The \fBzfs\fR command configures \fBZFS\fR datasets within a \fBZFS\fR storage pool, as described in \fBzpool\fR(8). A dataset is identified by a unique path within the \fBZFS\fR namespace. For example:
A \fBZFS\fR dataset of type \fBfilesystem\fR can be mounted within the standard system namespace and behaves like other file systems. While \fBZFS\fR file systems are designed to be \fBPOSIX\fR 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.
.RE
.sp
.ne2
.na
\fB\fIvolume\fR\fR
.ad
.sp.6
.RS4n
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.
.RE
.sp
.ne2
.na
\fB\fIsnapshot\fR\fR
.ad
.sp.6
.RS4n
A read-only version of a file system or volume at a given point in time. It is specified as \fIfilesystem@name\fR or \fIvolume@name\fR.
A \fBZFS\fR storage pool is a logical collection of devices that provide space for datasets. A storage pool is also the root of the \fBZFS\fR 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 \fBzpool\fR(8) command.
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 \fBsnapdev\fR property of the parent volume.
File system snapshots can be accessed under the \fB\&.zfs/snapshot\fR 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 \fB\&.zfs\fR directory can be controlled by the \fBsnapdir\fR property.
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.
.sp
.LP
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.
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.
.sp
.LP
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 \fBorigin\fR property exposes this dependency, and the \fBdestroy\fR command lists any such dependencies, if they exist.
.sp
.LP
The clone parent-child dependency relationship can be reversed by using the \fBpromote\fR 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.
Creating a \fBZFS\fR file system is a simple operation, so the number of file systems per system is likely to be numerous. To cope with this, \fBZFS\fR automatically manages mounting and unmounting file systems without the need to edit the \fB/etc/fstab\fR file. All automatically managed file systems are mounted by \fBZFS\fR at boot time.
By default, file systems are mounted under \fB/\fIpath\fR\fR, where \fIpath\fR is the name of the file system in the \fBZFS\fR namespace. Directories are created and destroyed as needed.
A file system can also have a mount point set in the \fBmountpoint\fR property. This directory is created as needed, and \fBZFS\fR automatically mounts the file system when the \fBzfs mount -a\fR command is invoked (without editing \fB/etc/fstab\fR). The \fBmountpoint\fR property can be inherited, so if \fBpool/home\fR has a mount point of \fB/export/stuff\fR, then \fBpool/home/user\fR automatically inherits a mount point of \fB/export/stuff/user\fR.
If needed, \fBZFS\fR file systems can also be managed with traditional tools (\fBmount\fR, \fBumount\fR, \fB/etc/fstab\fR). If a file system's mount point is set to \fBlegacy\fR, \fBZFS\fR makes no attempt to manage the file system, and the administrator is responsible for mounting and unmounting the file system.
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 \fBdedup\fR property enabled, duplicate data blocks are removed synchronously. The result is that only unique data is stored and common components are shared among files.
Deduplicating data is a very resource-intensive operation. It is generally recommended that you have \fIat least\fR 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.
.sp
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.
.sp
Unless necessary, deduplication should NOT be enabled on a system. Instead, consider using \fIcompression=lz4\fR, as a less resource-intensive alternative.
Properties are divided into two types: native properties and user-defined (or "user") properties. Native properties either export internal statistics or control \fBZFS\fR behavior. User properties have no effect on \fBZFS\fR behavior, but you can use them to annotate datasets and snapshots in a way that is meaningful in your environment.
The values of numeric native properties can be specified using human-readable abbreviations (\fBK\fR, \fBM\fR, \fBG\fR, \fBT\fR, \fBP\fR, \fBE\fR, and \fBZ\fR). 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:
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.
.sp
This property can also be referred to by its shortened column name, \fBavail\fR.
For non-snapshots, the compression ratio achieved for the \fBused\fR space of this dataset, expressed as a multiplier. The \fBused\fR property includes descendant datasets, and, for clones, does not include the space shared with the origin snapshot. For snapshots, the \fBcompressratio\fR is the same as the \fBrefcompressratio\fR property. The \fBcompression\fR property controls whether compression is enabled on a dataset.
This property is \fBon\fR if the snapshot has been marked for deferred destruction by using the \fBzfs destroy\fR\fB-d\fR command. Otherwise, the property is \fBoff\fR.
For cloned file systems or volumes, the snapshot from which the clone was created. The origin cannot be destroyed (even with the \fB-r\fR or \fB-f\fR options) so long as a clone exists. See also the \fBclones\fR property.
For filesystems or volumes which have saved partially-completed state from \fBzfs receive -s\fR , this opaque token can be provided to \fBzfs send -t\fR to resume and complete the \fBzfs receive\fR.
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.
.sp
This property can also be referred to by its shortened column name, \fBrefer\fR.
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 is freed if this dataset is recursively destroyed, is the greater of its space used and its reservation.
