zfs(8)

NAME
zfs - configures ZFS file systems

SYNOPSIS

zfs [-?]

zfs create [-p] [-o property=value] ... filesystem

zfs create [-ps] [-b blocksize] [-o property=value] ... -V size volume

zfs destroy [-fnpRrv] filesystem|volume

zfs destroy [-dnpRrv] filesystem|volume@snap[%snap][,...]

zfs destroy filesystem|volume#bookmark

zfs snapshot | snap [-r] [-o property=value] ...
      filesystem@snapname|volume@snapname ...

zfs rollback [-rRf] snapshot

zfs clone [-p] [-o property=value] ... snapshot filesystem|volume

zfs promote clone-filesystem

zfs rename [-f] filesystem|volume|snapshot
     filesystem|volume|snapshot

zfs rename [-fp] filesystem|volume filesystem|volume

zfs rename -r snapshot snapshot

zfs list [-r|-d depth][-Hp][-o property[,property]...] [-t type[,type]..]
     [-s property] ... [-S property] ... [filesystem|volume|snapshot|mountpoint] ...

+zfs set property=value... filesystem|volume|snapshot...

zfs get [-r|-d depth][-Hp][-o field[,...]] [-t type[,...]]
    [-s source[,...]] "all" | property[,...] filesystem|volume|snapshot|mountpoint ...

zfs inherit [-rS] property filesystem|volume|snapshot ...

zfs upgrade [-v]

zfs upgrade [-r] [-V version] -a | filesystem

zfs userspace [-Hinp] [-o field[,...]] [-s field] ...
    [-S field] ... [-t type[,...]] filesystem|snapshot

zfs groupspace [-Hinp] [-o field[,...]] [-s field] ...
    [-S field] ... [-t type[,...]] filesystem|snapshot

zfs mount

zfs mount [-vO] [-o options] -a | filesystem

zfs unmount | umount [-f] -a | filesystem|mountpoint

zfs share -a | filesystem

zfs unshare -a filesystem|mountpoint

zfs bookmark snapshot bookmark

zfs send [-DnPpRveLc] [-[iI] snapshot] snapshot

zfs send [-Le] [-i snapshot|bookmark] filesystem|volume|snapshot

zfs send [-Penv] -t receive_resume_token

zfs receive [-Fnsuv] [-o origin=snapshot] filesystem|volume|snapshot

zfs receive [-Fnsuv] [-d|-e] [-o origin=snapshot] filesystem

zfs receive -A filesystem|volume

zfs allow filesystem|volume

zfs allow [-ldug] "everyone"|user|group[,...] perm|@setname[,...]
     filesystem|volume

zfs allow [-ld] -e perm|@setname[,...] filesystem|volume

zfs allow -c perm|@setname[,...] filesystem|volume

zfs allow -s @setname perm|@setname[,...] filesystem|volume

zfs unallow [-rldug] "everyone"|user|group[,...] [perm|@setname[,... ]]
     filesystem|volume

zfs unallow [-rld] -e [perm|@setname[,... ]] filesystem|volume

zfs unallow [-r] -c [perm|@setname[ ... ]] filesystem|volume

zfs unallow [-r] -s @setname [perm|@setname[,... ]] filesystem|volume

zfs hold [-r] tag snapshot...

zfs holds [-r] snapshot...

zfs release [-r] tag snapshot...

zfs diff [-FHt] snapshot snapshot|filesystem

DESCRIPTION

The zfs command configures ZFS datasets within a ZFS storage pool, as described in zpool(8). A dataset is identified by a unique path within the ZFS namespace. For example:

pool/{filesystem,volume,snapshot}

where the maximum length of a dataset name is MAXNAMELEN (256 bytes).

A dataset can be one of the following:

filesystem

    A ZFS dataset of type filesystem can be mounted within the standard system namespace and behaves like other file systems. While ZFS file systems are designed to be POSIX compliant, known issues exist that prevent compliance in some cases. Applications that depend on standards conformance might fail due to nonstandard behavior when checking file system free space.

volume

    A logical volume exported as a raw or block device. This type of dataset should only be used under special circumstances. File systems are typically used in most environments.

snapshot

    A read-only version of a file system or volume at a given point in time. It is specified as filesystem@name or volume@name.

bookmark

    Much like a snapshot, but without the hold on on-disk data. It can be used as the source of a send (but not for a receive). It is specified as filesystem#name or volume#name.

  ZFS File System Hierarchy

A ZFS storage pool is a logical collection of devices that provide space for datasets. A storage pool is also the root of the ZFS file system hierarchy.

The root of the pool can be accessed as a file system, such as mounting and unmounting, taking snapshots, and setting properties. The physical storage characteristics, however, are managed by the zpool(8) command.

See zpool(8) for more information on creating and administering pools.

  Snapshots

A snapshot is a read-only copy of a file system or volume. Snapshots can be created extremely quickly, and initially consume no additional space within the pool. As data within the active dataset changes, the snapshot consumes more data than would otherwise be shared with the active dataset.

Snapshots can have arbitrary names. Snapshots of volumes can be cloned or rolled back. Visibility is determined by the snapdev property of the parent volume.

File system snapshots can be accessed under the .zfs/snapshot directory in the root of the file system. Snapshots are automatically mounted on demand and may be unmounted at regular intervals. The visibility of the .zfs directory can be controlled by the snapdir property.

  Bookmarks

A bookmark is like a snapshot, a read-only copy of a file system or volume. Bookmarks can be created extremely quickly, compared to snapshots, and they consume no additional space within the pool. Bookmarks can also have arbitrary names, much like snapshots.

Unlike snapshots, bookmarks can not be accessed through the filesystem in any way. From a storage standpoint a bookmark just provides a way to reference when a snapshot was created as a distinct object. Bookmarks are initially tied to a snapshot, not the filesystem/volume, and they will survive if the snapshot itself is destroyed. Since they are very light weight there's little incentive to destroy them.

  Clones

A clone is a writable volume or file system whose initial contents are the same as another dataset. As with snapshots, creating a clone is nearly instantaneous, and initially consumes no additional space.

Clones can only be created from a snapshot. When a snapshot is cloned, it creates an implicit dependency between the parent and child. Even though the clone is created somewhere else in the dataset hierarchy, the original snapshot cannot be destroyed as long as a clone exists. The origin property exposes this dependency, and the destroy command lists any such dependencies, if they exist.

The clone parent-child dependency relationship can be reversed by using the promote subcommand. This causes the "origin" file system to become a clone of the specified file system, which makes it possible to destroy the file system that the clone was created from.

  Mount Points

Creating a ZFS file system is a simple operation, so the number of file systems per system is likely to be numerous. To cope with this, ZFS automatically manages mounting and unmounting file systems without the need to edit the /etc/fstab file. All automatically managed file systems are mounted by ZFS at boot time.

By default, file systems are mounted under /path, where path is the name of the file system in the ZFS namespace. Directories are created and destroyed as needed.

A file system can also have a mount point set in the mountpoint property. This directory is created as needed, and ZFS automatically mounts the file system when the zfs mount -a command is invoked (without editing /etc/fstab). The mountpoint property can be inherited, so if pool/home has a mount point of /export/stuff, then pool/home/user automatically inherits a mount point of /export/stuff/user.

A file system mountpoint property of none prevents the file system from being mounted.

If needed, ZFS file systems can also be managed with traditional tools (mount, umount, /etc/fstab). If a file system's mount point is set to legacy, ZFS makes no attempt to manage the file system, and the administrator is responsible for mounting and unmounting the file system.

  Deduplication

Deduplication is the process for removing redundant data at the block-level, reducing the total amount of data stored. If a file system has the dedup property enabled, duplicate data blocks are removed synchronously. The result is that only unique data is stored and common components are shared among files.

WARNING: DO NOT ENABLE DEDUPLICATION UNLESS YOU NEED IT AND KNOW EXACTLY WHAT YOU ARE DOING!

Deduplicating data is a very resource-intensive operation. It is generally recommended that you have at least 1.25 GiB of RAM per 1 TiB of storage when you enable deduplication. But calculating the exact requirements is a somewhat complicated affair.

Enabling deduplication on an improperly-designed system will result in extreme performance issues (extremely slow filesystem and snapshot deletions etc.) and can potentially lead to data loss (i.e. unimportable pool due to memory exhaustion) if your system is not built for this purpose. Deduplication affects the processing power (CPU), disks (and the controller) as well as primary (real) memory.

Before creating a pool with deduplication enabled, ensure that you have planned your hardware requirements appropriately and implemented appropriate recovery practices, such as regular backups.

Unless necessary, deduplication should NOT be enabled on a system. Instead, consider using compression=lz4, as a less resource-intensive alternative.

  Properties

Properties are divided into two types: native properties and user-defined (or "user") properties. Native properties either export internal statistics or control ZFS behavior. User properties have no effect on ZFS behavior, but you can use them to annotate datasets and snapshots in a way that is meaningful in your environment.

Properties are generally inherited from the parent unless overridden by the child. See the documentation below for exceptions.

  Native Properties
Native properties apply to all dataset types unless otherwise noted. However, native properties cannot be edited on snapshots.

The values of numeric native properties can be specified using human-readable abbreviations (K, M, G, T, P, E, and Z). These abbreviations can optionally use the IEC binary prefixes (e.g. GiB) or SI decimal prefixes (e.g. GB), though the SI prefixes are treated as binary prefixes. Abbreviations are case-insensitive. The following are all valid (and equal) specifications:

1536M, 1.5g, 1.50GB, 1.5GiB

The values of non-numeric native properties are case-sensitive and must be lowercase, except for mountpoint, sharenfs, and sharesmb.

The following native properties consist of read-only statistics about the dataset. These properties can be neither set, nor inherited.

available

    The amount of space available to the dataset and all its children, assuming that there is no other activity in the pool. Because space is shared within a pool, availability can be limited by any number of factors, including physical pool size, quotas, reservations, or other datasets within the pool.

    This property can also be referred to by its shortened column name, avail.

compressratio

    For non-snapshots, the compression ratio achieved for the used space of this dataset, expressed as a multiplier. The used property includes descendant datasets, and, for clones, does not include the space shared with the origin snapshot. For snapshots, the compressratio is the same as the refcompressratio property. The compression property controls whether compression is enabled on a dataset.

creation

    The time this dataset was created.

clones

    For snapshots, this property is a comma-separated list of filesystems or volumes which are clones of this snapshot. The clones' origin property is this snapshot. If the clones property is not empty, then this snapshot can not be destroyed (even with the -r or -f options). The roles of origin and clone can be swapped by promoting the clone with the zfs promote command.

defer_destroy

    This property is on if the snapshot has been marked for deferred destruction by using the zfs destroy -d command. Otherwise, the property is off.

filesystem_count

    The total number of filesystems and volumes that exist under this location in the dataset tree. This value is only available when a filesystem_limit has been set somewhere in the tree under which the dataset resides.

logicalreferenced

    The amount of space that is "logically" accessible by this dataset. See the referenced property. The logical space ignores the effect of the compression and copies properties, giving a quantity closer to the amount of data that applications see. However, it does include space consumed by metadata.

