Network File System (NFS) or distribution?

Probably the first thing you are interested in doing with a network (after you've had your fill of the world wide web) is to make your files available to some or all hosts on the network, no matter where in your corporate empire (or university dungeon) you might be sitting. In other words, if you have a disk which is physically connected to host A, you would like to make the contents of that disk available to hosts B, C, D... etc. NFS (the network filesystem) does this for you. The process works by `filesystems'.

A filesystem is one partition of a disk drive -- or one unit of disk space which can be accessed by a single `logical device' `/dev/something'. To make a filesystem available to other hosts you have to do three things.

• On the host the disk is physically connected to you must export the filesystem by adding something to the file `/etc/exports'. This tells NFS who is allowed to access the disk and who isn't.
• On the host which is to access the filesystem you must create a mount point. This is a name in the directory tree at which you want to add the files to your local filesystem.
• On the host which is to access the files you must mount the filesystem onto the mount point. The mount operation is the jargon for telling the system to access the device on which the data are stored. Mounting is analogous to opening a file: files are opened, filesystems are mounted.

Only after all three of these have been done will a filesystem become available across the network. Cfengine will help you with the last two in a very transparent way. You could also use the text-editing facility in cfengine to edit the exports file, but there are other ways update the exports file using netgroups which we shall not go into here. If you are in doubt, look up the manual page on exports.

Some sites prefer to minimize the use of NFS filesystems, to avoid one machine being dependent on another. They prefer to make a local copy of the files on a remote machine instead. Traditionally programs like rdist have been used for this purpose. You may also use cfengine to copy files in this way, See section Remote file distribution.

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