The used space of a snapshot (see the "Snapshots" section) is space that is referenced exclusively by this snapshot. If this snapshot is destroyed, the amount of \fBused\fR space will be freed. Space that is shared by multiple snapshots isn't accounted for in this metric. When a snapshot is destroyed, space that was previously shared with this snapshot can become unique to snapshots adjacent to it, thus changing the used space of those snapshots. The used space of the latest snapshot can also be affected by changes in the file system. Note that the \fBused\fR space of a snapshot is a subset of the \fBwritten\fR space of the snapshot.
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 \fBfsync\fR(2) or \fBO_SYNC\fR (see \fBopen\fR(2)) does not necessarily guarantee that the space usage information is updated immediately.
The \fBusedby*\fR properties decompose the \fBused\fR properties into the various reasons that space is used. Specifically, \fBused\fR = \fBusedbychildren\fR + \fBusedbydataset\fR + \fBusedbyrefreservation\fR + \fBusedbysnapshots\fR. These properties are only available for datasets created on \fBzpool\fR version 13 or higher pools.
The amount of space used by children of this dataset, which would be freed if all the dataset's children were destroyed.
.RE
.sp
.ne2
.na
\fB\fBusedbydataset\fR\fR
.ad
.sp.6
.RS4n
The amount of space used by this dataset itself, which would be freed if the dataset were destroyed (after first removing any \fBrefreservation\fR and destroying any necessary snapshots or descendents).
.RE
.sp
.ne2
.na
\fB\fBusedbyrefreservation\fR\fR
.ad
.sp.6
.RS4n
The amount of space used by a \fBrefreservation\fR set on this dataset, which would be freed if the \fBrefreservation\fR was removed.
.RE
.sp
.ne2
.na
\fB\fBusedbysnapshots\fR\fR
.ad
.sp.6
.RS4n
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' \fBused\fR properties because space can be shared by multiple snapshots.
The amount of space consumed by the specified user in this dataset. Space is charged to the owner of each file, as displayed by \fBls\fR\fB-l\fR. The amount of space charged is displayed by \fBdu\fR and \fBls\fR\fB-s\fR. See the \fBzfs userspace\fR subcommand for more information.
.sp
Unprivileged users can access only their own space usage. The root user, or a user who has been granted the \fBuserused\fR privilege with \fBzfs allow\fR, can access everyone's usage.
.sp
The \fBuserused@\fR... properties are not displayed by \fBzfs get all\fR. The user's name must be appended after the \fB@\fR symbol, using one of the following forms:
.RS+4
.TP
.iet\(bu
.elo
\fIPOSIX name\fR (for example, \fBjoe\fR)
.RE
.RS+4
.TP
.iet\(bu
.elo
\fIPOSIX numeric ID\fR (for example, \fB789\fR)
.RE
.RS+4
.TP
.iet\(bu
.elo
\fISID name\fR (for example, \fBjoe.smith@mydomain\fR)
.RE
.RS+4
.TP
.iet\(bu
.elo
\fISID numeric ID\fR (for example, \fBS-1-123-456-789\fR)
The \fBuserobjused\fR is similar to \fBuserused\fR but instead it counts the number of objects consumed by \fIuser\fR. 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 \fBdfs -i\fR.
When the property \fBxattr=on\fR is set on a fileset, ZFS will create additional objects per-file to store extended attributes. These additional objects are reflected in the \fBuserobjused\fR value and are counted against the user's \fBuserobjquota\fR. When a filesystem is configured to use \fBxattr=sa\fR no additional internal objects are required.
The amount of space consumed by the specified group in this dataset. Space is charged to the group of each file, as displayed by \fBls\fR\fB-l\fR. See the \fBuserused@\fR\fIuser\fR property for more information.
.sp
Unprivileged users can only access their own groups' space usage. The root user, or a user who has been granted the \fBgroupused\fR privilege with \fBzfs allow\fR, can access all groups' usage.
The \fBgroupobjused\fR is similar to \fBgroupused\fR but instead it counts the number of objects consumed by \fIgroup\fR.
When the property \fBxattr=on\fR is set on a fileset, ZFS will create additional objects per-file to store extended attributes. These additional objects are reflected in the \fBgroupobjused\fR value and are counted against the group's \fBgroupobjquota.\fR. When a filesystem is configured to use \fBxattr=sa\fR no additional internal objects are required.
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.
.sp
This property cannot be changed after the volume is created.
Controls how \fBACL\fR entries are inherited when files and directories are created. A file system with an \fBaclinherit\fR property of \fBdiscard\fR does not inherit any \fBACL\fR entries. A file system with an \fBaclinherit\fR property value of \fBnoallow\fR only inherits inheritable \fBACL\fR entries that specify "deny" permissions. The property value \fBrestricted\fR (the default) removes the \fBwrite_acl\fR and \fBwrite_owner\fR permissions when the \fBACL\fR entry is inherited. A file system with an \fBaclinherit\fR property value of \fBpassthrough\fR inherits all inheritable \fBACL\fR entries without any modifications made to the \fBACL\fR entries when they are inherited. A file system with an \fBaclinherit\fR property value of \fBpassthrough-x\fR has the same meaning as \fBpassthrough\fR, except that the \fBowner@\fR, \fBgroup@\fR, and \fBeveryone@\fR\fBACE\fRs inherit the execute permission only if the file creation mode also requests the execute bit.