    This property can also be referred to by its shortened column name, lrefer.

logicalused

    The amount of space that is "logically" consumed by this dataset and all its descendents. See the used property. The logical space ignores the effect of the compression and copies properties, giving a quantity closer to the amount of data that applications see. However, it does include space consumed by metadata.

    This property can also be referred to by its shortened column name, lused.

mounted

    For file systems, indicates whether the file system is currently mounted. This property can be either yes or no.

origin

    For cloned file systems or volumes, the snapshot from which the clone was created. The origin cannot be destroyed (even with the -r or -f options) so long as a clone exists. See also the clones property.

receive_resume_token

    For filesystems or volumes which have saved partially-completed state from zfs receive -s , this opaque token can be provided to zfs send -t to resume and complete the zfs receive.

referenced

    The amount of data that is accessible by this dataset, which may or may not be shared with other datasets in the pool. When a snapshot or clone is created, it initially references the same amount of space as the file system or snapshot it was created from, since its contents are identical.

    This property can also be referred to by its shortened column name, refer.

refcompressratio

    The compression ratio achieved for the referenced space of this dataset, expressed as a multiplier. See also the compressratio property.

snapshot_count

    The total number of snapshots that exist under this location in the dataset tree. This value is only available when a snapshot_limit has been set somewhere in the tree under which the dataset resides.

type

    The type of dataset: filesystem, volume, or snapshot.

used

    The amount of space consumed by this dataset and all its descendents. This is the value that is checked against this dataset's quota and reservation. The space used does not include this dataset's reservation, but does take into account the reservations of any descendent datasets. The amount of space that a dataset consumes from its parent, as well as the amount of space that are freed if this dataset is recursively destroyed, is the greater of its space used and its reservation.

    When snapshots (see the "Snapshots" section) are created, their space is initially shared between the snapshot and the file system, and possibly with previous snapshots. As the file system changes, space that was previously shared becomes unique to the snapshot, and counted in the snapshot's space used. Additionally, deleting snapshots can increase the amount of space unique to (and used by) other snapshots.

    The amount of space used, available, or referenced does not take into account pending changes. Pending changes are generally accounted for within a few seconds. Committing a change to a disk using fsync(2) or O_SYNC (see open(2)) does not necessarily guarantee that the space usage information is updated immediately.

usedby*

    The usedby* properties decompose the used properties into the various reasons that space is used. Specifically, used = usedbychildren + usedbydataset + usedbyrefreservation + usedbysnapshots. These properties are only available for datasets created on zpool version 13 or higher pools.

usedbychildren

    The amount of space used by children of this dataset, which would be freed if all the dataset's children were destroyed.

usedbydataset

    The amount of space used by this dataset itself, which would be freed if the dataset were destroyed (after first removing any refreservation and destroying any necessary snapshots or descendents).

usedbyrefreservation

    The amount of space used by a refreservation set on this dataset, which would be freed if the refreservation was removed.

usedbysnapshots

    The amount of space consumed by snapshots of this dataset. In particular, it is the amount of space that would be freed if all of this dataset's snapshots were destroyed. Note that this is not simply the sum of the snapshots' used properties because space can be shared by multiple snapshots.

userobjused@user
userused@user

    The amount of space consumed by the specified user in this dataset. Space is charged to the owner of each file, as displayed by ls -l. The amount of space charged is displayed by du and ls -s. See the zfs userspace subcommand for more information.

    Unprivileged users can access only their own space usage. The root user, or a user who has been granted the userused privilege with zfs allow, can access everyone's usage.

    The userused@... properties are not displayed by zfs get all. The user's name must be appended after the @ symbol, using one of the following forms:

        o   POSIX name (for example, joe)

        o   POSIX numeric ID (for example, 789)

        o   SID name (for example, joe.smith@mydomain)

        o   SID numeric ID (for example, S-1-123-456-789)
Files created on Linux always have POSIX owners.
    The userobjused is similar to userused but instead it counts the number of objects consumed by user. This feature doesn't count the internal objects used by ZFS, therefore it may under count a few objects comparing with the results of third-party tool such as dfs -i. When the property xattr=on is set on a fileset, ZFS will create additional objects per-file to store extended attributes. These additional objects are reflected in the userobjused value and are counted against the user's userobjquota. When a filesystem is configured to use xattr=sa no additional internal objects are required.

userrefs

    This property is set to the number of user holds on this snapshot. User holds are set by using the zfs hold command.

groupused@group
groupobjused@group

    The amount of space consumed by the specified group in this dataset. Space is charged to the group of each file, as displayed by ls -l. See the userused@user property for more information.

    Unprivileged users can only access their own groups' space usage. The root user, or a user who has been granted the groupused privilege with zfs allow, can access all groups' usage.
    The groupobjused is similar to groupused but instead it counts the number of objects consumed by group. When the property xattr=on is set on a fileset, ZFS will create additional objects per-file to store extended attributes. These additional objects are reflected in the groupobjused value and are counted against the group's groupobjquota.. When a filesystem is configured to use xattr=sa no additional internal objects are required.

volblocksize=blocksize

    This property, which is only valid on volumes, specifies the block size of the volume. Any power of two from 512B to 128KiB is valid. The default is 8KiB.

    This property cannot be changed after the volume is created.

    This property can also be referred to by its shortened column name, volblock.

written

    The amount of referenced space written to this dataset since the previous snapshot.

written@snapshot

    The amount of referenced space written to this dataset since the specified snapshot. This is the space that is referenced by this dataset but was not referenced by the specified snapshot.

    The snapshot may be specified as a short snapshot name (just the part after the @), in which case it will be interpreted as a snapshot in the same filesystem as this dataset. The snapshot be a full snapshot name (filesystem@snapshot), which for clones may be a snapshot in the origin's filesystem (or the origin of the origin's filesystem, etc).

The following native properties can be used to change the behavior of a ZFS dataset.

aclinherit=restricted | discard | noallow | passthrough | passthrough-x

    Controls how ACL entries are inherited when files and directories are created. A file system with an aclinherit property of discard does not inherit any ACL entries. A file system with an aclinherit property value of noallow only inherits inheritable ACL entries that specify "deny" permissions. The property value restricted (the default) removes the write_acl and write_owner permissions when the ACL entry is inherited. A file system with an aclinherit property value of passthrough inherits all inheritable ACL entries without any modifications made to the ACL entries when they are inherited. A file system with an aclinherit property value of passthrough-x has the same meaning as passthrough, except that the owner@, group@, and everyone@ ACEs inherit the execute permission only if the file creation mode also requests the execute bit.

    When the property value is set to passthrough, files are created with a mode determined by the inheritable ACEs. If no inheritable ACEs exist that affect the mode, then the mode is set in accordance to the requested mode from the application.

    The aclinherit property does not apply to Posix ACLs.

acltype=off | noacl | posixacl

    Controls whether ACLs are enabled and if so what type of ACL to use. When a file system has the acltype property set to off (the default) then ACLs are disabled. Setting the acltype property to posixacl indicates Posix ACLs should be used. Posix ACLs are specific to Linux and are not functional on other platforms. Posix ACLs are stored as an xattr and therefore will not overwrite any existing ZFS/NFSv4 ACLs which may be set. Currently only posixacls are supported on Linux.

    To obtain the best performance when setting posixacl users are strongly encouraged to set the xattr=sa property. This will result in the Posix ACL being stored more efficiently on disk. But as a consequence of this all new xattrs will only be accessible from ZFS implementations which support the xattr=sa property. See the xattr property for more details.

    The value noacl is an alias for off.

atime=on | off

    Controls whether the access time for files is updated when they are read. Setting this property to off avoids producing write traffic when reading files and can result in significant performance gains, though it might confuse mailers and other similar utilities. The default value is on. See also relatime below.

    The values on and off are equivalent to the atime and noatime mount options.

canmount=on | off | noauto

    If this property is set to off, the file system cannot be mounted, and is ignored by zfs mount -a. Setting this property to off is similar to setting the mountpoint property to none, except that the dataset still has a normal mountpoint property, which can be inherited. Setting this property to off allows datasets to be used solely as a mechanism to inherit properties. One example of setting canmount=off is to have two datasets with the same mountpoint, so that the children of both datasets appear in the same directory, but might have different inherited characteristics.

    When the noauto option is set, a dataset can only be mounted and unmounted explicitly. The dataset is not mounted automatically when the dataset is created or imported, nor is it mounted by the zfs mount -a command or unmounted by the zfs unmount -a command.

    This property is not inherited. Every dataset defaults to on independently.

    The values on and noauto are equivalent to the auto and noauto mount options.

checksum=on | off | fletcher2 | fletcher4 | sha256 | noparity | sha512 | skein | edonr

    Controls the checksum used to verify data integrity. The default value is on, which automatically selects an appropriate algorithm (currently, fletcher4, but this may change in future releases). The value off disables integrity checking on user data. The value noparity not only disables integrity but also disables maintaining parity for user data. This setting is used internally by a dump device residing on a RAID-Z pool and should not be used by any other dataset. Disabling checksums is NOT a recommended practice.

    The sha512, skein, and edonr checksum algorithms require enabling the appropriate features on the pool. Please see zpool-features for more information on these algorithms. Changing this property affects only newly-written data.

compression=off | on | lzjb | lz4 | gzip | gzip-N | zle

    Controls the compression algorithm used for this dataset.

    Setting compression to on indicates that the current default compression algorithm should be used. The default balances compression and decompression speed, with compression ratio and is expected to work well on a wide variety of workloads. Unlike all other settings for this property, on does not select a fixed compression type. As new compression algorithms are added to ZFS and enabled on a pool, the default compression algorithm may change. The current default compression algorithm is either lzjb or, if the lz4_compress feature is enabled, lz4.

    The lzjb compression algorithm is optimized for performance while providing decent data compression.

    The lz4 compression algorithm is a high-performance replacement for the lzjb algorithm. It features significantly faster compression and decompression, as well as a moderately higher compression ratio than lzjb, but can only be used on pools with the lz4_compress feature set to enabled. See zpool-features(5) for details on ZFS feature flags and the lz4_compress feature.

    The gzip compression algorithm uses the same compression as the gzip(1) command. You can specify the gzip level by using the value gzip-N where N is an integer from 1 (fastest) to 9 (best compression ratio). Currently, gzip is equivalent to gzip-6 (which is also the default for gzip(1)). The zle compression algorithm compresses runs of zeros.

    This property can also be referred to by its shortened column name compress. Changing this property affects only newly-written data.

copies=1 | 2 | 3

    Controls the number of copies of data stored for this dataset. These copies are in addition to any redundancy provided by the pool, for example, mirroring or RAID-Z. The copies are stored on different disks, if possible. The space used by multiple copies is charged to the associated file and dataset, changing the used property and counting against quotas and reservations.

    Changing this property only affects newly-written data.

    Remember that ZFS will not import a pool with a missing top-level vdev. Do NOT create, for example, a two-disk, striped pool and set copies=2 on some datasets thinking you have setup redundancy for them. When one disk dies, you will not be able to import the pool and will have lost all of your data.

dedup=off | on | verify | sha256[,verify]

    Controls whether deduplication is in effect for a dataset. The default value is off. The default checksum used for deduplication is sha256 (subject to change). When dedup is enabled, the dedup checksum algorithm overrides the checksum property. Setting the value to verify is equivalent to specifying sha256,verify.

