Optimizing subdirectory mounting
Both direct and indirect maps contain a ``location'' field
where the filesystem to be mounted is specified.
The syntax of this field is:
server:pathname[:subdirectory]
We recommend that a subdirectory entry be provided in the ``location'' field when different map entries refer to the same mounted filesystem from the same server. This allows automount to work more efficiently. The following example shows a common use of subdirectories that optimizes the work of automount.
This indirect map shows a common way in which automount can be configured to distribute home directories from NFS servers to clients. Such a map may be called auto.home.
moscow moscow:/home/moscow prague prague:/home/prague zurich zurich:/home/zurichGiven this indirect map, every time a user wants to access a home directory in, for example, /home/moscow, all the directories under it are mounted. Another way to organize an auto.home map is by user name:
john moscow:/home/moscow/john mary moscow:/home/moscow/mary joe moscow:/home/moscow/joeThe above example assumes that home directories on the NFS client are of the form /home/user rather than /home/server/user. If a user now enters:
ls ~john ~\maryautomount performs the equivalent of:
mkdir /tmp_mnt/home/john mount -f NFS moscow:/home/moscow/john /tmp_mnt/home/john ln -s /tmp_mnt/home/john /home/johnIt is possible to optimize the work done by automount by modifying the entries in the auto.home map to use the optional ``subdirectory'' field of the ``location'' field of the indirect map. The new auto.home map looks like:mkdir /tmp_mnt/home/mary mount -f NFS moscow:/home/moscow/mary /tmp_mnt/home/mary ln -s /tmp_mnt/home/mary /home/mary
john moscow:/home/moscow:john mary moscow:/home/moscow:mary joe moscow:/home/moscow:joeHere ``john,'' ``mary,'' and ``joe'' are entries in the ``subdirectory'' field. Now when a user refers to john's home directory, automount mounts moscow:/home/moscow and links /tmp_mnt/home/moscow/john and /home/john.
If the user then requests access to mary's home directory, automount sees that moscow:/home/moscow is already mounted, and simply links /tmp_mnt/home/moscow/mary and /home/mary. Therefore, automount now performs only the equivalent of:
mkdir /tmp_mnt/home/john mount -f NFS moscow:/home/moscow /tmp_mnt/home ln -s /tmp_mnt/home/john /home/john ln -s /tmp_mnt/home/mary /home/mary
See also: