Types of NFS mounts

There are three types of NFS mounts: predefined, explicit, and automatic.

Predefined mounts are specified in the /etc/filesystems file. Each stanza (or entry) in this file defines the characteristics of a mount. Data such as the host name, remote path, local path, and any mount options are listed in this stanza. Predefined mounts are used when certain mounts are always required for proper operation of a client.

Explicit mounts serve the needs of the root user. Explicit mounts are usually done for short periods of time when there is a requirement for occasional unplanned mounts. Explicit mounts can also be used if a mount is required for special tasks and that mount is not generally available on the NFS client. These mounts are usually fully qualified on the command line by using the mount command with all needed information. Explicit mounts do not require updating the /etc/filesystems file. File systems mounted explicitly remain mounted unless explicitly unmounted with the umount command or until the system is restarted.

Automatic mounts are controlled by the automount command, which causes the AutoFS kernel extension to monitor specified directories for activity. If a program or user attempts to access a directory that is not currently mounted, then AutoFS intercepts the request, arranges for the mount of the file system, then services the request.