    If the property is set to verify, then, whenever two blocks have the same signature, ZFS will do a byte-for-byte comparison with the existing block to ensure that the contents are identical.

    Unless necessary, deduplication should NOT be enabled on a system. See Deduplication above.

devices=on | off

    Controls whether device nodes can be opened on this file system. The default value is on.

    The values on and off are equivalent to the dev and nodev mount options.

dnodesize=legacy | auto | 1k | 2k | 4k | 8k | 16k

    Specifies a compatibility mode or literal value for the size of dnodes in the file system. The default value is legacy. Setting this property to a value other than legacy requires the large_dnode pool feature to be enabled.

    Consider setting dnodesize to auto if the dataset uses the xattr=sa property setting and the workload makes heavy use of extended attributes. This may be applicable to SELinux-enabled systems, Lustre servers, and Samba servers, for example. Literal values are supported for cases where the optimal size is known in advance and for performance testing.

    Leave dnodesize set to legacy if you need to receive a zfs send stream of this dataset on a pool that doesn't enable the large_dnode feature, or if you need to import this pool on a system that doesn't support the large_dnode feature.

    This property can also be referred to by its shortened column name, dnsize.

exec=on | off

    Controls whether processes can be executed from within this file system. The default value is on.

    The values on and off are equivalent to the exec and noexec mount options.

mlslabel=none | label

    The mlslabel property is a sensitivity label that determines if a dataset can be mounted in a zone on a system with Trusted Extensions enabled. If the labeled dataset matches the labeled zone, the dataset can be mounted and accessed from the labeled zone.

    When the mlslabel property is not set, the default value is none. Setting the mlslabel property to none is equivalent to removing the property.

    The mlslabel property can be modified only when Trusted Extensions is enabled and only with appropriate privilege. Rights to modify it cannot be delegated. When changing a label to a higher label or setting the initial dataset label, the {PRIV_FILE_UPGRADE_SL} privilege is required. When changing a label to a lower label or the default (none), the {PRIV_FILE_DOWNGRADE_SL} privilege is required. Changing the dataset to labels other than the default can be done only when the dataset is not mounted. When a dataset with the default label is mounted into a labeled-zone, the mount operation automatically sets the mlslabel property to the label of that zone.

    When Trusted Extensions is not enabled, only datasets with the default label (none) can be mounted.

    Zones are a Solaris feature and are not relevant on Linux.

filesystem_limit=none | count

    Limits the number of filesystems and volumes that can exist under this point in the dataset tree. The limit is not enforced if the user is allowed to change the limit. Setting a filesystem_limit on a descendent of a filesystem that already has a filesystem_limit does not override the ancestor's filesystem_limit, but rather imposes an additional limit. This feature must be enabled to be used (see zpool-features(5)).

mountpoint=path | none | legacy

    Controls the mount point used for this file system. See the "Mount Points" section for more information on how this property is used.

    When the mountpoint property is changed for a file system, the file system and any children that inherit the mount point are unmounted. If the new value is legacy, then they remain unmounted. Otherwise, they are automatically remounted in the new location if the property was previously legacy or none, or if they were mounted before the property was changed. In addition, any shared file systems are unshared and shared in the new location.

nbmand=off | on

    Controls whether the file system should be mounted with nbmand (Non Blocking mandatory locks). This is used for CIFS clients. Changes to this property only take effect when the file system is umounted and remounted. See mount(1M) on a Solaris system for more information on nbmand mounts.

    The values on and off are equivalent to the nbmand and nonbmand mount options.

    This property is not used on Linux.

primarycache=all | none | metadata

    Controls what is cached in the primary cache (ARC). If this property is set to all, then both user data and metadata is cached. If this property is set to none, then neither user data nor metadata is cached. If this property is set to metadata, then only metadata is cached. The default value is all.

quota=none | size

    Limits the amount of space a dataset and its descendents can consume. This property enforces a hard limit on the amount of space used. This includes all space consumed by descendents, including file systems and snapshots. Setting a quota on a descendent of a dataset that already has a quota does not override the ancestor's quota, but rather imposes an additional limit.

    Quotas cannot be set on volumes, as the volsize property acts as an implicit quota.

snapshot_limit=none | count

    Limits the number of snapshots that can be created on a dataset and its descendents. Setting a snapshot_limit on a descendent of a dataset that already has a snapshot_limit does not override the ancestor's snapshot_limit, but rather imposes an additional limit. The limit is not enforced if the user is allowed to change the limit. For example, this means that recursive snapshots taken from the global zone are counted against each delegated dataset within a zone. This feature must be enabled to be used (see zpool-features(5)).

userquota@user=none | size
userobjquota@user=none | count

    Limits the amount of space consumed by the specified user. Similar to the refquota property, the userquota space calculation does not include space that is used by descendent datasets, such as snapshots and clones. User space consumption is identified by the userspace@user property. See the zfs userspace subcommand for more information.

    Enforcement of user quotas may be delayed by several seconds. This delay means that a user might exceed their quota before the system notices that they are over quota and begins to refuse additional writes with the EDQUOT error message.

    Unprivileged users can only access their own groups' space usage. The root user, or a user who has been granted the userquota privilege with zfs allow, can get and set everyone's quota.

    This property is not available on volumes, on file systems before version 4, or on pools before version 15. The userquota@... properties are not displayed by zfs get all. The user's name must be appended after the @ symbol, using one of the following forms:

        o   POSIX name (for example, joe)

        o   POSIX numeric ID (for example, 789)

        o   SID name (for example, joe.smith@mydomain)

        o   SID numeric ID (for example, S-1-123-456-789)
Files created on Linux always have POSIX owners.
    The userobjquota is similar to userquota but it limits the number of objects a user can create. Please refer to userobjused for more information about how ZFS counts object usage.

groupquota@group=none | size
groupobjquota@group=none | count

    Limits the amount of space consumed by the specified group. Group space consumption is identified by the userquota@user property.

    Unprivileged users can access only their own groups' space usage. The root user, or a user who has been granted the groupquota privilege with zfs allow, can get and set all groups' quotas. The groupobjquota is similar to groupquota but it limits that the group can consume count number of objects at most. Please refer to userobjused for more information about how zfs counts object usage.

readonly=off | on

    Controls whether this dataset can be modified. The default value is off.

    This property can also be referred to by its shortened column name, rdonly.

    The values on and off are equivalent to the ro and rw mount options.

recordsize=size

    Specifies a suggested block size for files in the file system. This property is designed solely for use with database workloads that access files in fixed-size records. ZFS automatically tunes block sizes according to internal algorithms optimized for typical access patterns.

    For databases that create very large files but access them in small random chunks, these algorithms may be suboptimal. Specifying a recordsize greater than or equal to the record size of the database can result in significant performance gains. Use of this property for general purpose file systems is strongly discouraged, and may adversely affect performance.

    Any power of two from 512B to 1MiB is valid. The default is 128KiB. Values larger than 128KiB require the pool have the large_blocks feature enabled. See zpool-features(5) for details on ZFS feature flags and the large_blocks feature.

    Changing the file system's recordsize affects only files created afterward; existing files are unaffected.

    This property can also be referred to by its shortened column name, recsize.

redundant_metadata=all | most

    Controls what types of metadata are stored redundantly. ZFS stores an extra copy of metadata, so that if a single block is corrupted, the amount of user data lost is limited. This extra copy is in addition to any redundancy provided at the pool level (e.g. by mirroring or RAID-Z), and is in addition to an extra copy specified by the copies property (up to a total of 3 copies). For example if the pool is mirrored, copies=2, and redundant_metadata=most, then ZFS stores 6 copies of most metadata, and 4 copies of data and some metadata.

    When set to all, ZFS stores an extra copy of all metadata. If a single on-disk block is corrupt, at worst a single block of user data (which is recordsize bytes long) can be lost.

    When set to most, ZFS stores an extra copy of most types of metadata. This can improve performance of random writes, because less metadata must be written. In practice, at worst about 100 blocks (of recordsize bytes each) of user data can be lost if a single on-disk block is corrupt. The exact behavior of which metadata blocks are stored redundantly may change in future releases.

    The default value is all.

refquota=none | size

    Limits the amount of space a dataset can consume. This property enforces a hard limit on the amount of space used. This hard limit does not include space used by descendents, including file systems and snapshots.

refreservation=none | size

    The minimum amount of space guaranteed to a dataset, not including its descendents. When the amount of space used is below this value, the dataset is treated as if it were taking up the amount of space specified by refreservation. The refreservation reservation is accounted for in the parent datasets' space used, and counts against the parent datasets' quotas and reservations.

    If refreservation is set, a snapshot is only allowed if there is enough free pool space outside of this reservation to accommodate the current number of referenced bytes in the dataset (which are the bytes to be referenced by the snapshot). This is necessary to continue to provide the refreservationguarantee to the dataset.

    For volumes, see also volsize.

    This property can also be referred to by its shortened column name, refreserv.

relatime=off | on

    Controls the manner in which the access time is updated when atime=on is set. Turning this property on causes the access time to be updated relative to the modify or change time. Access time is only updated if the previous access time was earlier than the current modify or change time or if the existing access time hasn't been updated within the past 24 hours. The default value is off.

    The values on and off are equivalent to the relatime and norelatime mount options.

reservation=none | size

    The minimum amount of space guaranteed to a dataset and its descendents. When the amount of space used is below this value, the dataset is treated as if it were taking up the amount of space specified by its reservation. Reservations are accounted for in the parent datasets' space used, and count against the parent datasets' quotas and reservations.

    This property can also be referred to by its shortened column name, reserv.

secondarycache=all | none | metadata

    Controls what is cached in the secondary cache (L2ARC). If this property is set to all, then both user data and metadata is cached. If this property is set to none, then neither user data nor metadata is cached. If this property is set to metadata, then only metadata is cached. The default value is all.

setuid=on | off

    Controls whether the setuid bit is respected for the file system. The default value is on.

    The values on and off are equivalent to the suid and nosuid mount options.

sharesmb=off | on

    Controls whether the file system is shared by using Samba USERSHARES, and what options are to be used. Otherwise, the file system is automatically shared and unshared with the zfs share and zfs unshare commands. If the property is set to on, the net(8) command is invoked to create a USERSHARE.

    Because SMB shares requires a resource name, a unique resource name is constructed from the dataset name. The constructed name is a copy of the dataset name except that the characters in the dataset name, which would be invalid in the resource name, are replaced with underscore (_) characters. Linux does not currently support additional options which might be available on Solaris.

    If the sharesmb property is set to off, the file systems are unshared.

    In Linux, the share is created with the ACL (Access Control List) "Everyone:F" ("F" stands for "full permissions", ie. read and write permissions) and no guest access (which means Samba must be able to authenticate a real user, system passwd/shadow, LDAP or smbpasswd based) by default. This means that any additional access control (disallow specific user specific access etc) must be done on the underlaying filesystem.

