Provided by: openafs-client_1.8.13.2-1ubuntu1_amd64 
NAME
fs_mkmount - Creates a mount point for a volume
SYNOPSIS
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]
DESCRIPTION
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.
• When the Cache Manager crosses a regular mount point, it obeys all three of the mount point traversal
rules previously described. To create a regular mount point, include only the required -dir and -vol
arguments to the fs mkmount command.
• When the Cache Manager crosses a read/write mount point, it attempts to access only the volume
version named in the mount point. If the volume name is the base (read/write) form, without a
".readonly" or ".backup" extension, the Cache Manager accesses the read/write version of the volume,
even if it is replicated. In other words, the Cache Manager disregards the second mount point
traversal rule when crossing a read/write mount point: it switches to the read/write path through the
filespace.
To create a read/write mount point, include the -rw flag on the fs mkmount command. It is
conventional to create only one read/write mount point in a cell's filespace, using it to mount the
cell's "root.cell" volume just below the AFS filespace root (by convention, /afs/.cellname). See the
OpenAFS Quick Start Guide for instructions and the chapter about volume management in the OpenAFS
Administration Guide for further discussion.
Creating a read/write mount point for a read-only or backup volume is acceptable, but unnecessary.
The first rule of mount point traversal already specifies that the Cache Manager accesses them if the
volume name in a regular mount point has a ".readonly" or ".backup" extension.
• When the Cache Manager crosses a cellular mount point, it accesses the indicated volume in the
specified cell, which is normally a foreign cell. (If the mount point does not name a cell along with
the volume, the Cache Manager accesses the volume in the cell where the mount point resides.) The
Cache Manager disregards the third mount point traversal rule when crossing a regular cellular mount
point: it accesses a read-only version of the volume if it is replicated, even if the volume that
houses the mount point is read/write. Switching to the read-only path in this way is designed to
avoid imposing undue load on the file server machines in foreign cells.
To create a regular cellular mount point, include the -cell argument on the fs mkmount command. It is
conventional to create cellular mount points only at the second level in a cell's filespace, using
them to mount foreign cells' root.cell volumes just below the AFS filespace root (by convention, at
/afs/foreign_cellname). The mount point enables local users to access the foreign cell's filespace,
assuming they have the necessary permissions on the ACL of the volume's root directory and that there
is an entry for the foreign cell in each local client machine's /etc/openafs/CellServDB file. In the
output of the fs lsmount command, the cell name and a colon (":") appear between the initial number
sign and the volume name in a regular cellular mount point name.
OPTIONS
-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/.example.com). 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 /etc/openafs/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.
-rw Creates a read/write mount point. Omit this flag to create a regular mount point.
-fast
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.
-help
Prints the online help for this command. All other valid options are ignored.
EXAMPLES
The following command creates a regular mount point, mounting the volume "user.smith" at
/afs/example.com/usr/smith:
% cd /afs/example.com/usr
% fs mkmount -dir smith -vol user.smith
The following commands create a read/write mount point and a regular mount point for the Example
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/example.com -vol root.cell
% fs mkmount -dir /afs/.example.com -vol root.cell -rw
The following command mounts the Example Organization cell's "root.cell" volume in the Example
Corporation cell's file tree, creating a regular cellular mount point called /afs/example.org. When a
Example Corporation Cache Manager encounters this mount point, it crosses into the Example Organization
cell on a read-only path.
% fs mkmount -dir /afs/example.org -vol root.cell -c example.org
PRIVILEGE REQUIRED
The issuer must have the "i" (insert) and "a" (administer) permissions on the ACL of the directory that
is to house the mount point.
SEE ALSO
CellServDB(5), fs_lsmount(1), fs_rmmount(1)
COPYRIGHT
IBM Corporation 2000. <http://www.ibm.com/> 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.
OpenAFS 2025-03-21 FS_MKMOUNT(1)