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Solaris NFS Environment
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- This chapter provides an overview of the Solaris network file system (NFS) environment.
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- The NFS system allows you to share files and directories among many computers on a network. For example, applications running simultaneously on several computers can read from and write to a single file system. To participating users, the file system appears to be located on their local systems. The possible uses for shared file systems are endless.
- The terms client and server are used to describe the roles that a computer plays when sharing file systems. If a central file system resides on a computer's disk, and that computer makes the file system available to other computers on the network, that computer acts as a server. The computers that are accessing that central file system are said to be clients. Solaris NFS software enables any given computer to access any other computer's file systems and, at the same time, provide access to its own file systems. A computer may play the role of client and server or both at any given time on a network.
NFS System
- The NFS system is a SunSoft distributed computing file system that can be used to link computers that are running different operating systems. For example, computers running DOS can share files with computers running UNIX.
- The NFS system makes the actual physical location of the file system irrelevant to the user. You can use the NFS system to enable users to see all the relevant files, regardless of location. Instead of placing copies of commonly used files on every system, the NFS software allows you to place one copy on one computer's disk and have all other systems access it across the network. Under NFS operation, remote file systems are indistinguishable from local ones.
- A computer becomes an NFS server if it has file systems to export over the network. A server keeps a list of currently exported file systems and their access restrictions (read/write, read-only, and so on).
Autofs
- File systems shared through NFS software can be mounted using automatic mounting. Autofs, a client-side service, is a file system that provides advanced automatic mounting. The automount program runs in the background mounting and unmounting remote directories on an as-needed basis.
- Whenever a user on a client computer running autofs tries to access a remote file or directory, autofs mounts the file system to which that file or directory belongs. This remote file system remains mounted for as long as it is needed. If the remote file system is not accessed for a certain period of time, it is automatically unmounted.
- No mounting is done at boot time, and the user no longer has to know the superuser password to mount a directory; users need not use the mount and umount commands. Autofs mounts and unmounts file systems as required without any intervention on the part of the user.
- Mounting some file hierarchies with automount does not exclude the possibility of mounting others with mount. A diskless computer must mount / (root), /usr, and /usr/kvm through the mount and the /etc/vfstab file. Do not use autofs to mount /usr/share. Automountd depends on some files in that directory.
Autofs Features
- Autofs works with file systems specified in NIS maps or NIS+ tables. These maps or tables can be maintained as NIS, NIS+, or local files.
- Autofs maps or tables can specify several remote locations for a particular file. This way, if one of the servers is down, autofs can try to mount from another computer. To specify which servers are preferred for each file system in the maps, you can assign each server a weighting factor.
- You can invoke autofs from a shell command line, or it will start automatically when the computer enters run level 2.
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