    Example to mount a SMB filesystem shared through ZFS (share/tmp): Note that a user and his/her password must be given!

    smbmount //127.0.0.1/share_tmp /mnt/tmp -o user=workgroup/turbo,password=obrut,uid=1000

    Minimal /etc/samba/smb.conf configuration

    * Samba will need to listen to 'localhost' (127.0.0.1) for the zfs utilities to communicate with Samba. This is the default behavior for most Linux distributions.

    * Samba must be able to authenticate a user. This can be done in a number of ways, depending on if using the system password file, LDAP or the Samba specific smbpasswd file. How to do this is outside the scope of this manual. Please refer to the smb.conf(5) manpage for more information.

    * See the USERSHARE section of the smb.conf(5) man page for all configuration options in case you need to modify any options to the share afterwards. Do note that any changes done with the 'net' command will be undone if the share is every unshared (such as at a reboot etc). In the future, ZoL will be able to set specific options directly using sharesmb=<option>.

sharenfs=off | on | opts

    Controls whether the file system is shared via NFS, and what options are used. A file system with a sharenfs property of off is managed with the exportfs(8) command and entries in /etc/exports file. Otherwise, the file system is automatically shared and unshared with the zfs share and zfs unshare commands. If the property is set to on, the dataset is shared using the exportfs(8) command in the following manner (see exportfs(8) for the meaning of the different options):

    /usr/sbin/exportfs -i -o sec=sys,rw,no_subtree_check,no_root_squash,mountpoint *:<mountpoint of dataset>

    Otherwise, the exportfs(8) command is invoked with options equivalent to the contents of this property.

    When the sharenfs property is changed for a dataset, the dataset and any children inheriting the property are re-shared with the new options, only if the property was previously off, or if they were shared before the property was changed. If the new property is off, the file systems are unshared.

logbias=latency | throughput

    Provide a hint to ZFS about handling of synchronous requests in this dataset. If logbias is set to latency (the default), ZFS will use pool log devices (if configured) to handle the requests at low latency. If logbias is set to throughput, ZFS will not use configured pool log devices. ZFS will instead optimize synchronous operations for global pool throughput and efficient use of resources.

snapdev=hidden | visible

    Controls whether the snapshots devices of zvol's are hidden or visible. The default value is hidden.

    In this context, hidden does not refer to the concept of hiding files or directories by starting their name with a "." character. Even with visible, the directory is still named .zfs. Instead, hidden means that the directory is not returned by readdir(3), so it doesn't show up in directory listings done by any program, including ls -a. It is still possible to chdir(2) into the directory, so cd .zfs works even with hidden. This unusual behavior is to protect against unwanted effects from applications recursing into the special .zfs directory.

snapdir=hidden | visible

    Controls whether the .zfs directory is hidden or visible in the root of the file system as discussed in the "Snapshots" section. The default value is hidden.

sync=standard | always | disabled

    Controls the behavior of synchronous requests (e.g. fsync, O_DSYNC). standard is the POSIX specified behavior of ensuring all synchronous requests are written to stable storage and all devices are flushed to ensure data is not cached by device controllers (this is the default). always causes every file system transaction to be written and flushed before its system call returns. This has a large performance penalty. disabled disables synchronous requests. File system transactions are only committed to stable storage periodically. This option will give the highest performance. However, it is very dangerous as ZFS would be ignoring the synchronous transaction demands of applications such as databases or NFS. Administrators should only use this option when the risks are understood.

version=5 | 4 | 3 | 2 | 1 | current

    The on-disk version of this file system, which is independent of the pool version. This property can only be set to later supported versions. The value current automatically selects the latest supported version. See the zfs upgrade command.

volsize=size

    For volumes, specifies the logical size of the volume. By default, creating a volume establishes a refreservation equal to the volume size plus the metadata required for a fully-written volume. (For pool version 8 or lower, a reservation is set instead.) Any changes to volsize are reflected in an equivalent change to the refreservation. The volsize can only be set to a multiple of volblocksize, and cannot be zero.

    Without the reservation, the volume could run out of space, resulting in undefined behavior or data corruption, depending on how the volume is used. These effects can also occur when the volume size is changed while it is in use (particularly when shrinking the size). Extreme care should be used when adjusting the volume size.

    A "sparse volume" (also known as "thin provisioning") can be created by specifying the -s option to the zfs create -V command, or by removing (or changing) the refreservation after the volume has been created. A "sparse volume" is a volume where the refreservation is unset or less then the volume size. Consequently, writes to a sparse volume can fail with ENOSPC when the pool is low on space. For a sparse volume, changes to volsize are not reflected in the reservation.

vscan=off | on

    Controls whether regular files should be scanned for viruses when a file is opened and closed. In addition to enabling this property, the virus scan service must also be enabled for virus scanning to occur. The default value is off.

    This property is not used on Linux.

xattr=on | off | sa

    Controls whether extended attributes are enabled for this file system. Two styles of extended attributes are supported either directory based or system attribute based.

    The default value of on enables directory based extended attributes. This style of xattr imposes no practical limit on either the size or number of xattrs which may be set on a file. Although under Linux the getxattr(2) and setxattr(2) system calls limit the maximum xattr size to 64K. This is the most compatible style of xattr and it is supported by the majority of ZFS implementations.

    System attribute based xattrs may be enabled by setting the value to sa. The key advantage of this type of xattr is improved performance. Storing xattrs as system attributes significantly decreases the amount of disk IO required. Up to 64K of xattr data may be stored per file in the space reserved for system attributes. If there is not enough space available for an xattr then it will be automatically written as a directory based xattr. System attribute based xattrs are not accessible on platforms which do not support the xattr=sa feature.

    The use of system attribute based xattrs is strongly encouraged for users of SELinux or Posix ACLs. Both of these features heavily rely of xattrs and benefit significantly from the reduced xattr access time.

    The values on and off are equivalent to the xattr and noxattr mount options.

zoned=off | on

    Controls whether the dataset is managed from a non-global zone. Zones are a Solaris feature and are not relevant on Linux. The default value is off.

The following three properties cannot be changed after the file system is created, and therefore, should be set when the file system is created. If the properties are not set with the zfs create or zpool create commands, these properties are inherited from the parent dataset. If the parent dataset lacks these properties due to having been created prior to these features being supported, the new file system will have the default values for these properties.

casesensitivity=sensitive | insensitive | mixed

    Indicates whether the file name matching algorithm used by the file system should be case-sensitive, case-insensitive, or allow a combination of both styles of matching. The default value for the casesensitivity property is sensitive. Traditionally, UNIX and POSIX file systems have case-sensitive file names.

    The mixed value for the casesensitivity property indicates that the file system can support requests for both case-sensitive and case-insensitive matching behavior. Currently, case-insensitive matching behavior on a file system that supports mixed behavior is limited to the Solaris CIFS server product.

normalization = none | formC | formD | formKC | formKD

    Indicates whether the file system should perform a Unicode normalization of file names whenever two file names are compared, and which normalization algorithm should be used.

    If this property is set to a value other than none (the default), and the utf8only property was left unspecified, the utf8only property is automatically set to on. See the cautionary note in the utf8only section before modifying normalization.

    File names are always stored unmodified; names are normalized as part of any comparison process. Thus, formC and formD are equivalent, as are formKC and formKD. Given that, only formD and formKD make sense, as they are slightly faster because they avoid the additional canonical composition step.

    The practical impact of this property is: none (like traditional filesystems) allows a directory to contain two files that appear (to humans) to have the same name. The other options solve this problem, for different definitions of "the same". If you need to solve this problem and are not sure what to choose,formD.

    This property cannot be changed after the file system is created.

utf8only=off | on

    Indicates whether the file system should reject file names that include characters that are not present in the UTF-8 character set. If this property is explicitly set to off, the normalization property must either not be explicitly set or be set to none. The default value for the utf8only property is off.

    Note that forcing the use of UTF-8 filenames may cause pain for users. For example, extracting files from an archive will fail if the filenames within the archive are encoded in another character set.

    If you are thinking of setting this (to on), you probably want to set normalization=formD which will set this property to on implicitly.

    This property cannot be changed after the file system is created.

The casesensitivity, normalization, and utf8only properties are also permissions that can be assigned to non-privileged users by using the ZFS delegated administration feature.

context=none | SELinux_User:SElinux_Role:Selinux_Type:Sensitivity_Level

    This flag sets the SELinux context for all files in the filesystem under the mountpoint for that filesystem. See selinux(8) for more information.

fscontext=none | SELinux_User:SElinux_Role:Selinux_Type:Sensitivity_Level

    This flag sets the SELinux context for the filesystem being mounted. See selinux(8) for more information.

defcontext=none | SELinux_User:SElinux_Role:Selinux_Type:Sensitivity_Level

    This flag sets the SELinux context for unlabeled files. See selinux(8) for more information.

rootcontext=none | SELinux_User:SElinux_Role:Selinux_Type:Sensitivity_Level

    This flag sets the SELinux context for the root inode of the filesystem. See selinux(8) for more information.

overlay=off | on

    Allow mounting on a busy directory or a directory which already contains files/directories. This is the default mount behavior for Linux filesystems. However, for consistency with ZFS on other platforms overlay mounts are disabled by default. Set overlay=on to enable overlay mounts.

  Temporary Mount Point Properties

When a file system is mounted, either through mount(8) for legacy mounts or the zfs mount command for normal file systems, its mount options are set according to its properties. The correlation between properties and mount options is as follows:

    PROPERTY                MOUNT OPTION
     atime                   atime/noatime
     canmount                auto/noauto
     devices                 devices/nodevices
     exec                    exec/noexec
     readonly                ro/rw
     relatime                relatime/norelatime
     setuid                  suid/nosuid
     xattr                   xattr/noxattr
     nbmand                  nbmand/nonbmand (Solaris)

In addition, these options can be set on a per-mount basis using the -o option, without affecting the property that is stored on disk. The values specified on the command line override the values stored in the dataset. The -nosuid option is an alias for nodevices,nosetuid. These properties are reported as "temporary" by the zfs get command. If the properties are changed while the dataset is mounted, the new setting overrides any temporary settings.

  User Properties

In addition to the standard native properties, ZFS supports arbitrary user properties. User properties have no effect on ZFS behavior, but applications or administrators can use them to annotate datasets (file systems, volumes, and snapshots). Unlike native properties, user properties are editable on snapshots.

User property names must contain a colon (:) character to distinguish them from native properties. They may contain lowercase letters, numbers, and the following punctuation characters: colon (:), dash (-), period (.), and underscore (_). The expected convention is that the property name is divided into two portions such as module:property, but this namespace is not enforced by ZFS. User property names can be at most 256 characters, and cannot begin with a dash (-).

When making programmatic use of user properties, it is strongly suggested to use a reversed DNS domain name for the module component of property names to reduce the chance that two independently-developed packages use the same property name for different purposes. For example, property names beginning with com.sun. are reserved for definition by Oracle Corporation (which acquired Sun Microsystems).

