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. This field contains no uppercase characters, and must not be more than eight characters in length.

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.) A & 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 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

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:

passwd: compat

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

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