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diff --git a/sys/contrib/openzfs/man/man7/zfsprops.7 b/sys/contrib/openzfs/man/man7/zfsprops.7 new file mode 100644 index 000000000000..3f3ddcebf320 --- /dev/null +++ b/sys/contrib/openzfs/man/man7/zfsprops.7 @@ -0,0 +1,2067 @@ +.\" +.\" CDDL HEADER START +.\" +.\" The contents of this file are subject to the terms of the +.\" Common Development and Distribution License (the "License"). +.\" You may not use this file except in compliance with the License. +.\" +.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE +.\" or http://www.opensolaris.org/os/licensing. +.\" See the License for the specific language governing permissions +.\" and limitations under the License. +.\" +.\" When distributing Covered Code, include this CDDL HEADER in each +.\" file and include the License file at usr/src/OPENSOLARIS.LICENSE. +.\" If applicable, add the following below this CDDL HEADER, with the +.\" fields enclosed by brackets "[]" replaced with your own identifying +.\" information: Portions Copyright [yyyy] [name of copyright owner] +.\" +.\" CDDL HEADER END +.\" +.\" Copyright (c) 2009 Sun Microsystems, Inc. All Rights Reserved. +.\" Copyright 2011 Joshua M. Clulow <josh@sysmgr.org> +.\" Copyright (c) 2011, 2019 by Delphix. All rights reserved. +.\" Copyright (c) 2011, Pawel Jakub Dawidek <pjd@FreeBSD.org> +.\" Copyright (c) 2012, Glen Barber <gjb@FreeBSD.org> +.\" Copyright (c) 2012, Bryan Drewery <bdrewery@FreeBSD.org> +.\" Copyright (c) 2013, Steven Hartland <smh@FreeBSD.org> +.\" Copyright (c) 2013 by Saso Kiselkov. All rights reserved. +.\" Copyright (c) 2014, Joyent, Inc. All rights reserved. +.\" Copyright (c) 2014 by Adam Stevko. All rights reserved. +.\" Copyright (c) 2014 Integros [integros.com] +.\" Copyright (c) 2016 Nexenta Systems, Inc. All Rights Reserved. +.\" Copyright (c) 2014, Xin LI <delphij@FreeBSD.org> +.\" Copyright (c) 2014-2015, The FreeBSD Foundation, All Rights Reserved. +.\" Copyright 2019 Richard Laager. All rights reserved. +.\" Copyright 2018 Nexenta Systems, Inc. +.\" Copyright 2019 Joyent, Inc. +.\" Copyright (c) 2019, Kjeld Schouten-Lebbing +.\" +.Dd May 24, 2021 +.Dt ZFSPROPS 7 +.Os +. +.Sh NAME +.Nm zfsprops +.Nd native and user-defined properties of ZFS datasets +. +.Sh DESCRIPTION +Properties are divided into two types, native properties and user-defined +.Po or +.Qq user +.Pc +properties. +Native properties either export internal statistics or control ZFS behavior. +In addition, native properties are either editable or read-only. +User properties have no effect on ZFS behavior, but you can use them to annotate +datasets in a way that is meaningful in your environment. +For more information about user properties, see the +.Sx User Properties +section, below. +. +.Ss Native Properties +Every dataset has a set of properties that export statistics about the dataset +as well as control various behaviors. +Properties are inherited from the parent unless overridden by the child. +Some properties apply only to certain types of datasets +.Pq file systems, volumes, or snapshots . +.Pp +The values of numeric properties can be specified using human-readable suffixes +.Po for example, +.Sy k , +.Sy KB , +.Sy M , +.Sy Gb , +and so forth, up to +.Sy Z +for zettabyte +.Pc . +The following are all valid +.Pq and equal +specifications: +.Li 1536M, 1.5g, 1.50GB . +.Pp +The values of non-numeric properties are case sensitive and must be lowercase, +except for +.Sy mountpoint , +.Sy sharenfs , +and +.Sy sharesmb . +.Pp +The following native properties consist of read-only statistics about the +dataset. +These properties can be neither set, nor inherited. +Native properties apply to all dataset types unless otherwise noted. +.Bl -tag -width "usedbyrefreservation" +.It Sy 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. +.Pp +This property can also be referred to by its shortened column name, +.Sy avail . +.It Sy compressratio +For non-snapshots, the compression ratio achieved for the +.Sy used +space of this dataset, expressed as a multiplier. +The +.Sy used +property includes descendant datasets, and, for clones, does not include the +space shared with the origin snapshot. +For snapshots, the +.Sy compressratio +is the same as the +.Sy refcompressratio +property. +Compression can be turned on by running: +.Nm zfs Cm set Sy compression Ns = Ns Sy on Ar dataset . +The default value is +.Sy off . +.It Sy createtxg +The transaction group (txg) in which the dataset was created. +Bookmarks have the same +.Sy createtxg +as the snapshot they are initially tied to. +This property is suitable for ordering a list of snapshots, +e.g. for incremental send and receive. +.It Sy creation +The time this dataset was created. +.It Sy clones +For snapshots, this property is a comma-separated list of filesystems or volumes +which are clones of this snapshot. +The clones' +.Sy origin +property is this snapshot. +If the +.Sy clones +property is not empty, then this snapshot can not be destroyed +.Po even with the +.Fl r +or +.Fl f +options +.Pc . +The roles of origin and clone can be swapped by promoting the clone with the +.Nm zfs Cm promote +command. +.It Sy defer_destroy +This property is +.Sy on +if the snapshot has been marked for deferred destroy by using the +.Nm zfs Cm destroy Fl d +command. +Otherwise, the property is +.Sy off . +.It Sy encryptionroot +For encrypted datasets, indicates where the dataset is currently inheriting its +encryption key from. +Loading or unloading a key for the +.Sy encryptionroot +will implicitly load / unload the key for any inheriting datasets (see +.Nm zfs Cm load-key +and +.Nm zfs Cm unload-key +for details). +Clones will always share an +encryption key with their origin. +See the +.Sx Encryption +section of +.Xr zfs-load-key 8 +for details. +.It Sy 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 +.Sy filesystem_limit +has been set somewhere in the tree under which the dataset resides. +.It Sy keystatus +Indicates if an encryption key is currently loaded into ZFS. +The possible values are +.Sy none , +.Sy available , +and +.Sy unavailable . +See +.Nm zfs Cm load-key +and +.Nm zfs Cm unload-key . +.It Sy guid +The 64 bit GUID of this dataset or bookmark which does not change over its +entire lifetime. +When a snapshot is sent to another pool, the received snapshot has the same GUID. +Thus, the +.Sy guid +is suitable to identify a snapshot across pools. +.It Sy logicalreferenced +The amount of space that is +.Qq logically +accessible by this dataset. +See the +.Sy referenced +property. +The logical space ignores the effect of the +.Sy compression +and +.Sy copies +properties, giving a quantity closer to the amount of data that applications +see. +However, it does include space consumed by metadata. +.Pp +This property can also be referred to by its shortened column name, +.Sy lrefer . +.It Sy logicalused +The amount of space that is +.Qq logically +consumed