This section describes how ZFS mounts file systems.
By default, a ZFS file system is automatically mounted when it is created. You can determine specific mount-point behavior for a file system as described in this section.
You can also set the default mount point for a pool's file system at creation time by using zpool create's –m option. For more information about creating pools, see Creating ZFS Storage Pools.
All ZFS file systems are mounted by ZFS at boot time by using the Service Management Facility's (SMF) svc://system/filesystem/local service. File systems are mounted under /path, where path is the name of the file system.
You can override the default mount point by using the zfs set command to set the mountpoint property to a specific path. ZFS automatically creates the specified mount point, if needed, and automatically mounts the associated file system.
ZFS file systems are automatically mounted at boot time without requiring you to edit the /etc/vfstab file.
The mountpoint property is inherited. For example, if pool/home has the mountpoint property set to /export/stuff, then pool/home/user inherits /export/stuff/user for its mountpoint property value.
To prevent a file system from being mounted, set the mountpoint property to none. In addition, the canmount property can be used to control whether a file system can be mounted. For more information about the canmount property, see The canmount Property.
File systems can also be explicitly managed through legacy mount interfaces by using zfs set to set the mountpoint property to legacy. Doing so prevents ZFS from automatically mounting and managing a file system. Legacy tools including the mount and umount commands, and the /etc/vfstab file must be used instead. For more information about legacy mounts, see Legacy Mount Points.
When you change the mountpoint property from legacy or none to a specific path, ZFS automatically mounts the file system.
If ZFS is managing a file system but it is currently unmounted, and the mountpoint property is changed, the file system remains unmounted.
Any file system whose mountpoint property is not legacy is managed by ZFS. In the following example, a file system is created whose mount point is automatically managed by ZFS:
# zfs create pool/filesystem # zfs get mountpoint pool/filesystem NAME PROPERTY VALUE SOURCE pool/filesystem mountpoint /pool/filesystem default # zfs get mounted pool/filesystem NAME PROPERTY VALUE SOURCE pool/filesystem mounted yes -
You can also explicitly set the mountpoint property as shown in the following example:
# zfs set mountpoint=/mnt pool/filesystem # zfs get mountpoint pool/filesystem NAME PROPERTY VALUE SOURCE pool/filesystem mountpoint /mnt local # zfs get mounted pool/filesystem NAME PROPERTY VALUE SOURCE pool/filesystem mounted yes -
When the mountpoint property is changed, the file system is automatically unmounted from the old mount point and remounted to the new mount point. Mount-point directories are created as needed. If ZFS is unable to unmount a file system due to it being active, an error is reported, and a forced manual unmount is necessary.
You can manage ZFS file systems with legacy tools by setting the mountpoint property to legacy. Legacy file systems must be managed through the mount and umount commands and the /etc/vfstab file. ZFS does not automatically mount legacy file systems at boot time, and the ZFS mount and umount commands do not operate on file systems of this type. The following examples show how to set up and manage a ZFS file system in legacy mode:
# zfs set mountpoint=legacy tank/home/eric # mount -F zfs tank/home/eschrock /mnt
To automatically mount a legacy file system at boot time, you must add an entry to the /etc/vfstab file. The following example shows what the entry in the /etc/vfstab file might look like:
#device device mount FS fsck mount mount #to mount to fsck point type pass at boot options # tank/home/eric - /mnt zfs - yes -
The device to fsck and fsck pass entries are set to - because the fsck command is not applicable to ZFS file systems.
ZFS automatically mounts file systems when file systems are created or when the system boots. Use of the zfs mount command is necessary only when you need to change mount options, or explicitly mount or unmount file systems.
The zfs mount command with no arguments shows all currently mounted file systems that are managed by ZFS. Legacy managed mount points are not displayed. For example:
# zfs mount | grep tank/home zfs mount | grep tank/home tank/home /tank/home tank/home/jeff /tank/home/jeff
You can use the –a option to mount all ZFS managed file systems. Legacy managed file systems are not mounted. For example:
# zfs mount -a
By default, ZFS does not allow mounting on top of a nonempty directory. For example:
# zfs mount tank/home/lori cannot mount 'tank/home/lori': filesystem already mounted
Legacy mount points must be managed through legacy tools. An attempt to use ZFS tools results in an error. For example:
# zfs mount tank/home/bill cannot mount 'tank/home/bill': legacy mountpoint use mount(8) to mount this filesystem # mount -F zfs tank/home/billm
When a file system is mounted, it uses a set of mount options based on the property values associated with the file system. The correlation between properties and mount options is as follows:
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The mount option nosuid is an alias for nodevices,nosetuid.
You can use the NFSv4 mirror mount features to help you better manage NFS-mounted ZFS home directories.
When file systems are created on the NFS server, the NFS client can automatically discover these newly created file systems within their existing mount of a parent file system.
For example, if the server neo already shares the tank file system and client zee has it mounted, /tank/baz is automatically visible on the client after it is created on the server.
zee# mount neo:/tank /mnt zee# ls /mnt baa bar neo# zfs create tank/baz zee% ls /mnt baa bar baz zee% ls /mnt/baz file1 file2
If any of the mount options described in the preceding section are set explicitly by using the–o option with the zfs mount command, the associated property value is temporarily overridden. These property values are reported as temporary by the zfs get command and revert back to their original values when the file system is unmounted. If a property value is changed while the file system is mounted, the change takes effect immediately, overriding any temporary setting.
In the following example, the read-only mount option is temporarily set on the tank/home/neil file system. The file system is assumed to be unmounted.
# zfs mount -o ro users/home/neil
To temporarily change a property value on a file system that is currently mounted, you must use the special remount option. In the following example, the atime property is temporarily changed to off for a file system that is currently mounted:
# zfs mount -o remount,noatime users/home/neil NAME PROPERTY VALUE SOURCE users/home/neil atime off temporary # zfs get atime users/home/perrin
For more information about the zfs mount command, see the zfs(1M) man page.
You can unmount ZFS file systems by using the zfs unmount subcommand. The unmount command can take either the mount point or the file system name as an argument.
In the following example, a file system is unmounted by its file system name:
# zfs unmount users/home/mark
In the following example, the file system is unmounted by its mount point:
# zfs unmount /users/home/mark
The unmount command fails if the file system is busy. To forcibly unmount a file system, you can use the –f option. Be cautious when forcibly unmounting a file system if its contents are actively being used. Unpredictable application behavior can result.
# zfs unmount tank/home/eric cannot unmount '/tank/home/eric': Device busy # zfs unmount -f tank/home/eric
To provide for backward compatibility, the legacy umount command can be used to unmount ZFS file systems. For example:
# umount /tank/home/bob
For more information about the zfs umount command, see the zfs(1M) man page.