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This part describes the Solaris 2.x automounter services in two chapters.
Chapter 7 describes automount terminology and the components of automounting, explains how the automounter works, recommmends automounting policies, and tells you how to plan your automounter services. Chapter 8 describes how to set up and administer automounter maps.
Refer to the chapters in this part if you need to set up a new automount service or modify an existing one.
THE AUTOMOUNTER WORKS WITH THE NFS (NETWORK FILE SYSTEM) TO AUTMATICALLY mount and unmount directories from other systems on the network as they are needed. The automounter supplements the virtual file system table (/etc/vfstab) and manual mount and unmount activities with an automatic, on-demand facility. When the user types a command that accesses a remote file or directory, the automounter consults a series of maps—described in detail later in this chapter—to determine which directories to mount, which system to mount them from, which mount parameters to use, and where to mount them on the user’s local system. The directory remains mounted as long as it is in use. When the user exits from the file or the directory, the resource is automatically unmounted if it has not been accessed for 5 minutes.
Although you could administer the automounter by editing local automount maps in the /etc directory, SunSoft recommends that you use the NIS+ naming service with the automounter. Using NIS+ creates a consistent global namespace for your users and a centralized control model for your administrators, and it provides a consistent automounter configuration throughout the domain. The instructions in this chapter and in Chapter 8, "Setting Up the Automounter," are for the recommended configuration, which is using the automounter with NIS+. (All About Administering NIS+, by Rick Ramsey, offers complete instructions for setting up and administering NIS+; see the bibliography at the end of this book for the complete reference.)
SunOS 5.x system software uses the SunOS 4.x automount program with some minor modifications. If you are familiar with SunOS 4.x automount services, you can easily set up and administer the automounter for SunOS 5.x systems. You will find that it is easy to administer automounting on a network in which some systems run SunOS 4.x and others run SunOS 5.x system software.
This chapter describes some automount terminology, the automount maps and mount points, and how automounting works. It also provides some example maps and suggests policies you can use to implement automounting in your network environment. (How to create and edit automount maps is discussed in the next chapter.)
NFS, which is the SunOS 5.x distributed network file system, is the industry’s most widely available file-sharing system, which has been adopted and shipped by more than 300 vendors. The terms in this discussion are commonly used to describe how resources are shared using NFS and how these terms relate to the automounter.
The terms server and client are used to describe the roles that systems perform when they interact to share resources. These terms are part of general distributed computing terminology and are not specific to either NFS or the automounter.
You do not need to set up server file systems in a special way for access by the automounter. As long as the file systems are shared for NFS access, the automounter software can mount and unmount them.
Mount points are directories on a client system that are used as places to attach (or mount) other file systems. When you mount or automount a file system on a mount point, any files or directories that are stored locally in the mount point directory are hidden and inaccessible as long as the file system is mounted. These files are not permanently affected by the mounting process, and they become available again when the file system is unmounted. However, mount directories are usually empty so that existing files are not obscured.
Each system has a virtual file system table (/etc/vfstab) that specifies which file systems are mounted by default at system boot. Local ufs (UNIX file system) and NFS that are mounted automatically when a system boots are specified in this file. The /etc/vfstab file has additional entries for file systems, such as swap and proc, that are used by the system. In addition, the /etc/vfstab file may have entries for pcfs (personal computer file system) and cdrom file systems.
The automounter does not use the /etc/vfstab file to specify which file systems to mount and unmount. It uses maps instead because they are more flexible and they enable a consistent network-wide view of all filenames.
You can mount some file systems using the /etc/vfstab file and other files, using the automounter without any conflict. In fact, some file systems—such as local file systems and file systems exported with the share command from a server—must not be automounted.
CAUTION! Do not create entries in the /etc/vfstab file for file systems that will be automounted. Conversely, do not put file systems that are included in the /etc/vfstab file into any of the automount direct maps. These redundant entries can seriously degrade system performance and generate much unnecessary network traffic.
User file systems are mounted when the system boots using entries in the /etc/vfstab file. When file systems are not automounted, users employ the mount and umount commands—which require superuser privileges—if they need to mount any additional file systems or unmount a mounted file system. The mount command is used to mount a file system. The umount command is used to unmount a file system. When file systems are automounted, users do not need to use the mount and umount commands.
For a description of the types of file systems and for information on how to share, mount, and unmount files, refer to Solaris System Administrator’s Guide, by Janice Winsor. (See the bibliography at the end of this book.)
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