Sharing and Unsharing ZFS File Systems

Similar to mount points, ZFS can automatically share file systems by using the sharenfs property. Using this method, you do not have to modify the /etc/dfs/dfstab file when a new file system is added. The sharenfs property is a comma-separated list of options to pass to the share command. The special value on is an alias for the default share options, which are read/write permissions for anyone. The special value off indicates that the file system is not managed by ZFS and can be shared through traditional means, such as the /etc/dfs/dfstab file. All file systems whose sharenfs property is not off are shared during boot.

Controlling Share Semantics

By default, all file systems are unshared. To share a new file system, use zfs set syntax similar to the following:

# zfs set sharenfs=on tank/home/eschrock

The property is inherited, and file systems are automatically shared on creation if their inherited property is not off. For example:

# zfs set sharenfs=on tank/home
# zfs create tank/home/bricker
# zfs create tank/home/tabriz
# zfs set sharenfs=ro tank/home/tabriz

Both tank/home/bricker and tank/home/tabriz are initially shared writable because they inherit the sharenfs property from tank/home. Once the property is set to ro (readonly), tank/home/tabriz is shared read-only regardless of the sharenfs property that is set for tank/home.

Unsharing ZFS File Systems

While most file systems are automatically shared and unshared during boot, creation, and destruction, file systems sometimes need to be explicitly unshared. To do so, use the zfs unshare command. For example:

# zfs unshare tank/home/tabriz

This command unshares the tank/home/tabriz file system. To unshare all ZFS file systems on the system, you need to use the -a option.

# zfs unshare -a

Sharing ZFS File Systems

Most of the time the automatic behavior of ZFS, sharing on boot and creation, is sufficient for normal operation. If, for some reason, you unshare a file system, you can share it again by using the zfs share command. For example:

# zfs share tank/home/tabriz

You can also share all ZFS file systems on the system by using the -a option.

# zfs share -a

Legacy Share Behavior

If the sharenfs property is off, then ZFS does not attempt to share or unshare the file system at any time. This setting enables you to administer through traditional means such as the /etc/dfs/dfstab file.

Unlike the traditional mount command, the traditional share and unshare commands can still function on ZFS file systems. As a result, you can manually share a file system with options that are different from the settings of the sharenfs property. This administrative model is discouraged. Choose to either manage NFS shares completely through ZFS or completely through the /etc/dfs/dfstab file. The ZFS administrative model is designed to be simpler and less work than the traditional model. However, in some cases, you might still want to control file system sharing behavior through the familiar model.