.sp
When the property value is set to \fBpassthrough\fR, files are created with a mode determined by the inheritable \fBACE\fRs. If no inheritable \fBACE\fRs exist that affect the mode, then the mode is set in accordance to the requested mode from the application.
Controls whether the access time for files is updated when they are read. Setting this property to \fBoff\fR 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 \fBon\fR. See also \fBrelatime\fR below.
.sp
The values \fBon\fR and \fBoff\fR are equivalent to the \fBatime\fR and \fBnoatime\fR mount options.
If this property is set to \fBoff\fR, the file system cannot be mounted, and is ignored by \fBzfs mount -a\fR. Setting this property to \fBoff\fR is similar to setting the \fBmountpoint\fR property to \fBnone\fR, except that the dataset still has a normal \fBmountpoint\fR property, which can be inherited. Setting this property to \fBoff\fR allows datasets to be used solely as a mechanism to inherit properties. One example of setting \fBcanmount=\fR\fBoff\fR is to have two datasets with the same \fBmountpoint\fR, so that the children of both datasets appear in the same directory, but might have different inherited characteristics.
.sp
When the \fBnoauto\fR 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 \fBzfs mount -a\fR command or unmounted by the \fBzfs unmount -a\fR command.
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 \fBused\fR property and counting against quotas and reservations.
Changing this property only affects newly-written data.
.sp
Remember that \fBZFS\fR will not import a pool with a missing top-level vdev. Do NOT create, for example, a two-disk, striped pool and set \fBcopies=\fR\fI2\fR 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.
Controls whether deduplication is in effect for a dataset. The default value is \fBoff\fR. The default checksum used for deduplication is \fBsha256\fR (subject to change). When \fBdedup\fR is enabled, the \fBdedup\fR checksum algorithm overrides the \fBchecksum\fR property. Setting the value to \fBverify\fR is equivalent to specifying \fBsha256,verify\fR.
.sp
If the property is set to \fBverify\fR, 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.
The \fBmlslabel\fR 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.
.sp
When the \fBmlslabel\fR property is not set, the default value is \fBnone\fR. Setting the \fBmlslabel\fR property to \fBnone\fR is equivalent to removing the property.
.sp
The \fBmlslabel\fR 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 \fB{PRIV_FILE_UPGRADE_SL}\fR privilege is required. When changing a label to a lower label or the default (\fBnone\fR), the \fB{PRIV_FILE_DOWNGRADE_SL}\fR 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 \fBmlslabel\fR property to the label of that zone.
.sp
When Trusted Extensions is \fBnot\fR enabled, only datasets with the default label (\fBnone\fR) can be mounted.
.sp
Zones are a Solaris feature and are not relevant on Linux.
When the \fBmountpoint\fR 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 \fBlegacy\fR, then they remain unmounted. Otherwise, they are automatically remounted in the new location if the property was previously \fBlegacy\fR or \fBnone\fR, or if they were mounted before the property was changed. In addition, any shared file systems are unshared and shared in the new location.
Controls whether the file system should be mounted with \fBnbmand\fR (Non Blocking mandatory locks). This is used for \fBCIFS\fR clients. Changes to this property only take effect when the file system is umounted and remounted. See \fBmount\fR(1M) on a Solaris system for more information on \fBnbmand\fR mounts.
.sp
The values \fBon\fR and \fBoff\fR are equivalent to the \fBnbmand\fR and \fBnonbmand\fR mount options.
Controls what is cached in the primary cache (ARC). If this property is set to \fBall\fR, then both user data and metadata is cached. If this property is set to \fBnone\fR, then neither user data nor metadata is cached. If this property is set to \fBmetadata\fR, then only metadata is cached. The default value is \fBall\fR.
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.
.sp
Quotas cannot be set on volumes, as the \fBvolsize\fR property acts as an implicit quota.
Limits the amount of space consumed by the specified user. Similar to the \fBrefquota\fR property, the \fBuserquota\fR space calculation does not include space that is used by descendent datasets, such as snapshots and clones. User space consumption is identified by the \fBuserspace@\fR\fIuser\fR property. See the \fBzfs userspace\fR 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 \fBEDQUOT\fR error message.
Unprivileged users can only access their own groups' space usage. The root user, or a user who has been granted the \fBuserquota\fR privilege with \fBzfs allow\fR, can get and set everyone's quota.
.sp
This property is not available on volumes, on file systems before version 4, or on pools before version 15. The \fBuserquota@\fR... properties are not displayed by \fBzfs get all\fR. The user's name must be appended after the \fB@\fR symbol, using one of the following forms:
.RS+4
.TP
.iet\(bu
.elo
\fIPOSIX name\fR (for example, \fBjoe\fR)
.RE
.RS+4
.TP
.iet\(bu
.elo
\fIPOSIX numeric ID\fR (for example, \fB789\fR)
.RE
.RS+4
.TP
.iet\(bu
.elo
\fISID name\fR (for example, \fBjoe.smith@mydomain\fR)
.RE
.RS+4
.TP
.iet\(bu
.elo
\fISID numeric ID\fR (for example, \fBS-1-123-456-789\fR)
Limits the amount of space consumed by the specified group. Group space consumption is identified by the \fBuserquota@\fR\fIuser\fR property.