by this dataset and all its descendents. +See the +.Sy used +property. +The logical space ignores the effect of the +.Sy compression +and +.Sy copies +properties, giving a quantity closer to the amount of data that applications +see. +However, it does include space consumed by metadata. +.Pp +This property can also be referred to by its shortened column name, +.Sy lused . +.It Sy mounted +For file systems, indicates whether the file system is currently mounted. +This property can be either +.Sy yes +or +.Sy no . +.It Sy objsetid +A unique identifier for this dataset within the pool. +Unlike the dataset's +.Sy guid , No the Sy objsetid +of a dataset is not transferred to other pools when the snapshot is copied +with a send/receive operation. +The +.Sy objsetid +can be reused (for a new dataset) after the dataset is deleted. +.It Sy origin +For cloned file systems or volumes, the snapshot from which the clone was +created. +See also the +.Sy clones +property. +.It Sy receive_resume_token +For filesystems or volumes which have saved partially-completed state from +.Nm zfs Cm receive Fl s , +this opaque token can be provided to +.Nm zfs Cm send Fl t +to resume and complete the +.Nm zfs Cm receive . +.It Sy redact_snaps +For bookmarks, this is the list of snapshot guids the bookmark contains a redaction +list for. +For snapshots, this is the list of snapshot guids the snapshot is redacted with +respect to. +.It Sy 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. +.Pp +This property can also be referred to by its shortened column name, +.Sy refer . +.It Sy refcompressratio +The compression ratio achieved for the +.Sy referenced +space of this dataset, expressed as a multiplier. +See also the +.Sy compressratio +property. +.It Sy snapshot_count +The total number of snapshots that exist under this location in the dataset +tree. +This value is only available when a +.Sy snapshot_limit +has been set somewhere in the tree under which the dataset resides. +.It Sy type +The type of dataset: +.Sy filesystem , +.Sy volume , +.Sy snapshot , +or +.Sy bookmark . +.It Sy 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 is freed if this dataset is recursively destroyed, is the +greater of its space used and its reservation. +.Pp +The used space of a snapshot +.Po see the +.Sx Snapshots +section of +.Xr zfsconcepts 7 +.Pc +is space that is referenced exclusively by this snapshot. +If this snapshot is destroyed, the amount of +.Sy used +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 +.Sy used +space of a snapshot is a subset of the +.Sy written +space of the snapshot. +.Pp +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 +.Xr fsync 2 +or +.Sy O_SYNC +does not necessarily guarantee that the space usage information is updated +immediately. +.It Sy usedby* +The +.Sy usedby* +properties decompose the +.Sy used +properties into the various reasons that space is used. +Specifically, +.Sy used No = +.Sy usedbychildren No + +.Sy usedbydataset No + +.Sy usedbyrefreservation No + +.Sy usedbysnapshots . +These properties are only available for datasets created on +.Nm zpool +.Qo version 13 Qc +pools. +.It Sy usedbychildren +The amount of space used by children of this dataset, which would be freed if +all the dataset's children were destroyed. +.It Sy usedbydataset +The amount of space used by this dataset itself, which would be freed if the +dataset were destroyed +.Po after first removing any +.Sy refreservation +and destroying any necessary snapshots or descendents +.Pc . +.It Sy usedbyrefreservation +The amount of space used by a +.Sy refreservation +set on this dataset, which would be freed if the +.Sy refreservation +was removed. +.It Sy 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' +.Sy used +properties because space can be shared by multiple snapshots. +.It Sy userused Ns @ Ns Ar 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 +.Nm ls Fl l . +The amount of space charged is displayed by +.Nm du No and Nm ls Fl s . +See the +.Nm zfs Cm userspace +command for more information. +.Pp +Unprivileged users can access only their own space usage. +The root user, or a user who has been granted the +.Sy userused +privilege with +.Nm zfs Cm allow , +can access everyone's usage. +.Pp +The +.Sy userused Ns @ Ns Ar ... +properties are not displayed by +.Nm zfs Cm get Sy all . +The user's name must be appended after the +.Sy @ +symbol, using one of the following forms: +.Bl -bullet -compact -offset 4n +.It +POSIX name +.Pq Qq joe +.It +POSIX numeric ID +.Pq Qq 789 +.It +SID name +.Pq Qq joe.smith@mydomain +.It +SID numeric ID +.Pq Qq S-1-123-456-789 +.El +.Pp +Files created on Linux always have POSIX owners. +.It Sy userobjused Ns @ Ns Ar user +The +.Sy userobjused +property is similar to +.Sy userused +but instead it counts the number of objects consumed by a user. +This property counts all objects allocated on behalf of the user, +it may differ from the results of system tools such as +.Nm df Fl i . +.Pp +When the property +.Sy xattr Ns = Ns Sy on +is set on a file system additional objects will be created per-file to store +extended attributes. +These additional objects are reflected in the +.Sy userobjused +value and are counted against the user's +.Sy userobjquota . +When a file system is configured to use +.Sy xattr Ns = Ns Sy sa +no additional internal objects are normally required. +.It Sy userrefs +This property is set to the number of user holds on this snapshot. +User holds are set by using the +.Nm zfs Cm hold +command. +.It Sy groupused Ns @ Ns Ar 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 +.Nm ls Fl l . +See the +.Sy userused Ns @ Ns Ar user +property for more information. +.Pp +Unprivileged users can only access their own groups' space usage. +The root user, or a user who has been granted the +.Sy groupused +privilege with +.Nm zfs Cm allow , +can access all groups' usage. +.It Sy groupobjused Ns @ Ns Ar group +The number of objects consumed by the specified group in this dataset. +Multiple objects may be charged to the group for each file when extended +attributes are in use. +See the +.Sy userobjused Ns @ Ns Ar user +property for more information. +.Pp +Unprivileged users can only access their own groups' space usage. +The root user, or a user who has been granted the +.Sy groupobjused +privilege with +.Nm zfs Cm allow , +can access all groups' usage. +.It Sy projectused Ns @ Ns Ar project +The amount of space consumed by the specified project in this dataset. +Project is identified via the project identifier (ID) that is object-based +numeral attribute. +An object can inherit the project ID from its parent object (if the +parent has the flag of inherit project ID that can be set and changed via +.Nm chattr Fl /+P +or +.Nm zfs project Fl s ) +when being created. +The privileged user can set and change object's project +ID via +.Nm chattr Fl p +or +.Nm zfs project Fl s +anytime. +Space is charged to the project of