might want to backup a directory within a pool, using rsync to do the heavy lifting, while also making a backup of the properties of the filesystems transferred. Transferring via [-S] will allow us to have different snapshotting regimes on source and destination coexisting happily.

zxfer -SkPv -R /storage/home backup01/rsbacks

The resulting filesystem structure will look like: backup01/rsbacks/storage/home.

If we wanted to non-recursively transfer that directory we would just change the [-R] to an [-N].

    Ex7 - Recursive directory restore

To restore the directory backed up in Ex6, we would do so using the following command:

zxfer -SePv -L 2 -N /backup01/rsbacks/storage/home storage

Note that we had to specify a drop back of 2 levels of filesystems, so that zxfer would know that the pool level is not backup01 but storage. Specifying -L of 1 would indicate that the pool level was rsbacks, which it was not. Leaving out [-L] would be equivalent to L=0, or specifying that the pool level was backup01.

Note also that this will re-create all the original filesystems that existed on the pool "storage" with their original properties, if they have since been deleted. If those filesystems still exist, zxfer will ensure that each such filesystem have the properties they originally had. Note that if those filesystems still exist, no data will be changed other than what you have specified to be rsynced across.

If you wish to not have filesystems created or properties set (just the files/directories you want rsynced), just forego [-P] and [-o]. Note that this will only work on filesystems that are writable.

    Ex8 - Backup FreeBSD 8.2 root mirror

This will make a recursive snapshot of the root mirror, create similar filesystems on the pool storage, transfer the properties over, rsync(1) across the directories and files needed to restore the system, and destroy the snapshots when done. To see how to do this in more detail, check out the zxfer wiki.

zxfer -SPkld -R /bin,/boot,/compat,/etc,/lib,/libexec,/rescue,/root,/sbin,/tmp,/usr,/var,/vshare -N /.cshrc,/.profile storage/zr_backup

The resulting filesystem structure will look something like: storage/zr_backup/zroot storage/zr_backup/zroot/usr storage/zr_backup/zroot/var etc.

    Ex9 - Restore FreeBSD 8.2 root mirror

To restore the config files backed up in Ex8, we would do so using the following command after installing the system, installing zxfer and booting up in the system. This uses the snapshot auto-2010-11-14_14.00. Note that for this to work properly /var/empty must be set to mutable. Also, the flag "schg" must be turned off to transfer properly. For the full sequence of commands, see the zxfer wiki. Here is the command for the zxfer part of the procedure (note you will need to add any directories of your creation kept on your zroot e.g. "vshare"):

zxfer -SpldBv -E /boot/zfs/zpool.cache -u auto-2010-11-14_14.00 -L 2 -N $zrootdir/.cshrc,$zrootdir/.profile -R $zrootdir/bin,$zrootdir/boot,$zrootdir/compat,$zrootdir/etc,$zrootdir/lib,$zrootdir/libexec,$zrootdir/rescue,$zrootdir/root,$zrootdir/sbin,$zrootdir/tmp,$zrootdir/usr,$zrootdir/var,$zrootdir/vshare zroot

    Ex10 - Migrate a filesystem

We might want to migrate a filesystem (including properties). Note that this is only allowable when the original mountpoint is not the default (i.e. pool/filesystem). In the following example, the new filesystem will be located in new_pool/location/fs. If the old mountpoint was /path/to/old_fs then that will be the mountpoint of the new filesystem.

zxfer -PmFdv -N original_pool/fs new_pool/location

    Ex11 - Compress a filesystem

If we want to compress a filesystem, it is not enough to simply set a compression setting of some sort on that filesystem. This will only cause new files to be compressed. If we want to compress a filesystem, what we would want to do is to transfer it to another location (where compression is enabled).

zxfer -PmFdv -o compression=gzip -N original_pool/fs new_pool/location

    Ex12 - Compress a filesystem...

- and store it in the original location. This is probably what you want to do instead of example 11. Usually what we want to do when we want to compress a filesystem - it is already in the location we want it to be, just we haven’t realized we wanted it compressed at the time. Or maybe we want to do something similar to compression, like dedup, and it was not supported at the time we created the filesystem. So it is not enough to have the filesystem compressed in a new location, we want it in the original location.

If so, we will need to migrate the filesystem. Then, if necessary, we would need to upgrade the original pool to ensure that the new filesystem can do what it is we want it to do (e.g. dedup perhaps), and then transfer it back. Here are the steps.