.sp
Unprivileged users can access only their own groups' space usage. The root user, or a user who has been granted the \fBgroupquota\fR privilege with \fBzfs allow\fR, can get and set all groups' quotas.
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. \fBZFS\fR 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 \fBrecordsize\fR 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 \fBlarge_blocks\fR feature enabled. See \fBzpool-features\fR(5) for details on ZFS feature flags and the \fBlarge_blocks\fR feature.
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.
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 \fBrefreservation\fR. The \fBrefreservation\fR reservation is accounted for in the parent datasets' space used, and counts against the parent datasets' quotas and reservations.
If \fBrefreservation\fR is set, a snapshot is only allowed if there is enough free pool space outside of this reservation to accommodate the current number of \fBreferenced\fR bytes in the dataset (which are the bytes to be referenced by the snapshot). This is necessary to continue to provide the \fBrefreservation\fRguarantee to the dataset.
Controls the manner in which the access time is updated when \fBatime=on\fR is set. Turning this property \fBon\fR 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 \fBoff\fR.
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.
.sp
This property can also be referred to by its shortened column name, \fBreserv\fR.
Controls what is cached in the secondary cache (L2ARC). If this property is set to \fBall\fR, then both user data and metadata is cached. If this property is set to \fBnone\fR, then neither user data nor metadata is cached. If this property is set to \fBmetadata\fR, then only metadata is cached. The default value is \fBall\fR.
Controls whether the file system is shared by using \fBSamba USERSHARES\fR, and what options are to be used. Otherwise, the file system is automatically shared and unshared with the \fBzfs share\fR and \fBzfs unshare\fR commands. If the property is set to \fBon\fR, the \fBnet\fR(8) command is invoked to create a \fBUSERSHARE\fR.
Because \fBSMB\fR 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 (\fB_\fR) characters. Linux does not currently support additional options which might be available on Solaris.
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.
* 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.
.sp
* See the \fBUSERSHARE\fR section of the \fBsmb.conf\fR(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>.
Controls whether the file system is shared via \fBNFS\fR, and what options are used. A file system with a \fBsharenfs\fR property of \fBoff\fR is managed with the \fBexportfs\fR(8) command and entries in \fB/etc/exports\fR file. Otherwise, the file system is automatically shared and unshared with the \fBzfs share\fR and \fBzfs unshare\fR commands. If the property is set to \fBon\fR, the dataset is shared using the \fBexportfs\fR(8) command in the following manner (see \fBexportfs\fR(8) for the meaning of the different options):
.sp
.in+4
.nf
/usr/sbin/exportfs -i -o sec=sys,rw,no_subtree_check,no_root_squash,mountpoint *:<mountpoint of dataset>
.fi
.in-4
.sp
Otherwise, the \fBexportfs\fR(8) command is invoked with options equivalent to the contents of this property.
When the \fBsharenfs\fR 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 \fBoff\fR, or if they were shared before the property was changed. If the new property is \fBoff\fR, the file systems are unshared.
Provide a hint to ZFS about handling of synchronous requests in this dataset. If \fBlogbias\fR is set to \fBlatency\fR (the default), ZFS will use pool log devices (if configured) to handle the requests at low latency. If \fBlogbias\fR is set to \fBthroughput\fR, ZFS will not use configured pool log devices. ZFS will instead optimize synchronous operations for global pool throughput and efficient use of resources.
In this context, hidden does not refer to the concept of hiding files or directories by starting their name with a "." character. Even with \fBvisible\fR, the directory is still named \fB\&.zfs\fR. Instead, \fBhidden\fR means that the directory is not returned by \fBreaddir\fR(3), so it doesn't show up in directory listings done by any program, including \fBls\fR\fB-a\fR. It is still possible to chdir(2) into the directory, so \fBcd\fR\fB\&.zfs\fR works even with \fBhidden\fR. This unusual behavior is to protect against unwanted effects from applications recursing into the special \fB\&.zfs\fR directory.
Controls whether the \fB\&.zfs\fR directory is hidden or visible in the root of the file system as discussed in the "Snapshots" section. The default value is \fBhidden\fR.
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 \fBcurrent\fR automatically selects the latest supported version. See the \fBzfs upgrade\fR command.
For volumes, specifies the logical size of the volume. By default, creating a volume establishes a \fBrefreservation\fR equal to the volume size plus the metadata required for a fully-written volume. (For pool version 8 or lower, a \fBreservation\fR is set instead.) Any changes to \fBvolsize\fR are reflected in an equivalent change to the \fBrefreservation\fR. The \fBvolsize\fR can only be set to a multiple of \fBvolblocksize\fR, 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 \fB-s\fR option to the \fBzfs create -V\fR command, or by removing (or changing) the \fBrefreservation\fR after the volume has been created. A "sparse volume" is a volume where the \fBrefreservation\fR is unset or less then the volume size. Consequently, writes to a sparse volume can fail with \fBENOSPC\fR when the pool is low on space. For a sparse volume, changes to \fBvolsize\fR are not reflected in the reservation.
