System Administration Guide: Devices and File Systems

Creating and Mounting a Loopback File System (LOFS)

An LOFS file system is a virtual file system that provides an alternate path to an existing file system. When other file systems are mounted onto an LOFS file system, the original file system does not change.

For more information, see the lofs(7FS).

Note –

Be careful when creating LOFS file systems. Because LOFS file systems are virtual file systems, the potential for confusing both users and applications is enormous.

ProcedureHow to Create and Mount an LOFS File System

  1. Become superuser or assume an equivalent role.

  2. Create the directory you want to mount as an LOFS file system, if necessary.

    # mkdir loopback-directory
  3. Grant the appropriate permissions and ownership on the newly created directory.

  4. Create the mount point where you want to mount the LOFS file system, if necessary.

    # mkdir /mount-point
  5. Mount the LOFS file system.

    # mount -F lofs loopback-directory /mount-point

    Specifies the file system to be mounted on the loopback mount point.


    Specifies the directory on which to mount the LOFS file system.

  6. Verify that the LOFS file system has been mounted.

    # mount -v

Example 18–4 Creating and Mounting an LOFS File System

The following example shows how to create, mount, and test new software in the /new/dist directory as a loopback file system without actually having to install it.

# mkdir /tmp/newroot
# mount -F lofs /new/dist /tmp/newroot
# chroot /tmp/newroot newcommand

Example 18–5 Mounting an LOFS File System at Boot Time

You can set up the system to automatically mount an LOFS file system at boot time by adding an entry to the end of the /etc/vfstab file. The following example shows an entry in the /etc/vfstab file that mounts an LOFS file system for the root (/) file system on /tmp/newroot.

/ - /tmp/newroot  lofs   -  yes  -

Ensure that the loopback entries are the last entries in the /etc/vfstab file. Otherwise, if the /etc/vfstab entry for a loopback file system precedes the file systems to be included in it, the loopback file system cannot be mounted.

See Also

For more information on the /etc/vfstab file, see Field Descriptions for the /etc/vfstab File.