The values of user properties are arbitrary strings, are always inherited, and are never validated. All of the commands that operate on properties (zfs list, zfs get, zfs set, and so forth) can be used to manipulate both native properties and user properties. Use the zfs inherit command to clear a user property. If the property is not defined in any parent dataset, it is removed entirely. Property values are limited to 1024 characters.

  ZFS Volumes as Swap

ZFS volumes may be used as Linux swap devices. After creating the volume with the zfs create command set up and enable the swap area using the mkswap(8) and swapon(8) commands. Do not swap to a file on a ZFS file system. A ZFS swap file configuration is not supported.

SUBCOMMANDS

All subcommands that modify state are logged persistently to the pool in their original form. The log can be viewed with zpool history.

zfs ?

    Displays a help message.

zfs create [-p] [-o property=value] ... filesystem

    Creates a new ZFS file system. The file system is automatically mounted according to the mountpoint and canmount properties.

    -p

        Creates all the non-existing parent datasets. Datasets created in this manner inherit their properties; any property specified on the command line using the -o option applies only to the final child file system. If the target filesystem already exists, the operation completes successfully and no properties are changed.

    -o property=value

        Sets the specified property as if the command zfs set property=value was invoked at the same time the dataset was created. Any editable ZFS property can also be set at creation time. Multiple -o options can be specified. An error results if the same property is specified in multiple -o options.

zfs create [-ps] [-b blocksize] [-o property=value] ... -V size volume

    Creates a volume of the given size. The volume is exported as a block device in /dev/zvol/path, where path is the name of the volume in the ZFS namespace. The size represents the logical size as exported by the device. By default, a refreservation is created.

    size is automatically rounded up to the nearest 128KiB to ensure that the volume has an integral number of blocks regardless of blocksize.

    -p

        Creates all the non-existing parent datasets as file systems. Datasets created in this manner inherit their properties; any property specified on the command line using the -o option applies only to the final child volume. If the target volume already exists, the operation completes successfully and no properties are changed.

    -s

        Creates a sparse volume by omitting the automatic creation of a refreservation. See volsize in the Native Properties section for more information about sparse volumes. If this option is specified in conjunction with -o refreservation, the refreservation will be honored; this allows for a partial reservation on a sparse volume.

    -o property=value

        Sets the specified property as if the zfs set property=value command was invoked at the same time the dataset was created. Any editable ZFS property can also be set at creation time. Multiple -o options can be specified. An error results if the same property is specified in multiple -o options.

        If -o volsize is provided, the resulting behavior is undefined; it conflicts with the -V option, which is required in this mode.

    -b blocksize

        Equivalent to -o volblocksize=blocksize. If this option is specified in conjunction with -o volblocksize, the resulting behavior is undefined.

zfs destroy [-fnpRrv] filesystem|volume

    Destroys the given dataset. By default, the command unshares any file systems that are currently shared, unmounts any file systems that are currently mounted, and refuses to destroy a dataset that has active dependents (children or clones).

    -r

        Recursively destroy all children.

    -R

        Recursively destroy all dependents, including cloned file systems outside the target hierarchy.

    -f

        Force an unmount of any file systems using the zfs unmount -f command. This option has no effect on non-file systems or unmounted file systems.

    -n

        Do a dry-run ("No-op") deletion. No data will be deleted. This is useful in conjunction with the -v or -p flags to determine what data would be deleted.

    -p

        Print machine-parsable verbose information about the deleted data.

    -v

        Print verbose information about the deleted data.

    Extreme care should be taken when applying either the -r or the -R options, as they can destroy large portions of a pool.

zfs destroy [-dnpRrv] filesystem|volume@snap[%snap][,...]

    The specified snapshots are destroyed immediately if they have no clones and the user-initiated reference count is zero (i.e. there are no holds set with zfs hold). If these conditions are not met, this command returns an error, unless -d is supplied.

    An inclusive range of snapshots may be specified by separating the first and last snapshots with a percent sign. The first and/or last snapshots may be left blank, in which case the filesystem's oldest or newest snapshot will be implied.

    Multiple snapshots (or ranges of snapshots) of the same filesystem or volume may be specified in a comma-separated list of snapshots. Only the snapshot's short name (the part after the @) should be specified when using a range or comma-separated list to identify multiple snapshots.

    -d

        If a snapshot does not qualify for immediate destruction, rather than returning an error, it is marked for deferred destruction. In this state, it exists as a usable, visible snapshot until both of the preconditions listed above are met, at which point it is destroyed.

    -r

        Destroy (or mark for deferred destruction) all snapshots with this name in descendent file systems.

    -R

        Recursively destroy all clones of these snapshots, including the clones, snapshots, and children. If this flag is specified, the -d flag will have no effect.

    -n

        Do a dry-run ("No-op") deletion. No data will be deleted. This is useful in conjunction with the -v or -p flags to determine what data would be deleted.

    -p

        Print machine-parsable verbose information about the deleted data.

    -v

        Print verbose information about the deleted data.

    Extreme care should be taken when applying either the -r or the -R options, as they can destroy large portions of a pool and cause unexpected behavior for mounted file systems in use.

zfs destroy filesystem|volume#bookmark

    The given bookmark is destroyed.

zfs snapshot [-r] [-o property=value] ... filesystem@snapname|volume@snapname ...

    Creates snapshots with the given names. All previous modifications by successful system calls to the file system are part of the snapshots. Snapshots are taken atomically, so that all snapshots correspond to the same moment in time. See the "Snapshots" section for details.

    -r

        Recursively create snapshots of all descendent datasets.

    -o property=value

        Sets the specified property; see zfs set for details.

zfs rollback [-rRf] snapshot

    Roll back the given dataset to a previous snapshot. When a dataset is rolled back, all data that has changed since the snapshot is discarded, and the dataset reverts to the state at the time of the snapshot. By default, the command refuses to roll back to a snapshot other than the most recent one. In order to do so, all intermediate snapshots and bookmarks must be destroyed by specifying the -r option.

    The -rR options do not recursively destroy the child snapshots of a recursive snapshot. Only direct snapshots of the specified filesystem are destroyed by either of these options. To completely roll back a recursive snapshot, you must rollback the individual child snapshots.

    -r

        Destroy any snapshots and bookmarks more recent than the one specified.

    -R

        Recursively destroy any more recent snapshots and bookmarks, as well as any clones of those snapshots.

    -f

        Used with the -R option to force an unmount (see zfs unmount -f) of any clone file systems that are to be destroyed.

zfs clone [-p] [-o property=value] ... snapshot filesystem|volume

    Creates a clone of the given snapshot. See the "Clones" section for details. The target dataset can be located anywhere in the ZFS hierarchy, and is created as the same type as the original.

    -p

        Creates all the non-existing parent datasets; see zfs create for details.

    -o property=value

        Sets the specified property; see zfs set for details.

zfs promote clone-filesystem

    Promotes a clone file system to no longer be dependent on its "origin" snapshot. This makes it possible to destroy the file system that the clone was created from. The clone parent-child dependency relationship is reversed, so that the origin file system becomes a clone of the specified file system.

    The snapshot that was cloned, and any snapshots previous to this snapshot, are now owned by the promoted clone. The space they use moves from the origin file system to the promoted clone, so enough space must be available to accommodate these snapshots. No new space is consumed by this operation, but the space accounting is adjusted. The promoted clone must not have any conflicting snapshot names of its own. The zfs rename command can be used to rename any conflicting snapshots.

zfs rename [-f] filesystem|volume|snapshot
zfs rename [-fp] filesystem|volume filesystem|volume

    Renames the given dataset. The new target can be located anywhere in the ZFS hierarchy, with the exception of snapshots. Snapshots can only be renamed within the parent file system or volume. When renaming a snapshot, the parent file system of the snapshot does not need to be specified as part of the second argument. Renamed file systems can inherit new mount points, in which case they are unmounted and remounted at the new mount point.

    -p

        Creates all the nonexistent parent datasets; see zfs create for details.

    -f

        Force unmount any filesystems that need to be unmounted in the process.

zfs rename -r snapshot snapshot

    Recursively rename the snapshots of all descendent datasets. Snapshots are the only dataset that can be renamed recursively.

zfs list [-r|-d depth] [-Hp] [-o property[,...]] [ -t type[,...]] [ -s property ] ... [ -S property ] ... [filesystem|volume|snapshot|mountpoint] ...

    Lists the property information for the given datasets in tabular form. If a mount point is specified, it can be an absolute pathname or a relative pathname starting with "./" (e.g. zfs list ./). By default, all file systems and volumes are displayed. Snapshots are displayed if the pool's listsnapshots property is on (the default is off). When listing hundreds or thousands of snapshots performance can be improved by restricting the output to only the name. In that case, it is recommended to use -o name -s name. The following fields are displayed by default: name, used, available, referenced, mountpoint

    -H

        Used for scripting mode. Do not print headers and separate fields by a single tab instead of arbitrary white space.

    -p

        Display numbers in parsable (exact) values.

    -r

        Recursively display any children of the dataset on the command line.

    -d depth

        Recursively display any children of the dataset, limiting the recursion to depth. A depth of 1 will display only the dataset and its direct children.

    -o property

        A comma-separated list of properties to display. The property must be:

            o   One of the properties described in the "Native Properties" section

            o   A user property

            o   The value name to display the dataset name

            o   The value space to display space usage properties on file systems and volumes. This is a shortcut for specifying -o name,avail,used,usedsnap,usedds,usedrefreserv,usedchild -t filesystem,volume syntax.

    -s property

        A property for sorting the output by column in ascending order based on the value of the property. The property must be one of the properties described in the "Properties" section, or the special value name to sort by the dataset name. Multiple properties can be specified at one time using multiple -s property options. Multiple -s options are evaluated from left to right in decreasing order of importance.

        The following is a list of sorting criteria:

            o   Numeric types sort in numeric order.

            o   String types sort in alphabetical order.

            o   Types inappropriate for a row sort that row to the literal bottom, regardless of the specified ordering.

            o   If no sorting options are specified the existing behavior of zfs list is preserved.

    -S property

        Same as the -s option, but sorts by property in descending order.

    -t type

        A comma-separated list of types to display, where type is one of filesystem, snapshot, snap, volume, bookmark, or all. For example, specifying -t snapshot displays only snapshots.

zfs set property=value[ property=value]... filesystem|volume|snapshot ...

    Sets the property or list of properties to the given value(s) for each dataset. Only some properties can be edited. See the "Properties" section for more information on which properties can be set and acceptable values. User properties can be set on snapshots. For more information, see the "User Properties" section.

zfs get [-r|-d depth] [-Hp] [-o field[,...] [-t type[,...]] [-s source[,...] "all" | property[,...] filesystem|volume|snapshot ...

    Displays properties for the given datasets. If no datasets are specified, then the command displays properties for all datasets on the system. For each property, the following columns are displayed:

        name      Dataset name
         property  Property name
         value     Property value
         source    Property source. Can either be local, default,
                   temporary, inherited, received, or none (-).

    All columns are displayed by default, though this can be controlled by using the -o option. This command takes a comma-separated list of properties as described in the "Native Properties" and "User Properties" sections.

    The special value all can be used to display all properties that apply to the given dataset's type (filesystem, volume snapshot, or bookmark).