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 \fBoff\fR.
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 \fBoff\fR.
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 \fBzfs create\fR or \fBzpool create\fR 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.
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 \fBcasesensitivity\fR property is \fBsensitive\fR. Traditionally, UNIX and POSIX file systems have case-sensitive file names.
The \fBmixed\fR value for the \fBcasesensitivity\fR 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.
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.
.sp
If this property is set to a value other than \fBnone\fR (the default), and the \fButf8only\fR property was left unspecified, the \fButf8only\fR property is automatically set to \fBon\fR. See the cautionary note in the \fButf8only\fR section before modifying \fBnormalization\fR.
.sp
File names are always stored unmodified; names are normalized as part of any comparison process. Thus, \fBformC\fR and \fBformD\fR are equivalent, as are \fBformKC\fR and \fBformKD\fR. Given that, only \fBformD\fR and \fBformKD\fR make sense, as they are slightly faster because they avoid the additional canonical composition step.
.\" unicode.org says it's possible to quickly detect if a string is already in a given form. Since most text (basically everything but OS X) is already in NFC, this means formC could potentially be made faster. But the additional complexity probably isn't worth the likely undetectable in practice speed improvement.
.sp
The practical impact of this property is: \fBnone\fR (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,\fBformD\fR.
.sp
This property cannot be changed after the file system is created.
Indicates whether the file system should reject file names that include characters that are not present in the \fBUTF-8\fR character set. If this property is explicitly set to \fBoff\fR, the \fBnormalization\fR property must either not be explicitly set or be set to \fBnone\fR. The default value for the \fButf8only\fR property is \fBoff\fR.
.sp
Note that forcing the use of \fBUTF-8\fR 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.
.sp
If you are thinking of setting this (to \fBon\fR), you probably want to set \fBnormalization\fR=\fBformD\fR which will set this property to \fBon\fR implicitly.
.sp
This property cannot be changed after the file system is created.
The \fBcasesensitivity\fR, \fBnormalization\fR, and \fButf8only\fR properties are also permissions that can be assigned to non-privileged users by using the \fBZFS\fR delegated administration feature.
This flag sets the SELinux context for all files in the filesystem under the mountpoint for that filesystem. See \fBselinux\fR(8) for more information.
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 \fBoverlay=on\fR to enable overlay mounts.
When a file system is mounted, either through \fBmount\fR(8) for legacy mounts or the \fBzfs mount\fR command for normal file systems, its mount options are set according to its properties. The correlation between properties and mount options is as follows:
In addition, these options can be set on a per-mount basis using the \fB-o\fR 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 \fB-nosuid\fR option is an alias for \fBnodevices,nosetuid\fR. These properties are reported as "temporary" by the \fBzfs get\fR command. If the properties are changed while the dataset is mounted, the new setting overrides any temporary settings.
In addition to the standard native properties, \fBZFS\fR supports arbitrary user properties. User properties have no effect on \fBZFS\fR 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 (\fB:\fR) character to distinguish them from native properties. They may contain lowercase letters, numbers, and the following punctuation characters: colon (\fB:\fR), dash (\fB-\fR), period (\fB\&.\fR), and underscore (\fB_\fR). The expected convention is that the property name is divided into two portions such as \fImodule\fR\fB:\fR\fIproperty\fR, but this namespace is not enforced by \fBZFS\fR. User property names can be at most 256 characters, and cannot begin with a dash (\fB-\fR).
When making programmatic use of user properties, it is strongly suggested to use a reversed \fBDNS\fR domain name for the \fImodule\fR 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 \fBcom.sun\fR. 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 (\fBzfs list\fR, \fBzfs get\fR, \fBzfs set\fR, and so forth) can be used to manipulate both native properties and user properties. Use the \fBzfs inherit\fR 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.
Creates all the non-existing parent datasets. Datasets created in this manner inherit their properties; any property specified on the command line using the \fB-o\fR option applies only to the final child file system. If the target filesystem already exists, the operation completes successfully and no properties are changed.
Sets the specified property as if the command \fBzfs set\fR\fIproperty\fR=\fIvalue\fR was invoked at the same time the dataset was created. Any editable \fBZFS\fR property can also be set at creation time. Multiple \fB-o\fR options can be specified. An error results if the same property is specified in multiple \fB-o\fR options.
Creates a volume of the given size. The volume is exported as a block device in \fB/dev/zvol/\fR\fIpath\fR, where \fIpath\fR is the name of the volume in the \fBZFS\fR namespace. The size represents the logical size as exported by the device. By default, a \fBrefreservation\fR is created.
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 \fB-o\fR option applies only to the final child volume. If the target volume already exists, the operation completes successfully and no properties are changed.
Creates a sparse volume by omitting the automatic creation of a \fBrefreservation\fR. See \fBvolsize\fR in the Native Properties section for more information about sparse volumes. If this option is specified in conjunction with \fB-o\fR\fBrefreservation\fR, the \fBrefreservation\fR will be honored; this allows for a partial reservation on a sparse volume.
