Name

passwd − password file description with the Yellow Pages service implemented

Description

The passwd file stores initial login information, including passwords for each user in the system. Regardless of whether or not the system has the Yellow Pages service implemented, the passwd file contains the following information:

Name (login name, contains no uppercase)

Encrypted password

Numerical user ID

Numerical group ID

User’s real name, office, extension, home phone. 

Initial working directory

Program to use as Shell

The name can contain an ampersand (&), meaning insert the login name.  This information is set by the chfn() command and used by the finger() command.

This is an ASCII file.  Each field within each user’s entry is separated from the next by a colon.  Each user is separated from the next by a new line.  If the password field is null, no password is demanded; if the shell field is null, the system defaults to the /bin/sh shell.

This file resides in the /etc directory. Because of the encrypted passwords, it can and does have general read permission and can be used, for example, to map numerical user IDs to names.

Appropriate precautions must be taken to lock the /etc/passwd file against simultaneous changes if it is to be edited with a text editor. The vipw command does the necessary locking.

In a Yellow Pages environment, the passwd file can also have a line beginning with a plus (+), which means to incorporate entries from the Yellow Pages data base. There are three styles of + entries: by itself, + means to insert the entire contents of the Yellow Pages password file at that point; +name means to insert the entry (if any) for name from the Yellow Pages at that point; +@name means to insert the entries for all members of the network group name at that point.  If a + entry has a nonnull password, directory, gecos, or shell field, it will override what is contained in the Yellow Pages.  The numerical user ID and group ID fields cannot be overridden. 

Examples

Here is a sample /etc/passwd file:

root:q.mJzTnu8icF.:0:10:Privileged Account:/:/bin/csh
jcj:6k/7KCFRPNVXg:508:10:JC Javert:/usr2/jcj:/bin/csh
+john:
+@documentation:no-login:
+:::Guest

In this example, there are specific entries for users root and jcj, in case the Yellow Pages are temporarily out of service.  Alternatively, a user may need specific login information on a given system that differs from the information contained in the Yellow Pages map for that user.  The user, john, will have his password entry in the Yellow Pages incorporated without change.  Anyone in the netgroup documentation will have their password field disabled, and anyone else will be able to log in with their usual password, shell, and home directory, but with a gecos field of Guest. 

Files

/etc/passwd

See Also

chfn(1), finger(1), login(1), passwd(1), crypt(3), getpwent(3), group(5), adduser(8), vipw(8)