each file, as displayed by +.Nm lsattr Fl p +or +.Nm zfs project . +See the +.Sy userused Ns @ Ns Ar user +property for more information. +.Pp +The root user, or a user who has been granted the +.Sy projectused +privilege with +.Nm zfs allow , +can access all projects' usage. +.It Sy projectobjused Ns @ Ns Ar project +The +.Sy projectobjused +is similar to +.Sy projectused +but instead it counts the number of objects consumed by project. +When the property +.Sy xattr Ns = Ns Sy on +is set on a fileset, ZFS will create additional objects per-file to store +extended attributes. +These additional objects are reflected in the +.Sy projectobjused +value and are counted against the project's +.Sy projectobjquota . +When a filesystem is configured to use +.Sy xattr Ns = Ns Sy sa +no additional internal objects are required. +See the +.Sy userobjused Ns @ Ns Ar user +property for more information. +.Pp +The root user, or a user who has been granted the +.Sy projectobjused +privilege with +.Nm zfs allow , +can access all projects' objects usage. +.It Sy volblocksize +For volumes, specifies the block size of the volume. +The +.Sy blocksize +cannot be changed once the volume has been written, so it should be set at +volume creation time. +The default +.Sy blocksize +for volumes is 8 Kbytes. +Any power of 2 from 512 bytes to 128 Kbytes is valid. +.Pp +This property can also be referred to by its shortened column name, +.Sy volblock . +.It Sy written +The amount of space +.Sy referenced +by this dataset, that was written since the previous snapshot +.Pq i.e. that is not referenced by the previous snapshot . +.It Sy written Ns @ Ns Ar snapshot +The amount of +.Sy 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. +.Pp +The +.Ar snapshot +may be specified as a short snapshot name +.Pq just the part after the Sy @ , +in which case it will be interpreted as a snapshot in the same filesystem as +this dataset. +The +.Ar snapshot +may be a full snapshot name +.Pq Ar filesystem Ns @ Ns Ar snapshot , +which for clones may be a snapshot in the origin's filesystem +.Pq or the origin of the origin's filesystem, etc. +.El +.Pp +The following native properties can be used to change the behavior of a ZFS +dataset. +.Bl -tag -width "" +.It Xo +.Sy aclinherit Ns = Ns Sy discard Ns | Ns Sy noallow Ns | Ns +.Sy restricted Ns | Ns Sy passthrough Ns | Ns Sy passthrough-x +.Xc +Controls how ACEs are inherited when files and directories are created. +.Bl -tag -compact -offset 4n -width "passthrough-x" +.It Sy discard +does not inherit any ACEs. +.It Sy noallow +only inherits inheritable ACEs that specify +.Qq deny +permissions. +.It Sy restricted +default, removes the +.Sy write_acl +and +.Sy write_owner +permissions when the ACE is inherited. +.It Sy passthrough +inherits all inheritable ACEs without any modifications. +.It Sy passthrough-x +same meaning as +.Sy passthrough , +except that the +.Sy owner@ , group@ , No and Sy everyone@ +ACEs inherit the execute permission only if the file creation mode also requests +the execute bit. +.El +.Pp +When the property value is set to +.Sy 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. +.Pp +The +.Sy aclinherit +property does not apply to POSIX ACLs. +.It Xo +.Sy aclmode Ns = Ns Sy discard Ns | Ns Sy groupmask Ns | Ns +.Sy passthrough Ns | Ns Sy restricted Ns +.Xc +Controls how an ACL is modified during chmod(2) and how inherited ACEs +are modified by the file creation mode: +.Bl -tag -compact -offset 4n -width "passthrough" +.It Sy discard +default, deletes all +.Sy ACEs +except for those representing +the mode of the file or directory requested by +.Xr chmod 2 . +.It Sy groupmask +reduces permissions granted in all +.Sy ALLOW +entries found in the +.Sy ACL +such that they are no greater than the group permissions specified by +.Xr chmod 2 . +.It Sy passthrough +indicates that no changes are made to the ACL other than creating or updating +the necessary ACL entries to represent the new mode of the file or directory. +.It Sy restricted +will cause the +.Xr chmod 2 +operation to return an error when used on any file or directory which has +a non-trivial ACL whose entries can not be represented by a mode. +.Xr chmod 2 +is required to change the set user ID, set group ID, or sticky bits on a file +or directory, as they do not have equivalent ACL entries. +In order to use +.Xr chmod 2 +on a file or directory with a non-trivial ACL when +.Sy aclmode +is set to +.Sy restricted , +you must first remove all ACL entries which do not represent the current mode. +.El +.It Sy acltype Ns = Ns Sy off Ns | Ns Sy nfsv4 Ns | Ns Sy posix +Controls whether ACLs are enabled and if so what type of ACL to use. +When this property is set to a type of ACL not supported by the current +platform, the behavior is the same as if it were set to +.Sy off . +.Bl -tag -compact -offset 4n -width "posixacl" +.It Sy off +default on Linux, when a file system has the +.Sy acltype +property set to off then ACLs are disabled. +.It Sy noacl +an alias for +.Sy off +.It Sy nfsv4 +default on +.Fx , +indicates that NFSv4-style ZFS ACLs should be used. +These ACLs can be managed with the +.Xr getfacl 1 +and +.Xr setfacl 1 . +The +.Sy nfsv4 +ZFS ACL type is not yet supported on Linux. +.It Sy posix +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 extended +attribute and therefore will not overwrite any existing NFSv4 ACLs which +may be set. +.It Sy posixacl +an alias for +.Sy posix +.El +.Pp +To obtain the best performance when setting +.Sy posix +users are strongly encouraged to set the +.Sy xattr Ns = Ns Sy sa +property. +This will result in the POSIX ACL being stored more efficiently on disk. +But as a consequence, all new extended attributes will only be +accessible from OpenZFS implementations which support the +.Sy xattr Ns = Ns Sy sa +property. +See the +.Sy xattr +property for more details. +.It Sy atime Ns = Ns Sy on Ns | Ns Sy off +Controls whether the access time for files is updated when they are read. +Turning this property 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 values +.Sy on +and +.Sy off +are equivalent to the +.Sy atime +and +.Sy noatime +mount options. +The default value is +.Sy on . +See also +.Sy relatime +below. +.It Sy canmount Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Sy noauto +If this property is set to +.Sy off , +the file system cannot be mounted, and is ignored by +.Nm zfs Cm mount Fl a . +Setting this property to +.Sy off +is similar to setting the +.Sy mountpoint +property to +.Sy none , +except that the dataset still has a normal +.Sy mountpoint +property, which can be inherited. +Setting this property to +.Sy off +allows datasets to be used solely as a mechanism to inherit properties. +One example of setting +.Sy canmount Ns = Ns Sy off +is to have two datasets with the same +.Sy mountpoint , +so that the children of both datasets appear in the same directory, but might +have different inherited characteristics. +.Pp +When set to +.Sy noauto , +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 +.Nm zfs Cm mount Fl a +command or unmounted by the +.Nm zfs Cm unmount Fl a +command. +.Pp +This property is not inherited. +.It Xo +.Sy checksum Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Sy fletcher2 Ns | Ns +.Sy fletcher4 Ns | Ns Sy sha256 Ns | Ns Sy noparity Ns | Ns +.Sy sha512 Ns | Ns Sy skein Ns | Ns Sy edonr +.Xc +Controls the checksum used to verify data integrity. +The default value is +.Sy on , +which automatically selects an appropriate algorithm +.Po currently, +.Sy fletcher4 , +but this may change in future releases +.Pc . +The value +.Sy off +disables integrity checking on user data. +The value +.Sy 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 +.Em NOT +a recommended practice. +.Pp +The +.Sy sha512 , +.Sy skein , +and +.Sy edonr +checksum algorithms require enabling the appropriate features on the pool. +.Fx +does not support the +.Sy edonr +algorithm. +.Pp +Please see +.Xr zpool-features 7 +for more information on these algorithms. +.Pp +Changing this property affects only newly-written data. +.It Xo +.Sy compression Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Sy gzip Ns | Ns +.Sy gzip- Ns Ar N Ns | Ns Sy lz4 Ns | Ns Sy lzjb Ns | Ns Sy zle Ns | Ns Sy zstd Ns | Ns +.Sy zstd- Ns Ar N Ns | Ns Sy zstd-fast Ns | Ns Sy zstd-fast- Ns Ar N +.Xc +Controls the compression algorithm used for this dataset. +.Pp +Setting compression to +.Sy 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, +.Sy 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 +.Sy lzjb +or, if the +.Sy lz4_compress +feature is enabled, +.Sy lz4 . +.Pp +The +.Sy lz4 +compression algorithm is a high-performance replacement for the +.Sy lzjb +algorithm. +It features significantly faster compression and decompression, as well as a +moderately higher compression ratio than +.Sy lzjb , +but can only be used on pools with the +.Sy lz4_compress +feature set to +.Sy enabled . +See +.Xr zpool-features 7 +for details on ZFS feature flags and the +.Sy lz4_compress +feature. +.Pp +The +.Sy lzjb +compression algorithm is optimized for performance while providing decent data +compression. +.Pp +The +.Sy gzip +compression algorithm uses the same compression as the +.Xr gzip 1 +command. +You can specify the +.Sy gzip +level by using the value +.Sy gzip- Ns Ar N , +where +.Ar N +is an integer from 1 +.Pq fastest +to 9 +.Pq best compression ratio . +Currently, +.Sy gzip +is equivalent to +.Sy gzip-6 +.Po which is also the default for +.Xr gzip 1 +.Pc . +.Pp +The +.Sy zstd +compression algorithm provides both high compression ratios and good performance. +You can specify the +.Sy zstd +level by using the value +.Sy zstd- Ns Ar N , +where +.Ar N +is an integer from 1 +.Pq fastest +to 19 +.Pq best compression ratio . +.Sy zstd +is equivalent to +.Sy zstd-3 . +.Pp +Faster speeds at the cost of the compression ratio can be requested by +setting a negative +.Sy zstd +level. +This is done using +.Sy zstd-fast- Ns Ar N , +where +.Ar N +is an integer in [1-9,10,20,30,...,100,500,1000] which maps to a negative +.Sy zstd +level. +The lower the level the faster the compression - +.Ar 1000 No provides the fastest compression and lowest compression ratio. +.Sy zstd-fast +is equivalent to +.Sy zstd-fast-1 . +.Pp +The +.Sy zle +compression algorithm compresses runs of zeros. +.Pp +This property can also be referred to by its shortened column name +.Sy compress . +Changing this property affects only newly-written data. +.Pp +When any setting except +.Sy off +is selected, compression will explicitly check for blocks consisting of only +zeroes (the NUL byte). +When a zero-filled block is detected, it is stored as +a hole and not compressed using the indicated compression algorithm. +.Pp +Any block being compressed must be no larger than 7/8 of its original size +after compression, otherwise the compression will not be considered worthwhile +and the block saved uncompressed. +Note that when the logical block is less than +8 times the disk sector size this effectively reduces the necessary compression +ratio; for example, 8kB blocks on disks with 4kB disk sectors must compress to 1/2 +or less of their original size. +.It Xo +.Sy context Ns = Ns Sy none Ns | Ns +.Ar SELinux-User : Ns Ar SElinux-Role : Ns Ar Selinux-Type : Ns Ar Sensitivity-Level +.Xc +This flag sets the SELinux context for all files in the file system under +a mount point for that file system. +See +.Xr selinux 8 +for more information. +.It Xo +.Sy fscontext Ns = Ns Sy none Ns | Ns +.Ar SELinux-User : Ns Ar SElinux-Role : Ns Ar Selinux-Type : Ns Ar Sensitivity-Level +.Xc +This flag sets the SELinux context for the file system file system being +mounted. +See +.Xr selinux 8 +for more information. +.It Xo +.Sy defcontext Ns = Ns Sy none Ns | Ns +.Ar SELinux-User : Ns Ar SElinux-Role : Ns Ar Selinux-Type : Ns Ar Sensitivity-Level +.Xc +This flag sets the SELinux default context for unlabeled files. +See +.Xr selinux 8 +for more information. +.It Xo +.Sy rootcontext Ns = Ns Sy none Ns | Ns +.Ar SELinux-User : Ns Ar SElinux-Role : Ns Ar Selinux-Type : Ns Ar Sensitivity-Level +.Xc +This flag sets the SELinux context for the root inode of the file system. +See +.Xr selinux 8 +for more information. +.It Sy copies Ns = Ns Sy 1 Ns | Ns Sy 2 Ns | Ns Sy 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 +.Sy used +property and counting against quotas and reservations. +.Pp +Changing this property only affects newly-written data. +Therefore, set this property at file system creation time by using the +.Fl o Sy copies Ns = Ns Ar N +option. +.Pp +Remember that ZFS will not import a pool with a missing top-level vdev. +Do +.Em NOT +create, for example a two-disk striped pool and set +.Sy copies Ns = Ns Ar 2 +on some datasets thinking you have setup redundancy for them. +When a disk fails you will not be able to import the pool +and will have lost all of your data. +.Pp +Encrypted datasets may not have +.Sy copies Ns = Ns Ar 3 +since the implementation stores some encryption metadata where the third copy +would normally be. +.It Sy devices Ns = Ns Sy on Ns | Ns Sy off +Controls whether device nodes can be opened on this file system. +The default value is +.Sy on . +The values +.Sy on +and +.Sy off +are equivalent to the +.Sy dev +and +.Sy nodev +mount options. +.It Xo +.Sy dedup Ns = Ns Sy off Ns | Ns Sy on Ns | Ns Sy verify Ns | Ns +.Sy sha256 Ns Oo , Ns Sy verify Oc Ns | Ns Sy sha512 Ns Oo , Ns Sy verify Oc Ns | Ns Sy skein Ns Oo , Ns Sy verify Oc Ns | Ns +.Sy edonr , Ns Sy verify +.Xc +Configures deduplication for a dataset. +The default value is +.Sy off . +The default deduplication checksum is +.Sy sha256 +(this may change in the future). +When +.Sy dedup +is enabled, the checksum defined here overrides the +.Sy checksum +property. +Setting the value to +.Sy verify +has the same effect as the setting +.Sy sha256 , Ns Sy verify . +.Pp +If set to +.Sy verify , +ZFS will do a byte-to-byte comparison in case of two blocks having the same +signature to make sure the block contents are identical. +Specifying +.Sy verify +is mandatory for the +.Sy edonr +algorithm. +.Pp +Unless necessary, deduplication should +.Em not +be enabled on a system. +See the +.Sx Deduplication +section of +.Xr zfsconcepts 7 . +.It Xo +.Sy dnodesize Ns = Ns Sy legacy Ns | Ns Sy auto Ns | Ns Sy 1k Ns | Ns +.Sy 2k Ns | Ns Sy 4k Ns | Ns Sy 8k Ns | Ns Sy 16k +.Xc +Specifies a compatibility mode or literal value for the size of dnodes in the +file system. +The default value is +.Sy legacy . +Setting this property to a value other than +.Sy legacy No requires the Sy large_dnode No pool feature to be enabled. +.Pp +Consider setting +.Sy dnodesize +to +.Sy auto +if the dataset uses the +.Sy xattr Ns = Ns Sy 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. +.Pp +Leave +.Sy dnodesize +set to +.Sy legacy +if you need to receive a send stream of this dataset on a pool that doesn't +enable the +.Sy large_dnode +feature, or if you need to import this pool on a system that doesn't support the +.Sy large_dnode No feature. +.Pp +This property can also be referred to by its shortened column name, +.Sy dnsize . +.It Xo +.Sy encryption Ns = Ns Sy off Ns | Ns Sy on Ns | Ns Sy aes-128-ccm Ns | Ns +.Sy aes-192-ccm Ns | Ns Sy aes-256-ccm Ns | Ns Sy aes-128-gcm Ns | Ns +.Sy aes-192-gcm Ns | Ns Sy aes-256-gcm +.Xc +Controls the encryption cipher suite (block cipher, key length, and mode) used +for this dataset. +Requires the +.Sy encryption +feature to be enabled on the pool. +Requires a +.Sy keyformat +to be set at dataset creation time. +.Pp +Selecting +.Sy encryption Ns = Ns Sy on +when creating a dataset indicates that the default encryption suite will be +selected, which is currently +.Sy aes-256-gcm . +In order to provide consistent data protection, encryption must be specified at +dataset creation time and it cannot be changed afterwards. +.Pp +For more details and caveats about encryption see the +.Sx Encryption +section of +.Xr zfs-load-key 8 . +.It Sy keyformat Ns = Ns Sy raw Ns | Ns Sy hex Ns | Ns Sy passphrase +Controls what format the user's encryption key will be provided as. +This property is only set when the dataset is encrypted. +.Pp +Raw keys and hex keys must be 32 bytes long (regardless of the chosen +encryption suite) and must be randomly generated. +A raw key can be generated with the following command: +.Dl # Nm dd Sy if=/dev/urandom bs=32 count=1 Sy of= Ns Pa /path/to/output/key +.Pp +Passphrases must be between 8 and 512 bytes long and will be processed through +PBKDF2 before being used (see the +.Sy pbkdf2iters +property). +Even though the encryption suite cannot be changed after dataset creation, +the keyformat can be with +.Nm zfs Cm change-key . +.It Xo +.Sy keylocation Ns = Ns Sy prompt Ns | Ns Sy file:// Ns Ar /absolute/file/path Ns | Ns Sy https:// Ns Ar address Ns | Ns Sy http:// Ns Ar address +.Xc +Controls where the user's encryption key will be loaded from by default for +commands such as +.Nm zfs Cm load-key +and +.Nm zfs Cm mount Fl l . +This property is only set for encrypted datasets which are encryption roots. +If unspecified, the default is +.Sy prompt . +.Pp +Even though the encryption suite cannot be changed after dataset creation, the +keylocation can be with either +.Nm zfs Cm set +or +.Nm zfs Cm change-key . +If +.Sy prompt +is selected ZFS will ask for the key at the command prompt when it is required +to access the encrypted data (see +.Nm zfs Cm load-key +for details). +This setting will also allow the key to be passed in via the standard input stream, +but users should be careful not to place keys which should be kept secret on +the command line. +If a file URI is selected, the key will be loaded from the +specified absolute file path. +If an HTTPS or HTTP URL is selected, it will be GETted using +.Xr fetch 3 , +libcurl, or nothing, depending on compile-time configuration and run-time availability. +The +.Sy SSL_CA_CERT_FILE +environment variable can be set to set the location +of the concatenated certificate store. +The +.Sy SSL_CA_CERT_PATH +environment variable can be set to override the location +of the directory containing the certificate authority bundle. +The +.Sy SSL_CLIENT_CERT_FILE +and +.Sy SSL_CLIENT_KEY_FILE +environment variables can be set to configure the path +to the client certificate and its key. +.It Sy pbkdf2iters Ns = Ns Ar iterations +Controls the number of PBKDF2 iterations that a +.Sy passphrase +encryption key should be run through when processing it into an encryption key. +This property is only defined when encryption is enabled and a keyformat of +.Sy passphrase +is selected. +The goal of PBKDF2 is to significantly increase the +computational difficulty needed to brute force a user's passphrase. +This is accomplished by forcing the attacker to run each passphrase through a +computationally expensive hashing function many times before they arrive at the +resulting key. +A user who actually knows the passphrase will only have to pay this cost once. +As CPUs become better at processing, this number should be +raised to ensure that a brute force attack is still not possible. +The current default is +.Sy 350000 +and the minimum is +.Sy 100000 . +This property may be changed with +.Nm zfs Cm change-key . +.It Sy exec Ns = Ns Sy on Ns | Ns Sy off +Controls whether processes can be executed from within this file system. +The default value is +.Sy on . +The values +.Sy on +and +.Sy off +are equivalent to the +.Sy exec +and +.Sy noexec +mount options. +.It Sy filesystem_limit Ns = Ns Ar count Ns | Ns Sy none +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 +.Sy filesystem_limit +to +.Sy on +a descendent of a filesystem that already has a +.Sy filesystem_limit +does not override the ancestor's +.Sy filesystem_limit , +but rather imposes an additional limit. +This feature must be enabled to be used +.Po see +.Xr zpool-features 7 +.Pc . +.It Sy special_small_blocks Ns = Ns Ar size +This value represents the threshold block size for including small file +blocks into the special allocation class. +Blocks smaller than or equal to this +value will be assigned to the special allocation class while greater blocks +will be assigned to the regular class. +Valid values are zero or a power of two from 512B up to 1M. +The default size is 0 which means no small file blocks +will be allocated in the special class. +.Pp +Before setting this property, a special class vdev must be added to the +pool. +See +.Xr zpoolconcepts 7 +for more details on the special allocation class. +.It Sy mountpoint Ns = Ns Pa path Ns | Ns Sy none Ns | Ns Sy legacy +Controls the mount point used for this file system. +See the +.Sx Mount Points +section of +.Xr zfsconcepts 7 +for more information on how this property is used. +.Pp +When the +.Sy 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 +.Sy legacy , +then they remain unmounted. +Otherwise, they are automatically remounted in the new location if the property +was previously +.Sy legacy +or +.Sy 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. +.It Sy nbmand Ns = Ns Sy on Ns | Ns Sy off +Controls whether the file system should be mounted with +.Sy nbmand +.Pq Non-blocking mandatory locks . +This is used for SMB clients. +Changes to this property only take effect when the file system is umounted and +remounted. +Support for these locks is scarce and not described by POSIX. +.It Sy overlay Ns = Ns Sy on Ns | Ns Sy off +Allow mounting on a busy directory or a directory which already contains +files or directories. +This is the default mount behavior for Linux and +.Fx +file systems. +On these platforms the property is +.Sy on +by default. +Set to +.Sy off +to disable overlay mounts for consistency with OpenZFS on other platforms. +.It Sy primarycache Ns = Ns Sy all Ns | Ns Sy none Ns | Ns Sy metadata +Controls what is cached in the primary cache +.Pq ARC . +If this property is set to +.Sy all , +then both user data and metadata is cached. +If this property is set to +.Sy none , +then neither user data nor metadata is cached. +If this property is set to +.Sy metadata , +then only metadata is cached. +The default value is +.Sy all . +.It Sy quota Ns = Ns Ar size Ns | Ns Sy none +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. +.Pp +Quotas cannot be set on volumes, as the +.Sy volsize +property acts as an implicit quota. +.It Sy snapshot_limit Ns = Ns Ar count Ns | Ns Sy none +Limits the number of snapshots that can be created on a dataset and its +descendents. +Setting a +.Sy snapshot_limit +on a descendent of a dataset that already has a +.Sy snapshot_limit +does not override the ancestor's +.Sy 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 +.Po see +.Xr zpool-features 7 +.Pc . +.It Sy userquota@ Ns Ar user Ns = Ns Ar size Ns | Ns Sy none +Limits the amount of space consumed by the specified user. +User space consumption is identified by the +.Sy userspace@ Ns Ar user +property. +.Pp +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 +.Er EDQUOT +error message. +See the +.Nm zfs Cm userspace +command for more information. +.Pp +Unprivileged users can only access their own groups' space usage. +The root user, or a user who has been granted the +.Sy userquota +privilege with +.Nm zfs Cm allow , +can get and set everyone's quota. +.Pp +This property is not available on volumes, on file systems before version 4, or +on pools before version 15. +The +.Sy userquota@ Ns Ar ... +properties are not displayed by +.Nm zfs Cm get Sy all . +The user's name must be appended after the +.Sy @ +symbol, using one of the following forms: +.Bl -bullet -compact -offset 4n +.It +POSIX name +.Pq Qq joe +.It +POSIX numeric ID +.Pq Qq 789 +.It +SID name +.Pq Qq joe.smith@mydomain +.It +SID numeric ID +.Pq Qq S-1-123-456-789 +.El +.Pp +Files created on Linux always have POSIX owners. +.It Sy userobjquota@ Ns Ar user Ns = Ns Ar size Ns | Ns Sy none +The +.Sy userobjquota +is similar to +.Sy userquota +but it limits the number of objects a user can create. +Please refer to +.Sy userobjused +for more information about how objects are counted. +.It Sy groupquota@ Ns Ar group Ns = Ns Ar size Ns | Ns Sy none +Limits the amount of space consumed by the specified group. +Group space consumption is identified by the +.Sy groupused@ Ns Ar group +property. +.Pp +Unprivileged users can access only their own groups' space usage. +The root user, or a user who has been granted the +.Sy groupquota +privilege with +.Nm zfs Cm allow , +can get and set all groups' quotas. +.It Sy groupobjquota@ Ns Ar group Ns = Ns Ar size Ns | Ns Sy none +The +.Sy groupobjquota +is similar to +.Sy groupquota +but it limits number of objects a group can consume. +Please refer to +.Sy userobjused +for more information about how objects are counted. +.It Sy projectquota@ Ns Ar project Ns = Ns Ar size Ns | Ns Sy none +Limits the amount of space consumed by the specified project. +Project space consumption is identified by the +.Sy projectused@ Ns Ar project +property. +Please refer to +.Sy projectused +for more information about how project is identified and set/changed. +.Pp +The root user, or a user who has been granted the +.Sy projectquota +privilege with +.Nm zfs allow , +can access all projects' quota. +.It Sy projectobjquota@ Ns Ar project Ns = Ns Ar size Ns | Ns Sy none +The +.Sy projectobjquota +is similar to +.Sy projectquota +but it limits number of objects a project can consume. +Please refer to +.Sy userobjused +for more information about how objects are counted. +.It Sy readonly Ns = Ns Sy on Ns | Ns Sy off +Controls whether this dataset can be modified. +The default value is +.Sy off . +The values +.Sy on +and +.Sy off +are equivalent to the +.Sy ro +and +.Sy rw +mount options. +.Pp +This property can also be referred to by its shortened column name, +.Sy rdonly . +.It Sy recordsize Ns = Ns Ar 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. +.Pp +For databases that create very large files but access them in small random +chunks, these algorithms may be suboptimal. +Specifying a +.Sy 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. +.Pp +The size specified must be a power of two greater than or equal to +.Ar 512B +and less than or equal to +.Ar 128kB . +If the +.Sy large_blocks +feature is enabled on the pool, the size may be up to +.Ar 1MB . +See +.Xr zpool-features 7 +for details on ZFS feature flags. +.Pp +Changing the file system's +.Sy recordsize +affects only files created afterward; existing files are unaffected. +.Pp +This property can also be referred to by its shortened column name, +.Sy recsize . +.It Sy redundant_metadata Ns = Ns Sy all Ns | Ns Sy 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 +.Pq e.g. by mirroring or RAID-Z , +and is in addition to an extra copy specified by the +.Sy copies +property +.Pq up to a total of 3 copies . +For example if the pool is mirrored, +.Sy copies Ns = Ns 2 , +and +.Sy redundant_metadata Ns = Ns Sy most , +then ZFS stores 6 copies of most metadata, and 4 copies of data and some +metadata. +.Pp +When set to +.Sy 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 +.Po which is +.Sy recordsize +bytes long +.Pc +can be lost. +.Pp +When set to +.Sy 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 +.Po of +.Sy recordsize +bytes each +.Pc +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. +.Pp +The default value is +.Sy all . +.It Sy refquota Ns = Ns Ar size Ns | Ns Sy none +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. +.It Sy refreservation Ns = Ns Ar size Ns | Ns Sy none Ns | Ns Sy auto +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 +.Sy refreservation . +The +.Sy refreservation +reservation is accounted for in the parent datasets' space used, and counts +against the parent datasets' quotas and