Sets the specified property as if the \fBzfs set\fR\fIproperty\fR=\fIvalue\fR command was invoked at the same time the dataset was created. Any editable \fBZFS\fR property can also be set at creation time. Multiple \fB-o\fR options can be specified. An error results if the same property is specified in multiple \fB-o\fR options.
Equivalent to \fB-o\fR\fBvolblocksize\fR=\fIblocksize\fR. If this option is specified in conjunction with \fB-o\fR\fBvolblocksize\fR, the resulting behavior is undefined.
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).
.sp
.ne2
.na
\fB\fB-r\fR\fR
.ad
.sp.6
.RS4n
Recursively destroy all children.
.RE
.sp
.ne2
.na
\fB\fB-R\fR\fR
.ad
.sp.6
.RS4n
Recursively destroy all dependents, including cloned file systems outside the target hierarchy.
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 \fBzfs hold\fR). If these conditions are not met, this command returns an error, unless \fB-d\fR is supplied.
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.
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.
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 \fB-r\fR option.
The \fB-rR\fR 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.
Creates a clone of the given snapshot. See the "Clones" section for details. The target dataset can be located anywhere in the \fBZFS\fR hierarchy, and is created as the same type as the original.
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 \fBzfs rename\fR command can be used to rename any conflicting snapshots.
Renames the given dataset. The new target can be located anywhere in the \fBZFS\fR 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.
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. \fBzfs list ./\fR). By default, all file systems and volumes are displayed. Snapshots are displayed if the pool's \fBlistsnapshots\fR property is \fBon\fR (the default is \fBoff\fR). 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 \fB-o name -s name\fR. The following fields are displayed by default: \fBname, used, available, referenced, mountpoint\fR
Recursively display any children of the dataset, limiting the recursion to \fIdepth\fR. A depth of \fB1\fR will display only the dataset and its direct children.
.RE
.sp
.ne2
.na
\fB\fB-o\fR\fIproperty\fR\fR
.ad
.sp.6
.RS4n
A comma-separated list of properties to display. The property must be:
.RS+4
.TP
.iet\(bu
.elo
One of the properties described in the "Native Properties" section
.RE
.RS+4
.TP
.iet\(bu
.elo
A user property
.RE
.RS+4
.TP
.iet\(bu
.elo
The value \fBname\fR to display the dataset name
.RE
.RS+4
.TP
.iet\(bu
.elo
The value \fBspace\fR to display space usage properties on file systems and volumes. This is a shortcut for specifying \fB-o name,avail,used,usedsnap,usedds,usedrefreserv,usedchild\fR\fB-t filesystem,volume\fR syntax.
.RE
.RE
.sp
.ne2
.na
\fB\fB-s\fR\fIproperty\fR\fR
.ad
.sp.6
.RS4n
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 \fBname\fR to sort by the dataset name. Multiple properties can be specified at one time using multiple \fB-s\fR property options. Multiple \fB-s\fR options are evaluated from left to right in decreasing order of importance.
.sp
The following is a list of sorting criteria:
.RS+4
.TP
.iet\(bu
.elo
Numeric types sort in numeric order.
.RE
.RS+4
.TP
.iet\(bu
.elo
String types sort in alphabetical order.
.RE
.RS+4
.TP
.iet\(bu
.elo
Types inappropriate for a row sort that row to the literal bottom, regardless of the specified ordering.
.RE
.RS+4
.TP
.iet\(bu
.elo
If no sorting options are specified the existing behavior of \fBzfs list\fR is preserved.
A comma-separated list of types to display, where \fItype\fR is one of \fBfilesystem\fR, \fBsnapshot\fR, \fBsnap\fR, \fBvolume\fR, \fBbookmark\fR, or \fBall\fR. For example, specifying \fB-t snapshot\fR displays only snapshots.
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:
.sp
.in+2
.nf
name Dataset name
property Property name
value Property value
source Property source. Can either be local, default,
All columns are displayed by default, though this can be controlled by using the \fB-o\fR option. This command takes a comma-separated list of properties as described in the "Native Properties" and "User Properties" sections.
Recursively display any children of the dataset, limiting the recursion to \fIdepth\fR. A depth of \fB1\fR will display only the dataset and its direct children.
.RE
.sp
.ne2
.na
\fB\fB-H\fR\fR
.ad
.sp.6
.RS4n
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.
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: \fBlocal,default,inherited,received,temporary,none\fR. The default value is all sources.
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 \fB-S\fR 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.
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. \fBzfs send\fR streams generated from new snapshots of these file systems cannot be accessed on systems running older versions of the software.
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.
Upgrades to the specified \fIversion\fR. If the \fB-V\fR 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.
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.
Allow mounting the filesystem even if the target directory is not empty.
.sp
On Solaris, the behavior of \fBzfs mount\fR matches \fBmount\fR and \fBzfs mount -O\fR matches \fBmount -O\fR. See \fBmount\fR(1M).
.sp
On Linux, this is the default for \fBmount\fR(8). In other words, \fBzfs mount -O\fR matches \fBmount\fR and there is no \fBmount\fR equivalent to a plain \fBzfs mount\fR.