    -r

        Recursively display properties for any children.

    -d depth

        Recursively display any children of the dataset, limiting the recursion to depth. A depth of 1 will display only the dataset and its direct children.

    -H

        Display output in a form more easily parsed by scripts. Any headers are omitted, and fields are explicitly separated by a single tab instead of an arbitrary amount of space.

    -o field

        A comma-separated list of columns to display. name,property,value,source is the default value.

    -s source

        A comma-separated list of sources to display. Those properties coming from a source other than those in this list are ignored. Each source must be one of the following: local,default,inherited,received,temporary,none. The default value is all sources.

    -p

        Display numbers in parsable (exact) values.

zfs inherit [-rS] property filesystem|volume|snapshot ...

    Clears the specified property, causing it to be inherited from an ancestor, restored to default if no ancestor has the property set, or with the -S option reverted to the received value if one exists. See the "Properties" section for a listing of default values, and details on which properties can be inherited.

    -r

        Recursively inherit the given property for all children.

    -S

        Revert the property to the received value if one exists; otherwise operate as if the -S option was not specified.

zfs upgrade

    Displays a list of file systems that are not the most recent version.

zfs upgrade -v

    Displays a list of file system versions.

zfs upgrade [-r] [-V version] [-a | filesystem]

    Upgrades file systems to a new on-disk version. Once this is done, the file systems will no longer be accessible on systems running older versions of the software. zfs send streams generated from new snapshots of these file systems cannot be accessed on systems running older versions of the software.

    In general, the file system version is independent of the pool version. See zpool(8) for information on the zpool upgrade command.

    In some cases, the file system version and the pool version are interrelated and the pool version must be upgraded before the file system version can be upgraded.

    -a

        Upgrades all file systems on all imported pools.

    filesystem

        Upgrades the specified file system.

    -r

        Upgrades the specified file system and all descendent file systems

    -V version

        Upgrades to the specified version. If the -V flag is not specified, this command upgrades to the most recent version. This option can only be used to increase the version number, and only up to the most recent version supported by this software.

zfs userspace [-Hinp] [-o field[,...]] [-s field] ... [-S field] ... [-t type[,...]] filesystem|snapshot

    Displays space consumed by, and quotas on, each user in the specified filesystem or snapshot. This corresponds to the userused@user, userobjused@user, userquota@user, and userobjquota@user properties.

    -n

        Print numeric ID instead of user/group name.

    -H

        Display output in a form more easily parsed by scripts. Any headers are omitted, and fields are explicitly separated by a single tab instead of an arbitrary amount of space.

    -p

        Use exact (parsable) numeric output.

    -o field[,...]

        Display only the specified fields from the following set: type, name, used, quota. The default is to display all fields.

    -s field

        Sort output by this field. The s and S flags may be specified multiple times to sort first by one field, then by another. The default is -s type -s name.

    -S field

        Sort by this field in reverse order. See -s.

    -t type[,...]

        Print only the specified types from the following set: all, posixuser, smbuser, posixgroup, smbgroup. The default is -t posixuser,smbuser. The default can be changed to include group types.

    -i

        Translate SID to POSIX ID. The POSIX ID may be ephemeral if no mapping exists. Normal POSIX interfaces (for example, stat(2), ls(1) -l) perform this translation, so the -i option allows the output from zfs userspace to be compared directly with those utilities. However, -i may lead to confusion if some files were created by an SMB user before a SMB-to-POSIX name mapping was established. In such a case, some files will be owned by the SMB entity and some by the POSIX entity. However, the -i option will report that the POSIX entity has the total usage and quota for both.

        This option is not useful on Linux.

zfs groupspace [-Hinp] [-o field[,...]] [-s field] ... [-S field] ... [-t type[,...]] filesystem|snapshot

    Displays space consumed by, and quotas on, each group in the specified filesystem or snapshot. This subcommand is identical to zfs userspace, except that the default types to display are -t posixgroup,smbgroup.

zfs mount

    Displays all ZFS file systems currently mounted.

zfs mount [-vO] [-o options] -a | filesystem

    Mounts ZFS file systems. This is invoked automatically as part of the boot process.

    -o options

        An optional, comma-separated list of mount options to use temporarily for the duration of the mount. See the "Temporary Mount Point Properties" section for details.

    -O

        Allow mounting the filesystem even if the target directory is not empty.

        On Solaris, the behavior of zfs mount matches mount and zfs mount -O matches mount -O. See mount(1M).

        On Linux, this is the default for mount(8). In other words, zfs mount -O matches mount and there is no mount equivalent to a plain zfs mount.

    -v

        Report mount progress. This is intended for use with zfs mount -a on a system with a significant number of filesystems.

    -a

        Mount all available ZFS file systems. Invoked automatically as part of the boot process.

    filesystem

        Mount the specified filesystem.

zfs unmount [-f] -a | filesystem|mountpoint

    Unmounts currently mounted ZFS file systems. Invoked automatically as part of the shutdown process.

    -f

        Forcefully unmount the file system, even if it is currently in use.

    -a

        Unmount all available ZFS file systems. Invoked automatically as part of the shutdown process.

    filesystem|mountpoint

        Unmount the specified filesystem. The command can also be given a path to a ZFS file system mount point on the system.

zfs share -a | filesystem

    Shares available ZFS file systems.

    -a

        Share all available ZFS file systems. Invoked automatically as part of the boot process.

    filesystem

        Share the specified filesystem according to the sharenfs and sharesmb properties. File systems are shared when the sharenfs or sharesmb property is set.

zfs unshare -a | filesystem|mountpoint

    Unshares currently shared ZFS file systems. This is invoked automatically as part of the shutdown process.

    -a

        Unshare all available ZFS file systems. Invoked automatically as part of the boot process.

    filesystem|mountpoint

        Unshare the specified filesystem. The command can also be given a path to a ZFS file system shared on the system.

zfs bookmark snapshot bookmark

    Creates a bookmark of the given snapshot. Bookmarks mark the point in time when the snapshot was created, and can be used as the incremental source for a zfs send command.

    This feature must be enabled to be used. See zpool-features(5) for details on ZFS feature flags and the bookmarks feature.

zfs send [-DnPpRveLc] [-[iI] snapshot] snapshot

    Creates a stream representation of the (second, if -i is specified) snapshot, which is written to standard output. The output can be redirected to a file or to a pipe (for example, using ssh(1) to send it to a different system with zfs receive). By default, a full stream is generated; specifying -i or -I changes this behavior.

    -i snapshot

        Generate an incremental stream from the first snapshot (the incremental source) to the second snapshot (the incremental target). The incremental source can be specified as the last component of the snapshot name (the @ character and following) and it is assumed to be from the same file system as the incremental target.

        If the destination is a clone, the source may be the origin snapshot, which must be fully specified (for example, pool/fs@origin, not just @origin).

    -I snapshot

        Generate a stream package that sends all intermediary snapshots from the first snapshot to the second snapshot. For example, -I @a fs@d is similar to -i @a fs@b; -i @b fs@c; -i @c fs@d. The incremental source may be specified as with the -i option.

    -R

        Generate a replication stream package, which will replicate the specified filesystem, and all descendent file systems, up to the named snapshot. When received, all properties, snapshots, descendent file systems, and clones are preserved.

        If the -i or -I flags are used in conjunction with the -R flag, an incremental replication stream is generated. The current values of properties, and current snapshot and file system names are set when the stream is received. If the -F flag is specified when this stream is received, snapshots and file systems that do not exist on the sending side are destroyed.

    -D

        Generate a deduplicated stream. Blocks which would have been sent multiple times in the send stream will only be sent once. The receiving system must also support this feature to receive a deduplicated stream. This flag can be used regardless of the dataset's dedup property, but performance will be much better if the filesystem uses a dedup-capable checksum (eg. sha256).

    -L

        Generate a stream which may contain blocks larger than 128KiB. This flag has no effect if the large_blocks pool feature is disabled, or if the recordsize property of this filesystem has never been set above 128KiB. The receiving system must have the large_blocks pool feature enabled as well. See zpool-features(5) for details on ZFS feature flags and the large_blocks feature.

    -e

        Generate a more compact stream by using WRITE_EMBEDDED records for blocks which are stored more compactly on disk by the embedded_data pool feature. This flag has no effect if the embedded_data feature is disabled. The receiving system must have the embedded_data feature enabled. If the lz4_compress feature is active on the sending system, then the receiving system must have that feature enabled as well. See zpool-features(5) for details on ZFS feature flags and the embedded_data feature.

    -c, --compressed

        Generate a more compact stream by using compressed WRITE records for blocks which are compressed on disk and in memory (see the compression property for details). If the lz4_compress feature is active on the sending system, then the receiving system must have that feature enabled as well. If the large_blocks feature is enabled on the sending system but the -L option is not supplied in conjunction with -c, then the data will be decompressed before sending so it can be split into smaller block sizes.

    -p

        Include the dataset's properties in the stream. This flag is implicit when -R is specified. The receiving system must also support this feature.

    -n

        Do a dry-run ("No-op") send. Do not generate any actual send data. This is useful in conjunction with the -v or -P flags to determine what data will be sent. In this case, the verbose output will be written to standard output (contrast with a non-dry-run, where the stream is written to standard output and the verbose output goes to standard error).

    -P

        Print machine-parsable verbose information about the stream package generated.

    -v

        Print verbose information about the stream package generated. This information includes a per-second report of how much data has been sent.
    The format of the stream is committed. You will be able to receive your streams on future versions of ZFS.

zfs send [-Lec] [-i snapshot|bookmark] filesystem|volume|snapshot

    Generate a send stream, which may be of a filesystem, and may be incremental from a bookmark. If the destination is a filesystem or volume, the pool must be read-only, or the filesystem must not be mounted. When the stream generated from a filesystem or volume is received, the default snapshot name will be "--head--".

    -L

        Generate a stream which may contain blocks larger than 128KiB. This flag has no effect if the large_blocks pool feature is disabled, or if the recordsize property of this filesystem has never been set above 128KiB. The receiving system must have the large_blocks pool feature enabled as well. See zpool-features(5) for details on ZFS feature flags and the large_blocks feature.

    -e

        Generate a more compact stream by using WRITE_EMBEDDED records for blocks which are stored more compactly on disk by the embedded_data pool feature. This flag has no effect if the embedded_data feature is disabled. The receiving system must have the embedded_data feature enabled. If the lz4_compress feature is active on the sending system, then the receiving system must have that feature enabled as well. See zpool-features(5) for details on ZFS feature flags and the embedded_data feature.

    -c, --compressed

        Generate a more compact stream by using compressed WRITE records for blocks which are compressed on disk and in memory (see the compression property for details). If the lz4_compress feature is active on the sending system, then the receiving system must have that feature enabled as well. If the large_blocks feature is enabled on the sending system but the -L option is not supplied in conjunction with -c, then the data will be decompressed before sending so it can be split into smaller block sizes.

    -i snapshot|bookmark

        Generate an incremental send stream. The incremental source must be an earlier snapshot in the destination's history. It will commonly be an earlier snapshot in the destination's filesystem, in which case it can be specified as the last component of the name (the # or @ character and following).

