Five network authorization systems in use today are:

These systems all take the information that is usually stored in each workstation’s /etc/passwd file and store it in one or more network servers. Some systems use the network-based account to supersede the accounts on the local system; others augment the local accounts with network-based accounts.

Some of these systems provide for multiple servers or backup caching, should the primary server be unavailable. Others do not, and instead create a single point of failure for the entire network.

At some sites, administrators prefer not to use network database management systems. Instead, each computer might have its own accounts. Alternatively, one computer might be regarded as the “master computer,” and that computer’s /etc/passwd and /etc/shadow files are then distributed to other computers using scp, rdist, or a similar system. There are several reasons that an administrator might make such a decision.

The drawback to this approach is that it often requires the administrator to intervene to change a user password or shell entry. In most cases, the energy spent developing and fielding custom solutions would be better spent mastering systems that are already in existence and, in many cases, preinstalled on most Unix systems.

If you are using one of these systems and wish to retrieve the contents of the password database, you cannot simply cat the /etc/passwd file. Instead, you must use a command that is specific to your system to view the account database.

Sun’s NIS service supplements the information stored in the workstations’ own files. If you are using NIS and you wish to get a list of every user account, you would use the following command:

% cat /etc/passwd;ypcat passwd

% niscat -o passwd.bigco

% nidump passwd .