reservations. +.Pp +If +.Sy 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 +.Qq referenced +bytes in the dataset. +.Pp +If +.Sy refreservation +is set to +.Sy auto , +a volume is thick provisioned +.Po or +.Qq not sparse +.Pc . +.Sy refreservation Ns = Ns Sy auto +is only supported on volumes. +See +.Sy volsize +in the +.Sx Native Properties +section for more information about sparse volumes. +.Pp +This property can also be referred to by its shortened column name, +.Sy refreserv . +.It Sy relatime Ns = Ns Sy on Ns | Ns Sy off +Controls the manner in which the access time is updated when +.Sy atime Ns = Ns Sy 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 +.Sy off . +The values +.Sy on +and +.Sy off +are equivalent to the +.Sy relatime +and +.Sy norelatime +mount options. +.It Sy reservation Ns = Ns Ar size Ns | Ns Sy none +The minimum amount of space guaranteed to a dataset and its descendants. +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. +.Pp +This property can also be referred to by its shortened column name, +.Sy reserv . +.It Sy secondarycache Ns = Ns Sy all Ns | Ns Sy none Ns | Ns Sy metadata +Controls what is cached in the secondary cache +.Pq L2ARC . +If this property is set to +.Sy all , +then both user data and metadata is cached. +If this property is set to +.Sy none , +then neither user data nor metadata is cached. +If this property is set to +.Sy metadata , +then only metadata is cached. +The default value is +.Sy all . +.It Sy setuid Ns = Ns Sy on Ns | Ns Sy off +Controls whether the setuid bit is respected for the file system. +The default value is +.Sy on . +The values +.Sy on +and +.Sy off +are equivalent to the +.Sy suid +and +.Sy nosuid +mount options. +.It Sy sharesmb Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Ar opts +Controls whether the file system is shared by using +.Sy Samba USERSHARES +and what options are to be used. +Otherwise, the file system is automatically shared and unshared with the +.Nm zfs Cm share +and +.Nm zfs Cm unshare +commands. +If the property is set to on, the +.Xr net 8 +command is invoked to create a +.Sy USERSHARE . +.Pp +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. +.Pp +If the +.Sy sharesmb +property is set to +.Sy off , +the file systems are unshared. +.Pp +The share is created with the ACL (Access Control List) "Everyone:F" ("F" +stands for "full permissions", i.e. 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 underlying file system. +.It Sy sharenfs Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Ar opts +Controls whether the file system is shared via NFS, and what options are to be +used. +A file system with a +.Sy sharenfs +property of +.Sy off +is managed with the +.Xr exportfs 8 +command and entries in the +.Pa /etc/exports +file. +Otherwise, the file system is automatically shared and unshared with the +.Nm zfs Cm share +and +.Nm zfs Cm unshare +commands. +If the property is set to +.Sy on , +the dataset is shared using the default options: +.Dl sec=sys,rw,crossmnt,no_subtree_check +.Pp +See +.Xr exports 5 +for the meaning of the default options. +Otherwise, the +.Xr exportfs 8 +command is invoked with options equivalent to the contents of this property. +.Pp +When the +.Sy 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 +.Sy off , +or if they were shared before the property was changed. +If the new property is +.Sy off , +the file systems are unshared. +.It Sy logbias Ns = Ns Sy latency Ns | Ns Sy throughput +Provide a hint to ZFS about handling of synchronous requests in this dataset. +If +.Sy logbias +is set to +.Sy latency +.Pq the default , +ZFS will use pool log devices +.Pq if configured +to handle the requests at low latency. +If +.Sy logbias +is set to +.Sy throughput , +ZFS will not use configured pool log devices. +ZFS will instead optimize synchronous operations for global pool throughput and +efficient use of resources. +.It Sy snapdev Ns = Ns Sy hidden Ns | Ns Sy visible +Controls whether the volume snapshot devices under +.Pa /dev/zvol/ Ns Aq Ar pool +are hidden or visible. +The default value is +.Sy hidden . +.It Sy snapdir Ns = Ns Sy hidden Ns | Ns Sy visible +Controls whether the +.Pa .zfs +directory is hidden or visible in the root of the file system as discussed in +the +.Sx Snapshots +section of +.Xr zfsconcepts 7 . +The default value is +.Sy hidden . +.It Sy sync Ns = Ns Sy standard Ns | Ns Sy always Ns | Ns Sy disabled +Controls the behavior of synchronous requests +.Pq e.g. fsync, O_DSYNC . +.Sy 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 +.Pq this is the default . +.Sy always +causes every file system transaction to be written and flushed before its +system call returns. +This has a large performance penalty. +.Sy 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. +.It Sy version Ns = Ns Ar N Ns | Ns Sy 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. +See the +.Nm zfs Cm upgrade +command. +.It Sy volsize Ns = Ns Ar size +For volumes, specifies the logical size of the volume. +By default, creating a volume establishes a reservation of equal size. +For storage pools with a version number of 9 or higher, a +.Sy refreservation +is set instead. +Any changes to +.Sy volsize +are reflected in an equivalent change to the reservation +.Pq or Sy refreservation . +The +.Sy volsize +can only be set to a multiple of +.Sy volblocksize , +and cannot be zero. +.Pp +The reservation is kept equal to the volume's logical size to prevent unexpected +behavior for consumers. +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 +.Pq particularly when shrinking the size . +Extreme care should be used when adjusting the volume size. +.Pp +Though not recommended, a +.Qq sparse volume +.Po also known as +.Qq thin provisioned +.Pc +can be created by specifying the +.Fl s +option to the +.Nm zfs Cm create Fl V +command, or by changing the value of the +.Sy refreservation +property +.Po or +.Sy reservation +property on pool version 8 or earlier +.Pc +after the volume has been created. +A +.Qq sparse volume +is a volume where the value of +.Sy refreservation +is less than the size of the volume plus the space required to store its +metadata. +Consequently, writes to a sparse volume can fail with +.Er ENOSPC +when the pool is low on space. +For a sparse volume, changes to +.Sy volsize +are not reflected in the +.Sy refreservation . +A volume that is not sparse is said to be +.Qq thick provisioned . +A sparse volume can become thick provisioned by setting +.Sy refreservation +to +.Sy auto . +.It Sy volmode Ns = Ns Sy default Ns | Ns Sy full Ns | Ns Sy geom Ns | Ns Sy dev Ns | Ns Sy none +This property specifies how volumes should be exposed to the OS. +Setting it to +.Sy full +exposes volumes as fully fledged block devices, providing maximal +functionality. +The value +.Sy geom +is just an alias for +.Sy full +and is kept for compatibility. +Setting it to +.Sy dev +hides its partitions. +Volumes with property set to +.Sy