        If the incremental target is a clone, the incremental source can be the origin snapshot, or an earlier snapshot in the origin's filesystem, or the origin's origin, etc.

zfs send [-Penv] -t receive_resume_token

    Creates a send stream which resumes an interrupted receive. The receive_resume_token is the value of this property on the filesystem or volume that was being received into. See the documentation for zfs receive -s for more details.

zfs receive [-Fnsuv] [-o origin=snapshot] filesystem|volume|snapshot
zfs receive [-Fnsuv] [-d|-e] [-o origin=snapshot] filesystem

    Creates a snapshot whose contents are as specified in the stream provided on standard input. If a full stream is received, then a new file system is created as well. Streams are created using the zfs send subcommand, which by default creates a full stream. zfs recv can be used as an alias for zfs receive.

    If an incremental stream is received, then the destination file system must already exist, and its most recent snapshot must match the incremental stream's source. For zvols, the destination device link is destroyed and recreated, which means the zvol cannot be accessed during the receive operation.

    When a snapshot replication package stream that is generated by using the zfs send -R command is received, any snapshots that do not exist on the sending location are destroyed by using the zfs destroy -d command.

    The name of the snapshot (and file system, if a full stream is received) that this subcommand creates depends on the argument type and the use of the -d or -e options.

    If the argument is a snapshot name, the specified snapshot is created. If the argument is a file system or volume name, a snapshot with the same name as the sent snapshot is created within the specified filesystem or volume. If neither of the -d or -e options are specified, the provided target snapshot name is used exactly as provided.

    The -d and -e options cause the file system name of the target snapshot to be determined by appending a portion of the sent snapshot's name to the specified target filesystem. If the -d option is specified, all but the first element of the sent snapshot's file system path (usually the pool name) is used and any required intermediate file systems within the specified one are created. If the -e option is specified, then only the last element of the sent snapshot's file system name (i.e. the name of the source file system itself) is used as the target file system name.

    -F

        Force a rollback of the file system to the most recent snapshot before performing the receive operation. If receiving an incremental replication stream (for example, one generated by zfs send -R -[iI]), destroy snapshots and file systems that do not exist on the sending side.

    -n

        Do not actually receive the stream. This can be useful in conjunction with the -v option to verify the name the receive operation would use.

    -s

        If the receive is interrupted, save the partially received state, rather than deleting it. Interruption may be due to premature termination of the stream (e.g. due to network failure or failure of the remote system if the stream is being read over a network connection), a checksum error in the stream, termination of the zfs receive process, or unclean shutdown of the system.

        The receive can be resumed with a stream generated by zfs send -t token, where the token is the value of the receive_resume_token property of the filesystem or volume which is received into.

        To use this flag, the storage pool must have the extensible_dataset feature enabled. See zpool-features(5) for details on ZFS feature flags.

    -u

        Do not mount the file system that is associated with the received stream.

    -v

        Print verbose information about the stream and the time required to perform the receive operation.

    -d

        Discard the first element of the sent snapshot's file system name, using the remaining elements to determine the name of the target file system for the new snapshot as described in the paragraph above.

    -e

        Discard all but the last element of the sent snapshot's file system name, using that element to determine the name of the target file system for the new snapshot as described in the paragraph above.

    -o origin=snapshot

        Forces the stream to be received as a clone of the given snapshot. If the stream is a full send stream, this will create the filesystem described by the stream as a clone of the specified snapshot. Which snapshot was specified will not affect the success or failure of the receive, as long as the snapshot does exist. If the stream is an incremental send stream, all the normal verification will be performed.

zfs receive [-A] filesystem|volume

    Abort an interrupted zfs receive -s, deleting its saved partially received state.

zfs allow filesystem | volume

    Displays permissions that have been delegated on the specified filesystem or volume. See the other forms of zfs allow for more information.

    Delegations are supported under Linux with the exception of mount, unmount, mountpoint, canmount, rename, and share. These permissions cannot be delegated because the Linux mount(8) command restricts modifications of the global namespace to the root user.

zfs allow [-ldug] "everyone"|user|group[,...] perm|@setname[,...] filesystem| volume
zfs allow [-ld] -e perm|@setname[,...] filesystem | volume

    Delegates ZFS administration permission for the file systems to non-privileged users.

    [-ug] "everyone"|user|group[,...]

        Specifies to whom the permissions are delegated. Multiple entities can be specified as a comma-separated list. If neither of the -ug options are specified, then the argument is interpreted preferentially as the keyword "everyone", then as a user name, and lastly as a group name. To specify a user or group named "everyone", use the -u or -g options. To specify a group with the same name as a user, use the -g options.

    [-e] perm|@setname[,...]

        Specifies that the permissions be delegated to "everyone." Multiple permissions may be specified as a comma-separated list. Permission names are the same as ZFS subcommand and property names. See the property list below. Property set names, which begin with an at sign (@) , may be specified. See the -s form below for details.

    [-ld] filesystem|volume

        Specifies where the permissions are delegated. If neither of the -ld options are specified, or both are, then the permissions are allowed for the file system or volume, and all of its descendents. If only the -l option is used, then is allowed "locally" only for the specified file system. If only the -d option is used, then is allowed only for the descendent file systems.

Permissions are generally the ability to use a zfs subcommand or change a property. The following permissions are available:

NAME             TYPE           NOTES
allow            subcommand     Must also have the permission that is being
                                allowed
clone            subcommand     Must also have the 'create' ability and 'mount'
                                ability in the origin file system
create           subcommand     Must also have the 'mount' ability
destroy          subcommand     Must also have the 'mount' ability
diff             subcommand     Allows lookup of paths within a dataset
                                given an object number, and the ability to
                                create snapshots necessary to 'zfs diff'.
mount            subcommand     Allows mount/umount of ZFS datasets
promote          subcommand     Must also have the 'mount'
                                and 'promote' ability in the origin file system
receive          subcommand     Must also have the 'mount' and 'create' ability
rename           subcommand     Must also have the 'mount' and 'create'
                                ability in the new parent
rollback         subcommand     Must also have the 'mount' ability
send             subcommand
share            subcommand     Allows sharing file systems over NFS or SMB
                                protocols
snapshot         subcommand     Must also have the 'mount' ability
groupobjquota    other          Allows accessing any groupobjquota@... property
groupquota       other          Allows accessing any groupquota@... property
groupobjused     other          Allows reading any groupobjused@... property
groupused        other          Allows reading any groupused@... property
userprop         other          Allows changing any user property
userobjquota     other          Allows accessing any userobjquota@... property
userquota        other          Allows accessing any userquota@... property
userobjused      other          Allows reading any userobjused@... property
userused         other          Allows reading any userused@... property
acltype          property
aclinherit       property
atime            property
canmount         property
casesensitivity  property
checksum         property
compression      property
copies           property
dedup            property
devices          property
exec             property
filesystem_limit property
logbias          property
mlslabel         property
mountpoint       property
nbmand           property
normalization    property
primarycache     property
quota            property
readonly         property
recordsize       property
refquota         property
refreservation   property
reservation      property
secondarycache   property
setuid           property
sharenfs         property
sharesmb         property
snapdir          property
snapshot_limit   property
utf8only         property
version          property
volblocksize     property
volsize          property
vscan            property
xattr            property
zoned            property

zfs allow -c perm|@setname[,...] filesystem|volume

    Sets "create time" permissions. These permissions are granted (locally) to the creator of any newly-created descendent file system.

zfs allow -s @setname perm|@setname[,...] filesystem|volume

    Defines or adds permissions to a permission set. The set can be used by other zfs allow commands for the specified file system and its descendents. Sets are evaluated dynamically, so changes to a set are immediately reflected. Permission sets follow the same naming restrictions as ZFS file systems, but the name must begin with an "at sign" (@), and can be no more than 64 characters long.

zfs unallow [-rldug] "everyone"|user|group[,...] [perm|@setname[, ...]] filesystem|volume
zfs unallow [-rld] -e [perm|@setname [,...]] filesystem|volume
zfs unallow [-r] -c [perm|@setname[,...]] filesystem|volume

    Removes permissions that were granted with the zfs allow command. No permissions are explicitly denied, so other permissions granted are still in effect. For example, if the permission is granted by an ancestor. If no permissions are specified, then all permissions for the specified user, group, or everyone are removed. Specifying "everyone" (or using the -e option) only removes the permissions that were granted to "everyone", not all permissions for every user and group. See the zfs allow command for a description of the -ldugec options.

    -r

        Recursively remove the permissions from this file system and all descendents.

zfs unallow [-r] -s @setname [perm|@setname[,...]] filesystem|volume

    Removes permissions from a permission set. If no permissions are specified, then all permissions are removed, thus removing the set entirely.

zfs hold [-r] tag snapshot...

    Adds a single reference, named with the tag argument, to the specified snapshot or snapshots. Each snapshot has its own tag namespace, and tags must be unique within that space.

    If a hold exists on a snapshot, attempts to destroy that snapshot by using the zfs destroy command return EBUSY.

    -r

        Specifies that a hold with the given tag is applied recursively to the snapshots of all descendent file systems.

zfs holds [-r] snapshot...

    Lists all existing user references for the given snapshot or snapshots.

    -r

        Lists the holds that are set on the named descendent snapshots, in addition to listing the holds on the named snapshot.

zfs release [-r] tag snapshot...

    Removes a single reference, named with the tag argument, from the specified snapshot or snapshots. The tag must already exist for each snapshot.

    -r

        Recursively releases a hold with the given tag on the snapshots of all descendent file systems.

zfs diff [-FHt] snapshot snapshot|filesystem

    Display the difference between a snapshot of a given filesystem and another snapshot of that filesystem from a later time or the current contents of the filesystem. The first column is a character indicating the type of change, the other columns indicate pathname, new pathname (in case of rename), change in link count, and optionally file type and/or change time. The types of change are:
    -       The path has been removed
    +       The path has been created
    M       The path has been modified
    R       The path has been renamed

    -F

        Display an indication of the type of file, in a manner similar to the -F option of ls(1).
        B       Block device
        C       Character device
        /       Directory
        >       Door
        |       Named pipe
        @       Symbolic link
        P       Event port
        =       Socket
        F       Regular file

    -H

        Give more parsable tab-separated output, without header lines and without arrows.

    -t

        Display the path's inode change time as the first column of output.

EXAMPLES

Example 1 Creating a ZFS File System Hierarchy

The following commands create a file system named pool/home and a file system named pool/home/bob. The mount point /export/home is set for the parent file system, and is automatically inherited by the child file system.

# zfs create pool/home
# zfs set mountpoint=/export/home pool/home
# zfs create pool/home/bob

Example 2 Creating a ZFS Snapshot

The following command creates a snapshot named backup. This snapshot is mounted on demand in the .zfs/snapshot directory at the root of the pool/home/bob file system.

# zfs snapshot pool/home/bob@backup

Example 3 Creating and Destroying Multiple Snapshots

The following command creates snapshots named backup of pool/home and all of its descendent file systems. Each snapshot is mounted on demand in the .zfs/snapshot directory at the root of its file system. The second command destroys the newly created snapshots.

