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.

uid is the user’s unique numerical ID for the system.

gid is the unique numerical ID of the group that 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/passwd
/etc/shadow
/etc/nsswitch.conf

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