none +are not exposed outside ZFS, but can be snapshotted, cloned, replicated, etc, +that can be suitable for backup purposes. +Value +.Sy default +means that volumes exposition is controlled by system-wide tunable +.Sy zvol_volmode , +where +.Sy full , +.Sy dev +and +.Sy none +are encoded as 1, 2 and 3 respectively. +The default value is +.Sy full . +.It Sy vscan Ns = Ns Sy on Ns | Ns Sy off +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 +.Sy off . +This property is not used by OpenZFS. +.It Sy xattr Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Sy 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. +.Pp +The default value of +.Sy on +enables directory based extended attributes. +This style of extended attribute imposes no practical limit +on either the size or number of attributes which can be set on a file. +Although under Linux the +.Xr getxattr 2 +and +.Xr setxattr 2 +system calls limit the maximum size to 64K. +This is the most compatible +style of extended attribute and is supported by all ZFS implementations. +.Pp +System attribute based xattrs can be enabled by setting the value to +.Sy sa . +The key advantage of this type of xattr is improved performance. +Storing extended attributes as system attributes +significantly decreases the amount of disk IO required. +Up to 64K of data may be stored per-file in the space reserved for system attributes. +If there is not enough space available for an extended attribute +then it will be automatically written as a directory based xattr. +System attribute based extended attributes are not accessible +on platforms which do not support the +.Sy xattr Ns = Ns Sy sa +feature. +OpenZFS supports +.Sy xattr Ns = Ns Sy sa +on both +.Fx +and Linux. +.Pp +The use of system attribute based xattrs is strongly encouraged for users of +SELinux or POSIX ACLs. +Both of these features heavily rely on extended +attributes and benefit significantly from the reduced access time. +.Pp +The values +.Sy on +and +.Sy off +are equivalent to the +.Sy xattr +and +.Sy noxattr +mount options. +.It Sy jailed Ns = Ns Sy off Ns | Ns Sy on +Controls whether the dataset is managed from a jail. +See +.Xr zfs-jail 8 +for more information. +Jails are a +.Fx +feature and are not relevant on other platforms. +The default value is +.Sy off . +.It Sy zoned Ns = Ns Sy on Ns | Ns Sy off +Controls whether the dataset is managed from a non-global zone. +Zones are a Solaris feature and are not relevant on other platforms. +The default value is +.Sy off . +.El +.Pp +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 +.Nm zfs Cm create +or +.Nm zpool Cm 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. +.Bl -tag -width "" +.It Xo +.Sy casesensitivity Ns = Ns Sy sensitive Ns | Ns +.Sy insensitive Ns | Ns Sy mixed +.Xc +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 +.Sy casesensitivity +property is +.Sy sensitive . +Traditionally, +.Ux +and POSIX file systems have case-sensitive file names. +.Pp +The +.Sy mixed +value for the +.Sy 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 SMB server product. +For more information about the +.Sy mixed +value behavior, see the "ZFS Administration Guide". +.It Xo +.Sy normalization Ns = Ns Sy none Ns | Ns Sy formC Ns | Ns +.Sy formD Ns | Ns Sy formKC Ns | Ns Sy formKD +.Xc +Indicates whether the file system should perform a +.Sy unicode +normalization of file names whenever two file names are compared, and which +normalization algorithm should be used. +File names are always stored unmodified, names are normalized as part of any +comparison process. +If this property is set to a legal value other than +.Sy none , +and the +.Sy utf8only +property was left unspecified, the +.Sy utf8only +property is automatically set to +.Sy on . +The default value of the +.Sy normalization +property is +.Sy none . +This property cannot be changed after the file system is created. +.It Sy utf8only Ns = Ns Sy on Ns | Ns Sy off +Indicates whether the file system should reject file names that include +characters that are not present in the +.Sy UTF-8 +character code set. +If this property is explicitly set to +.Sy off , +the normalization property must either not be explicitly set or be set to +.Sy none . +The default value for the +.Sy utf8only +property is +.Sy off . +This property cannot be changed after the file system is created. +.El +.Pp +The +.Sy casesensitivity , +.Sy normalization , +and +.Sy utf8only +properties are also new permissions that can be assigned to non-privileged users +by using the ZFS delegated administration feature. +. +.Ss Temporary Mount Point Properties +When a file system is mounted, either through +.Xr mount 8 +for legacy mounts or the +.Nm zfs Cm 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: +.Bl -tag -compact -offset Ds -width "rootcontext=" +.It Sy atime +atime/noatime +.It Sy canmount +auto/noauto +.It Sy devices +dev/nodev +.It Sy exec +exec/noexec +.It Sy readonly +ro/rw +.It Sy relatime +relatime/norelatime +.It Sy setuid +suid/nosuid +.It Sy xattr +xattr/noxattr +.It Sy nbmand +mand/nomand +.It Sy context Ns = +context= +.It Sy fscontext Ns = +fscontext= +.It Sy defcontext Ns = +defcontext= +.It Sy rootcontext Ns = +rootcontext= +.El +.Pp +In addition, these options can be set on a per-mount basis using the +.Fl 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 +.Sy nosuid +option is an alias for +.Sy nodevices , Ns Sy nosetuid . +These properties are reported as +.Qq temporary +by the +.Nm zfs Cm get +command. +If the properties are changed while the dataset is mounted, the new setting +overrides any temporary settings. +. +.Ss 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 +.Pq file systems, volumes, and snapshots . +.Pp +User property names must contain a colon +.Pq Qq Sy \&: +character to distinguish them from native properties. +They may contain lowercase letters, numbers, and the following punctuation +characters: colon +.Pq Qq Sy \&: , +dash +.Pq Qq Sy - , +period +.Pq Qq Sy \&. , +and underscore +.Pq Qq Sy _ . +The expected convention is that the property name is divided into two portions +such as +.Ar module : Ns Ar property , +but this namespace is not enforced by ZFS. +User property names can be at most 256 characters, and cannot begin with a dash +.Pq Qq Sy - . +.Pp +When making programmatic use of user properties, it is strongly suggested to use +a reversed DNS domain name for the +.Ar module +component of property names to reduce the chance that two +independently-developed packages use the same property name for different +purposes. +.Pp +The values of user properties are arbitrary strings, are always inherited, and +are never validated. +All of the commands that operate on properties +.Po Nm zfs Cm list , +.Nm zfs Cm get , +.Nm zfs Cm set , +and so forth +.Pc +can be used to manipulate both native properties and user properties. +Use the +.Nm zfs Cm 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 8192 bytes. |