Chapter 34. HP-UX Automounter | HP Certified: HP-UX System Administration

Chapter Syllabus

34.1 Automounter Maps

34.2 Configuring Automounter

Automounter may be considered an additional service to an NFS client. An NFS client usually mounts file systems from the NFS server at boot time and keeps these file systems mounted while the system is up. The file systems are unmounted at system shutdown time. The Automounter, on the other hand, mounts remote file systems only when needed. If a mounted file system is not accessed for a specified period of time, it is automatically unmounted. The automount daemon keeps this process totally transparent from the user . Automounter is a client-side service and is installed with the NFS client. All file systems and directories should be exported by NFS in the normal way as used with the NFS client.

Automounter uses map files to find mount points and server-exported file systems and directories. The maps are stored in plain text files. By default, the automount daemon gets its information from the master map file, /etc/auto_master , that contains a list of other map files and their locations.

All map files contain information about NFS servers, directories exported by NFS servers, and local mount points along with mount options. In a direct map, mount points for all remote file systems and directories are specified in absolute form. In an indirect map, a common mount point for many directories is specified. An example of an indirect map is user home directories. The reference mount point for these directories may be /home , while all directories are mounted relative to /home such that each mounted directory is visible inside the /home directory. The special maps are used are used for predefined purposes.

The Automounter system is very useful for load balancing when the same directories can be mounted from multiple NFS servers. An example of this is the directories containing manual pages. All NFS servers have the same copy of manual pages, and it makes no difference from which NFS server the directory is mounted. Multiple NFS servers can be listed against one local mount point inside Automounter maps. The Automounter system finds the nearest NFS server and mounts directories from this server. The system uses the ping command to send some data to all servers and calculates the distance of a particular data packet using the time taken by this packet to return. In addition to the physical distance of an NFS server from a client, this method also works well to distinguish high traffic network paths and heavily loaded servers. The same method also provides fault tolerance such that if one NFS server is not available at a particular time, the client can mount directories from another server.

This chapter starts with an introduction to Automounter maps. Here, master, direct, indirect, and special maps are explained. The effect of changing a map on the automount daemon is also presented. The next section is dedicated to the configuration of Automounter. After completing this chapter, you will be able to configure Automounter on an NFS client.

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