# zfs snapshot -r pool/home@backup
# zfs destroy -r pool/home@backup

Example 4 Disabling and Enabling File System Compression

The following command disables the compression property for all file systems under pool/home. The next command explicitly enables compression for pool/home/anne.

# zfs set compression=off pool/home
# zfs set compression=on pool/home/anne

Example 5 Listing ZFS Datasets

The following command lists all active file systems and volumes in the system. Snapshots are displayed if the pool's listsnapshots property is on (the default is off). See zpool(8) for more information on pool properties.

# zfs list
   NAME                      USED  AVAIL  REFER  MOUNTPOINT
   pool                      450K   457G    18K  /pool
   pool/home                 315K   457G    21K  /export/home
   pool/home/anne             18K   457G    18K  /export/home/anne
   pool/home/bob             276K   457G   276K  /export/home/bob

Example 6 Setting a Quota on a ZFS File System

The following command sets a quota of 50 GiB for pool/home/bob.

# zfs set quota=50G pool/home/bob

Example 7 Listing ZFS Properties

The following command lists all properties for pool/home/bob.

# zfs get all pool/home/bob
NAME           PROPERTY              VALUE                  SOURCE
pool/home/bob  type                  filesystem             -
pool/home/bob  creation              Tue Jul 21 15:53 2009  -
pool/home/bob  used                  21K                    -
pool/home/bob  available             20.0G                  -
pool/home/bob  referenced            21K                    -
pool/home/bob  compressratio         1.00x                  -
pool/home/bob  mounted               yes                    -
pool/home/bob  quota                 20G                    local
pool/home/bob  reservation           none                   default
pool/home/bob  recordsize            128K                   default
pool/home/bob  mountpoint            /pool/home/bob         default
pool/home/bob  sharenfs              off                    default
pool/home/bob  checksum              on                     default
pool/home/bob  compression           on                     local
pool/home/bob  atime                 on                     default
pool/home/bob  devices               on                     default
pool/home/bob  exec                  on                     default
pool/home/bob  setuid                on                     default
pool/home/bob  readonly              off                    default
pool/home/bob  zoned                 off                    default
pool/home/bob  snapdir               hidden                 default
pool/home/bob  acltype               off                    default
pool/home/bob  aclinherit            restricted             default
pool/home/bob  canmount              on                     default
pool/home/bob  xattr                 on                     default
pool/home/bob  copies                1                      default
pool/home/bob  version               4                      -
pool/home/bob  utf8only              off                    -
pool/home/bob  normalization         none                   -
pool/home/bob  casesensitivity       sensitive              -
pool/home/bob  vscan                 off                    default
pool/home/bob  nbmand                off                    default
pool/home/bob  sharesmb              off                    default
pool/home/bob  refquota              none                   default
pool/home/bob  refreservation        none                   default
pool/home/bob  primarycache          all                    default
pool/home/bob  secondarycache        all                    default
pool/home/bob  usedbysnapshots       0                      -
pool/home/bob  usedbydataset         21K                    -
pool/home/bob  usedbychildren        0                      -
pool/home/bob  usedbyrefreservation  0                      -
pool/home/bob  logbias               latency                default
pool/home/bob  dedup                 off                    default
pool/home/bob  mlslabel              none                   default
pool/home/bob  relatime              off                    default

The following command gets a single property value.

# zfs get -H -o value compression pool/home/bob
on

The following command lists all properties with local settings for pool/home/bob.

# zfs get -r -s local -o name,property,value all pool/home/bob
NAME           PROPERTY              VALUE
pool/home/bob  quota                 20G
pool/home/bob  compression           on

Example 8 Rolling Back a ZFS File System

The following command reverts the contents of pool/home/anne to the snapshot named yesterday, deleting all intermediate snapshots.

# zfs rollback -r pool/home/anne@yesterday

Example 9 Creating a ZFS Clone

The following command creates a writable file system whose initial contents are the same as pool/home/bob@yesterday.

# zfs clone pool/home/bob@yesterday pool/clone

Example 10 Promoting a ZFS Clone

The following commands illustrate how to test out changes to a file system, and then replace the original file system with the changed one, using clones, clone promotion, and renaming:

# zfs create pool/project/production
  populate /pool/project/production with data
# zfs snapshot pool/project/production@today
# zfs clone pool/project/production@today pool/project/beta
make changes to /pool/project/beta and test them
# zfs promote pool/project/beta
# zfs rename pool/project/production pool/project/legacy
# zfs rename pool/project/beta pool/project/production
once the legacy version is no longer needed, it can be destroyed
# zfs destroy pool/project/legacy

Example 11 Inheriting ZFS Properties

The following command causes pool/home/bob and pool/home/anne to inherit the checksum property from their parent.

# zfs inherit checksum pool/home/bob pool/home/anne

The following command causes pool/home/bob to revert to the received value for the quota property if it exists.

# zfs inherit -S quota pool/home/bob

Example 12 Remotely Replicating ZFS Data

The following commands send a full stream and then an incremental stream to a remote machine, restoring them into poolB/received/fs@aand poolB/received/fs@b, respectively. poolB must contain the file system poolB/received, and must not initially contain poolB/received/fs.

# zfs send pool/fs@a | \
   ssh host zfs receive poolB/received/fs@a
# zfs send -i a pool/fs@b | ssh host \
   zfs receive poolB/received/fs

Example 13 Using the zfs receive -d Option

The following command sends a full stream of poolA/fsA/fsB@snap to a remote machine, receiving it into poolB/received/fsA/fsB@snap. The fsA/fsB@snap portion of the received snapshot's name is determined from the name of the sent snapshot. poolB must contain the file system poolB/received. If poolB/received/fsA does not exist, it is created as an empty file system.

# zfs send poolA/fsA/fsB@snap | \
   ssh host zfs receive -d poolB/received

Example 14 Setting User Properties

The following example sets the user-defined com.example:department property for a dataset.

# zfs set com.example:department=12345 tank/accounting

Example 15 Performing a Rolling Snapshot

The following example shows how to maintain a history of snapshots with a consistent naming scheme. To keep a week's worth of snapshots, the user destroys the oldest snapshot, renames the remaining snapshots, and then creates a new snapshot, as follows:

# zfs destroy -r pool/users@7daysago
# zfs rename -r pool/users@6daysago @7daysago
# zfs rename -r pool/users@5daysago @6daysago
# zfs rename -r pool/users@4daysago @5daysago
# zfs rename -r pool/users@3daysago @4daysago
# zfs rename -r pool/users@2daysago @3daysago
# zfs rename -r pool/users@yesterday @2daysago
# zfs rename -r pool/users@today @yesterday
# zfs snapshot -r pool/users@today

Example 16 Setting sharenfs Property Options on a ZFS File System

The following commands show how to set sharenfs property options to enable rw access for a set of IP addresses and to enable root access for system neo on the tank/home file system.

# zfs set sharenfs='rw=@123.123.0.0/16,root=neo' tank/home

If you are using DNS for host name resolution, specify the fully qualified hostname.

Example 17 Delegating ZFS Administration Permissions on a ZFS Dataset

The following example shows how to set permissions so that user cindys can create, destroy, mount, and take snapshots on tank/cindys. The permissions on tank/cindys are also displayed.

# zfs allow cindys create,destroy,mount,snapshot tank/cindys
# zfs allow tank/cindys
-------------------------------------------------------------
Local+Descendent permissions on (tank/cindys)
          user cindys create,destroy,mount,snapshot
-------------------------------------------------------------

Because the tank/cindys mount point permission is set to 755 by default, user cindys will be unable to mount file systems under tank/cindys. Set an ACL similar to the following syntax to provide mount point access:

# chmod A+user:cindys:add_subdirectory:allow /tank/cindys

Example 18 Delegating Create Time Permissions on a ZFS Dataset

The following example shows how to grant anyone in the group staff to create file systems in tank/users. This syntax also allows staff members to destroy their own file systems, but not destroy anyone else's file system. The permissions on tank/users are also displayed.

# zfs allow staff create,mount tank/users
# zfs allow -c destroy tank/users
# zfs allow tank/users
-------------------------------------------------------------
Create time permissions on (tank/users)
          create,destroy
Local+Descendent permissions on (tank/users)
          group staff create,mount
-------------------------------------------------------------

Example 19 Defining and Granting a Permission Set on a ZFS Dataset

The following example shows how to define and grant a permission set on the tank/users file system. The permissions on tank/users are also displayed.

# zfs allow -s @pset create,destroy,snapshot,mount tank/users
# zfs allow staff @pset tank/users
# zfs allow tank/users
-------------------------------------------------------------
Permission sets on (tank/users)
        @pset create,destroy,mount,snapshot
Create time permissions on (tank/users)
        create,destroy
Local+Descendent permissions on (tank/users)
        group staff @pset,create,mount
-------------------------------------------------------------

Example 20 Delegating Property Permissions on a ZFS Dataset

The following example shows to grant the ability to set quotas and reservations on the users/home file system. The permissions on users/home are also displayed.

# zfs allow cindys quota,reservation users/home
# zfs allow users/home
-------------------------------------------------------------
Local+Descendent permissions on (users/home)
        user cindys quota,reservation
-------------------------------------------------------------
cindys% zfs set quota=10G users/home/marks
cindys% zfs get quota users/home/marks
NAME              PROPERTY  VALUE             SOURCE
users/home/marks  quota     10G               local

Example 21 Removing ZFS Delegated Permissions on a ZFS Dataset

The following example shows how to remove the snapshot permission from the staff group on the tank/users file system. The permissions on tank/users are also displayed.

# zfs unallow staff snapshot tank/users
# zfs allow tank/users
-------------------------------------------------------------
Permission sets on (tank/users)
        @pset create,destroy,mount,snapshot
Create time permissions on (tank/users)
        create,destroy
Local+Descendent permissions on (tank/users)
        group staff @pset,create,mount
-------------------------------------------------------------

Example 22 Showing the differences between a snapshot and a ZFS Dataset

The following example shows how to see what has changed between a prior snapshot of a ZFS Dataset and its current state. The -F option is used to indicate type information for the files affected.

# zfs diff -F tank/test@before tank/test
M       /       /tank/test/
M       F       /tank/test/linked      (+1)
R       F       /tank/test/oldname -> /tank/test/newname
-       F       /tank/test/deleted
+       F       /tank/test/created
M       F       /tank/test/modified

Example 23 Creating a bookmark

The following example create a bookmark to a snapshot. This bookmark can then be used instead of snapshot in send streams.

# zfs bookmark rpool@snapshot rpool#bookmark

ENVIRONMENT VARIABLES

ZFS_ABORT
    Cause zfs to dump core on exit for the purposes of running ::findleaks.

EXIT STATUS

The following exit values are returned:

0

    Successful completion.

1

    An error occurred.

2

    Invalid command line options were specified.

SEE ALSO

chmod(2), fsync(2), gzip(1), ls(1), mount(8), open(2), readdir(3), ssh(1), stat(2), write(2), zpool(8), zfs-module-parameters(5)

On Solaris: dfstab(4), iscsitadm(1M), mount(1M), share(1M), sharemgr(1M), unshare(1M)