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Using the NFS Client

Logging on to the NFS Network

NFS servers use a UNIX, or POSIX, file-permission system. This system gives each user a user identification number (UID), a group identification number (GID), and possibly several additional supplementary GIDs. Each file is assigned ownership by UID and by GID. Permissions for the file are set based on whether the user who wants access is the owner (has the same UID as the file), is in the file's group (has a GID that matches the GID of the file), or is some other user. For each of these three categories (owner, group, and other) read, write, and execute permissions can be assigned.

To access files that use NFS, your session on OS/390 or CMS must acquire UID and GID numbers that correspond to some user on the NFS server network. You acquire these numbers by contacting a login server on the NFS network to ask permission to access files according to a username that is known to that server. In many cases, contact with the NFS login server can be automatic the first time that you access an NFS file. In other cases, you must issue the NFSLOGIN command to effect the login.

The function of the login server is to check your identification and grant you access to the network. Once you are logged on, the login server functions as an NFS server and provides access to the files that are located on the machine on which it resides. At this point you may also use the network to access files that are controlled by other NFS servers on other machines.

If you have a RACF-compatible security system running on your mainframe and your site administration has given you access to your NFS login server username, then the security system suffices and no password is required. Note that the login server username is not necessarily the same as your OS/390 or CMS userid. If you do not have a security system, then you will need to type your password during the login process.

In summary, the login process can involve three pieces of information:

The requirement for a password depends on whether a mainframe security system can provide authentication for login server usernames. If the NFS client software can determine the other two pieces of information, either by default or by environment variables, then automatic login is possible. Otherwise, the NFSLOGIN command must be used.

For example, if your NFS network is composed of UNIX machines, your UNIX username is comkzz , and your login server is a UNIX machine called byrd.unx , then the CSL NFS client software must contact byrd.unx and provide comkzz as the user name. If your OS/390 username is also COMKZZ (the same except that it is uppercase), the mainframe security administrator has authorized you to use the comkzz username for NFS, and if byrd.unx has been configured as the default login server at your site, then the NFS client library will log you in automatically the first time you try to use NFS.

If, on the other hand, your site does not have RACF, a password is required. In this case, you need to issue the NFSLOGIN command to type your password. See NFSLOGIN for details.

After the login processing has succeeded, your session receives a UID and one or more GIDs. These control your subsequent accesses to NFS files.


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