passwd(4) (man pages section 4: File Formats)

man pages section 4: File Formats

passwd(4)

NAME

passwd- password file

SYNOPSIS

/etc/passwd

DESCRIPTION

/etc/passwd is a local source of information about users' accounts. The password file can be used in conjunction with other password sources, including the NIS maps passwd.byname and passwd.bygid and the NIS+ table passwd. Programs use the getpwnam(3C) routines to access this information.

Each passwd entry is a single line of the form:

username:password:uid:
gid:gcos-field:home-dir:
login-shell

where

username: is the user's login name. It is recommended that this field conform to the checks performed by pwck(1M).
password: is an empty field. The encrypted password for the user is in the corresponding entry in the /etc/shadow file. pwconv(1M) relies on a special value of 'x' in the password field of /etc/passwd. If this value of 'x' exists in the password field of /etc/passwd, this indicates that the password for the user is already in /etc/shadow and should not be modified.
uid: is the user's unique numerical ID for the system.
gid: is the unique numerical ID of the group that the user belongs to.
gcos-field: is the user's real name, along with information to pass along in a mail-message heading. (It is called the gcos-field for historical reasons.) An ``&'' (ampersand) in this field stands for the login name (in cases where the login name appears in a user's real name).
home-dir: is the pathname to the directory in which the user is initially positioned upon logging in.
login-shell: is the user's initial shell program. If this field is empty, the default shell is /usr/bin/sh.

The maximum value of the uid and gid fields is 2147483647. To maximize interoperability and compatibility, administrators are recommended to assign users a range of UIDs and GIDs below 60000 where possible.

The password file is an ASCII file. Because the encrypted passwords are always kept in the shadow file, /etc/passwd has general read permission on all systems and can be used by routines that map between numerical user IDs and user names.

Previous releases used a password entry beginning with a `+' (plus sign) or `-' (minus sign) to selectively incorporate entries from NIS maps for password. If still required, this is supported by specifying ``passwd : compat'' in nsswitch.conf(4). The "compat" source may not be supported in future releases. The preferred sources are, "files" followed by "nisplus". This has the effect of incorporating the entire contents of the NIS+ passwd table after the password file.

EXAMPLES

Example 1 A sample `passwd` file.

Here is a sample passwd file:

root:q.mJzTnu8icF.:0:10:God:/:/bin/csh
fred:6k/7KCFRPNVXg:508:10:& Fredericks:/usr2/fred:/bin/csh

and the sample password entry from nsswitch.conf:

passwd: files nisplus

In this example, there are specific entries for users root and fred to assure that they can login even when the system is running single-user. In addition, anyone in the NIS+ table passwd will be able to login with their usual password, shell and home directory.

If the password file is:

root:q.mJzTnu8icF.:0:10:God:/:/bin/csh
fred:6k/7KCFRPNVXg:508:10:& Fredericks:/usr2/fred:/bin/csh
+

and the password entry from nsswitch.conf is:

passwd: compat

then all the entries listed in the NIS passwd.byuid and passwd.byname maps will be effectively incorporated after the entries for root and fred.

FILES

/etc/nsswitch.conf
/etc/passwd
/etc/shadow