Share all available \fBZFS\fR file systems. Invoked automatically as part of the boot process. Additionally if one of \fBnfs\fR|\fBsmb\fR protocols is specified only share file systems whose \fBsharenfs\fR|\fBsharesmb\fR is set.
Share the specified filesystem according to the \fBsharenfs\fR and \fBsharesmb\fR properties. File systems are shared when the \fBsharenfs\fR or \fBsharesmb\fR property is set.
Unshares currently shared \fBZFS\fR file systems. This is invoked automatically as part of the shutdown process. Additionally if one of \fBnfs\fR|\fBsmb\fR is specified unshare only file systems currently shared by that protocol.
Creates a stream representation of the (second, if \fB-i\fR is specified) \fIsnapshot\fR, which is written to standard output. The output can be redirected to a file or to a pipe (for example, using \fBssh\fR(1) to send it to a different system with \fBzfs receive\fR). By default, a full stream is generated; specifying \fB-i\fR or \fB-I\fR changes this behavior.
Generate an incremental stream from the first \fIsnapshot\fR (the incremental source) to the second \fIsnapshot\fR (the incremental target). The incremental source can be specified as the last component of the snapshot name (the \fB@\fR 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, \fBpool/fs@origin\fR, not just \fB@origin\fR).
Generate a stream package that sends all intermediary snapshots from the first snapshot to the second snapshot. For example, \fB-I @a fs@d\fR is similar to \fB-i @a fs@b; -i @b fs@c; -i @c fs@d\fR. The incremental source may be specified as with the \fB-i\fR option.
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 \fB-i\fR or \fB-I\fR flags are used in conjunction with the \fB-R\fR 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 \fB-F\fR flag is specified when this stream is received, snapshots and file systems that do not exist on the sending side are destroyed.
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).
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 \fB#\fR or \fB@\fR character and following).
.sp
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.
Creates a send stream which resumes an interrupted receive. The \fIreceive_resume_token\fR is the value of this property on the filesystem or volume that was being received into. See the documentation for \fBzfs receive -s\fR for more details.
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 \fBzfs send\fR subcommand, which by default creates a full stream. \fBzfs recv\fR can be used as an alias for \fBzfs receive\fR.
.sp
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 \fBzvols\fR, the destination device link is destroyed and recreated, which means the \fBzvol\fR cannot be accessed during the \fBreceive\fR operation.
When a snapshot replication package stream that is generated by using the \fBzfs send\fR\fB-R\fR command is received, any snapshots that do not exist on the sending location are destroyed by using the \fBzfs destroy\fR\fB-d\fR 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 \fB-d\fR or \fB-e\fR options.
If the argument is a snapshot name, the specified \fIsnapshot\fR 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 \fIfilesystem\fR or \fIvolume\fR. If neither of the \fB-d\fR or \fB-e\fR options are specified, the provided target snapshot name is used exactly as provided.
.sp
The \fB-d\fR and \fB-e\fR 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 \fIfilesystem\fR. If the \fB-d\fR 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 \fB-e\fR 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.
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 \fBzfs send -R -[iI]\fR), destroy snapshots and file systems that do not exist on the sending side.
Do not actually receive the stream. This can be useful in conjunction with the \fB-v\fR option to verify the name the receive operation would use.
.RE
.sp
.ne2
.na
\fB\fB-s\fR\fR
.ad
.sp.6
.RS4n
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 \fBzfs receive\fR process, or unclean shutdown of the system.
.sp
The receive can be resumed with a stream generated by \fBzfs send -t\fR token, where the \fItoken\fR is the value of the \fBreceive_resume_token\fR property of the filesystem or volume which is received into.
.sp
To use this flag, the storage pool must have the \fBextensible_dataset\fR feature enabled. See \fBzpool-features\fR(5) for details on ZFS feature flags.
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.
.RE
.sp
.ne2
.na
\fB\fB-e\fR\fR
.ad
.sp.6
.RS4n
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.
Specifies to whom the permissions are delegated. Multiple entities can be specified as a comma-separated list. If neither of the \fB-ug\fR 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 \fB-u\fR or \fB-g\fR options. To specify a group with the same name as a user, use the \fB-g\fR options.
.RE
.sp
.ne2
.na
\fB[\fB-e\fR] \fIperm\fR|@\fIsetname\fR[,...]\fR
.ad
.sp.6
.RS4n
Specifies that the permissions be delegated to "everyone." Multiple permissions may be specified as a comma-separated list. Permission names are the same as \fBZFS\fR subcommand and property names. See the property list below. Property set names, which begin with an at sign (\fB@\fR) , may be specified. See the \fB-s\fR form below for details.
.RE
.sp
.ne2
.na
\fB[\fB-ld\fR] \fIfilesystem\fR|\fIvolume\fR\fR
.ad
.sp.6
.RS4n
Specifies where the permissions are delegated. If neither of the \fB-ld\fR 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 \fB-l\fR option is used, then is allowed "locally" only for the specified file system. If only the \fB-d\fR option is used, then is allowed only for the descendent file systems.
