fs_mkmount - Creates a mount point for a volume


fs mkmount -dir <directory> -vol <volume name> [-cell <cell name>] [-rw] [-fast] [-help]

fs mk -d <directory> -v <volume name> [-c <cell name>] [-r] [-f] [-h]


The fs mkmount command creates a mount point for the volume named by the -vol argument at the location in the AFS file space specified by the -dir argument. The mount point looks like a standard directory element, and serves as the volume's root directory, but is actually a special file system object that refers to an AFS volume. When the Cache Manager first encounters a given mount point during pathname traversal, it contacts the VL Server to learn which file server machines house the indicated volume, then fetches a copy of the volume's root directory from the appropriate file server machine.

It is possible, although not recommended, to create more than one mount point to a volume. The Cache Manager can become confused if a volume is mounted in two places along the same path through the filespace.

The Cache Manager observes three basic rules as it traverses the AFS filespace and encounters mount points:

Rule 1: Access Backup and Read-only Volumes When Specified

When the Cache Manager encounters a mount point that specifies a volume with either a .readonly or a .backup extension, it accesses that type of volume only. If a mount point does not have either a .backup or .readonly extension, the Cache Manager uses Rules 2 and 3.

For example, the Cache Manager never accesses the read/write version of a volume if the mount point names the backup version. If the specified version is inaccessible, the Cache Manager reports an error.

Rule 2: Follow the Read-only Path When Possible

If a mount point resides in a read-only volume and the volume that it references is replicated, the Cache Manager attempts to access a read-only copy of the volume; if the referenced volume is not replicated, the Cache Manager accesses the read/write copy. The Cache Manager is thus said to prefer a read-only path through the filespace, accessing read-only volumes when they are available.

The Cache Manager starts on the read-only path in the first place because it always accesses a read-only copy of the root.afs volume if it exists; the volume is mounted at the root of a cell's AFS filespace (named /afs by convention). That is, if the root.afs volume is replicated, the Cache Manager attempts to access a read-only copy of it rather than the read/write copy. This rule then keeps the Cache Manager on a read-only path as long as each successive volume is replicated. The implication is that both the root.afs and root.cell volumes must be replicated for the Cache Manager to access replicated volumes mounted below them in the AFS filespace. The volumes are conventionally mounted at the /afs and /afs/cellname directories, respectively.

Rule 3: Once on a Read/write Path, Stay There

If a mount point resides in a read/write volume and the volume name does not have a .readonly or a .backup extension, the Cache Manager attempts to access only the read/write version of the volume. The access attempt fails with an error if the read/write version is inaccessible, even if a read-only version is accessible. In this situation the Cache Manager is said to be on a read/write path and cannot switch back to the read-only path unless mount point explicitly names a volume with a .readonly extension. (Cellular mount points are an important exception to this rule, as explained in the following discussion.

There are three types of mount points, each appropriate for a different purpose because of the manner in which the Cache Manager interprets them.


-dir <directory>+

Names the directory to create as a mount point. The directory must not already exist. Relative pathnames are interpreted with respect to the current working directory.

Specify the read/write path to the directory, to avoid the failure that results from attempting to create a new mount point in a read-only volume. By convention, the read/write path is indicated by placing a period before the cell name at the pathname's second level (for example, /afs/ For further discussion of the concept of read/write and read-only paths through the filespace, see DESCRIPTION.

-vol <volume name>

Specifies the name or volume ID number of the volume to mount. If appropriate, add the .readonly or .backup extension to the name, or specify the appropriate volume ID number.

-cell <cell name>

Names the cell in which the volume resides (creates a cellular mount point). Provide the fully qualified domain name, or a shortened form that disambiguates it from the other cells listed in the local /usr/vice/etc/CellServDB file.

If this argument is omitted, no cell indicator appears in the mount point. When the Cache Manager interprets it, it assumes that the volume named in the mount point resides in the same cell as the volume that houses the mount point.


Creates a read/write mount point. Omit this flag to create a regular mount point.


Prevents the Volume Location (VL) Server from checking that the volume has a VLDB entry and printing a warning message if it does not. Whether or not this flag is included, the File Server creates the mount point even when the volume has no VLDB entry.


Prints the online help for this command. All other valid options are ignored.


The following command creates a regular mount point, mounting the volume user.smith at /afs/

   % cd /afs/
   % fs mkmount -dir smith -vol user.smith

The following commands create a read/write mount point and a regular mount point for the ABC Corporation cell's root.cell volume in that cell's file tree. The second command follows the convention of putting a period at the beginning of the read/write mount point's name.

   % fs mkmount -dir /afs/ -vol root.cell
   % fs mkmount -dir /afs/ -vol root.cell -rw

The following command mounts the State University cell's root.cell volume in the ABC Corporation cell's file tree, creating a regular cellular mount point called /afs/ When a ABC Corporation Cache Manager encounters this mount point, it crosses into the State University cell on a read-only path.

   % fs mkmount -dir /afs/ -vol root.cell -c


The issuer must have the i (insert) and a (administer) permissions on the ACL of the directory that is to house the mount point.


CellServDB(5), fs_lsmount(1), fs_rmmount(1)


IBM Corporation 2000. <> All Rights Reserved.

This documentation is covered by the IBM Public License Version 1.0. It was converted from HTML to POD by software written by Chas Williams and Russ Allbery, based on work by Alf Wachsmann and Elizabeth Cassell.