1. Ensure you have set aside a time where nothing will be reading or writing to the filesystem(s) in question. If you are performing this operation on a system filesystem (e.g. something like zroot/usr) then ensure that you are performing these operations from a recovery disk (e.g. Fixit # in FreeBSD). Also it is a very good idea to ensure that you have made backups of the filesystems you are going to perform this operation on.

2. Migrate the filesystems to a new location. e.g.

zxfer -PmFdv -N original_pool/fs new_pool/location

3. Triple check that the new filesystems are as they should be. Be very, very, very careful here. It is a good idea to have made a backup before doing this next step. In fact, it’s probably worth practicing on a system you don’t care about first. And do not, repeat do not, blame me if something goes wrong.

4. Destroy the original filesystem. e.g.

zfs destroy original_pool/fs

5. Ensure that the original pool is upgraded to do what you want it to do (e.g. dedup perhaps, though you will need to change the option setting appropriately).

6. Migrate the filesystem back, but with the overrides you want. e.g.

zxfer -PmFdv -o compression=gzip -N new_pool/location/fs original_pool

    Ex13 - Backup a pool to a remote host

Notice this is the same as in Ex2 with the exception of option [-T], and uses the same options which have been explained in that example. Note that if you use Solaris you will most likely need to specify pfexec (refer to the [-O] section). Here is the command:

zxfer -dFkPv -o copies=2,compression=lzjb -T root@ -R storage backup01/pools

    Ex14 - Restore a pool from a remote host

Use the following command, assuming that you are restoring from a situation as in Ex13. Again, if using Solaris refer to [-O].

zxfer -deFPv -O root@ -R backup01/pools/storage/ storage


zxfer exits 0 on success, 1 on an error and 2 if a command line option is incorrect.


rsync(1), zfs(1), zpool(1)


zxfer is tested (somewhat) before release on FreeBSD 8.2-RELEASE and Solaris Express 11. It was tested on the last version of OpenSolaris and FreeBSD 8.1 as of 0.9.0 and may continue to function correctly, but in order to ease my workload I am only going to test zxfer against Solaris Express 11 and whatever version I run of FreeBSD, in my case 8.2.


Thanks to Constantin Gonzalez for his constant collaboration, guidance, and his providing of a sounding board for ideas and decisions as I developed this script. It is no understatement to say that this script would not have been developed to the extent it has and in its present form if not for his encouragement, input on design decisions, and often just simply agreeing that some features would be really cool, which spurred me on.

Constantin’s zfs-replicate script formed the original basis for this one, and was very useful as a template for me to follow. Thanks to Constantin also for generously allowing his code to be licensed under the BSD license, and also encouraging the existence of this project under its own banner.

You can read Constantin’s blog "Constant Thinking" at - if you are at all interested in the world of ZFS it is worth reading regularly (his non-ZFS stuff is good too).

Thanks also to the creators of rsync for their excellent tool.


The basis for zxfer, zfs-replicate, was written by Constantin Gonzalez. Ivan Nash Dreckman built upon that work to create the additional code and documentation required for zxfer. Constantin was invaluable throughout with providing feedback on design decisions, suggestions and encouragement, not to mention initial testing on Solaris.


(This is a bug of ZFS on FreeBSD and not this script.) There are several properties in FreeBSD that when set via "zfs create" or "zfs set" will have the source stay as default while others are set to local. This does not have any real impacts because these properties are not inheritable. The properties are: quota, reservation, canmount, refquota, refreservation.

Note that FreeBSD does not support the transfer of several properties. See [-P] section for details on this.

There are several properties that are skipped over when transferring or setting properties - search the script for "readonly_properties" to see what they are. If you find that certain newer ZFS properties are not being transferred, there is a good chance that those properties they have been added to this list. That is because testing has indicated that attempting to create with or set those properties would cause the script to fail. If you can make a good case that the script should heed those property values, feel free to email me.

Send bug reports to ivannashdreckman at fastmailgolf dot fm, but not before removing the sport originating in Scotland from the email address. If you like zxfer and find it useful, send some feedback saying how you use it, and consider donating at some stage in the future.


zxfer is distributed under the BSD license. See the file COPYING for details.

The website for zxfer is For additional help, consult the wiki on that site.

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