Defines or adds permissions to a permission set. The set can be used by other \fBzfs allow\fR 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" (\fB@\fR), and can be no more than 64 characters long.
Removes permissions that were granted with the \fBzfs allow\fR 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 \fIuser\fR, \fIgroup\fR, or \fIeveryone\fR are removed. Specifying "everyone" (or using the \fB-e\fR option) only removes the permissions that were granted to "everyone", not all permissions for every user and group. See the \fBzfs allow\fR command for a description of the \fB-ldugec\fR options.
.sp
.ne2
.na
\fB\fB-r\fR\fR
.ad
.sp.6
.RS4n
Recursively remove the permissions from this file system and all descendents.
Adds a single reference, named with the \fItag\fR argument, to the specified snapshot or snapshots. Each snapshot has its own tag namespace, and tags must be unique within that space.
.sp
If a hold exists on a snapshot, attempts to destroy that snapshot by using the \fBzfs destroy\fR command return \fBEBUSY\fR.
.sp
.ne2
.na
\fB\fB-r\fR\fR
.ad
.sp.6
.RS4n
Specifies that a hold with the given tag is applied recursively to the snapshots of all descendent file systems.
\fBExample 1 \fRCreating a ZFS File System Hierarchy
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The following commands create a file system named \fBpool/home\fR and a file system named \fBpool/home/bob\fR. The mount point \fB/export/home\fR is set for the parent file system, and is automatically inherited by the child file system.
The following command creates a snapshot named \fBbackup\fR. This snapshot is mounted on demand in the \fB\&.zfs/snapshot\fR directory at the root of the \fBpool/home/bob\fR file system.
The following command creates snapshots named \fBbackup\fR of \fBpool/home\fR and all of its descendent file systems. Each snapshot is mounted on demand in the \fB\&.zfs/snapshot\fR directory at the root of its file system. The second command destroys the newly created snapshots.
\fBExample 4 \fRDisabling and Enabling File System Compression
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The following command disables the \fBcompression\fR property for all file systems under \fBpool/home\fR. The next command explicitly enables \fBcompression\fR for \fBpool/home/anne\fR.
The following command lists all active file systems and volumes in the system. Snapshots are displayed if the pool's \fBlistsnapshots\fR property is \fBon\fR (the default is \fBoff\fR). See \fBzpool\fR(8) for more information on pool properties.
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:
The following commands send a full stream and then an incremental stream to a remote machine, restoring them into \fBpoolB/received/fs@a\fRand \fBpoolB/received/fs@b\fR, respectively. \fBpoolB\fR must contain the file system \fBpoolB/received\fR, and must not initially contain \fBpoolB/received/fs\fR.
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# \fBzfs send pool/fs@a | \e\fR
\fBssh host zfs receive poolB/received/fs@a\fR
# \fBzfs send -i a pool/fs@b | ssh host \e\fR
\fBzfs receive poolB/received/fs\fR
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\fBExample 13 \fRUsing the \fBzfs receive\fR\fB-d\fR Option
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The following command sends a full stream of \fBpoolA/fsA/fsB@snap\fR to a remote machine, receiving it into \fBpoolB/received/fsA/fsB@snap\fR. The \fBfsA/fsB@snap\fR portion of the received snapshot's name is determined from the name of the sent snapshot. \fBpoolB\fR must contain the file system \fBpoolB/received\fR. If \fBpoolB/received/fsA\fR does not exist, it is created as an empty file system.
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# \fBzfs send poolA/fsA/fsB@snap | \e
ssh host zfs receive -d poolB/received\fR
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\fBExample 14 \fRSetting User Properties
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The following example sets the user-defined \fBcom.example:department\fR property for a dataset.
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# \fBzfs set com.example:department=12345 tank/accounting\fR
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:
The following commands show how to set \fBsharenfs\fR property options to enable \fBrw\fR access for a set of \fBIP\fR addresses and to enable root access for system \fBneo\fR on the \fBtank/home\fR file system.
The following example shows how to set permissions so that user \fBcindys\fR can create, destroy, mount, and take snapshots on \fBtank/cindys\fR. The permissions on \fBtank/cindys\fR are also displayed.
Because the \fBtank/cindys\fR mount point permission is set to 755 by default, user \fBcindys\fR will be unable to mount file systems under \fBtank/cindys\fR. Set an \fBACL\fR similar to the following syntax to provide mount point access:
The following example shows how to grant anyone in the group \fBstaff\fR to create file systems in \fBtank/users\fR. This syntax also allows staff members to destroy their own file systems, but not destroy anyone else's file system. The permissions on \fBtank/users\fR are also displayed.
The following example shows how to define and grant a permission set on the \fBtank/users\fR file system. The permissions on \fBtank/users\fR are also displayed.
The following example shows to grant the ability to set quotas and reservations on the \fBusers/home\fR file system. The permissions on \fBusers/home\fR are also displayed.
The following example shows how to remove the snapshot permission from the \fBstaff\fR group on the \fBtank/users\fR file system. The permissions on \fBtank/users\fR are also displayed.
