If you have configured your SP to include both automounter and user management support, the SP will create and maintain an automount map file for users' home directories. When you add a new SP user to your system, a map entry will be added to /etc/auto/maps/auto.u associating the user's /u home directory with the actual physical directory located either on the current machine or on a remote file server that can be accessed through a network connection using NFS. This map entry will be changed or removed when SP User Management functions are used to change or remove the user from the system.
If you have existing users that do not have entries in the auto.u map file, you can use the mkamdent command to add home directory entries for them. The mkamdent command allows you to specify a list of users to add to the auto.u map. The command builds a stanza for each user in the list using the SP site environment values for homedir_server and homedir_path as the defaults (these can be set using SMIT panels or the spsitenv command). homedir_server is the default file server and homedir_path is the default base path for the home directory (not including the individual user's subdirectory). You can override these defaults with the -s flag. See PSSP: Command and Technical Reference for more information on the mkamdent and spsitenv commands.
You must make sure that the /u directory is not a symbolic link to some other directory. This will prevent the automount daemon from starting successfully. /u must exist as a local directory on each processor.
If you are not using SP User Management services, but would still like to have the automount daemon control access to directories in the /u file system, you can create and maintain your own auto.u map file. See Using automount for other file systems for details on how to add the map to the SP automounter support.
It may become necessary to change the user home directory information stored in the automounter map file. If, for example, the home directory is moved to a new server machine or to a different directory, the existing entry in the automounter map file will need to be updated with the new information. IBM suggests changing this information by using the spchuser command or the equivalent SMIT panels.
After updating the map file, you may need to wait up to 5 minutes with no access attempts to the user's home directory through the /u file system. This allows the automounter to time out any previous access attempts and unmount any existing mounts that may be referencing the old information. Do not attempt to force the unmount by manually issuing the umount command as that will put the automounter in an inconsistent state. You would then need to stop and restart the automount daemon to recover access to that user's home directory.