PASSWD(5) — FILE FORMATS

NAME

passwd − password file

SYNOPSIS

/etc/passwd

DESCRIPTION

The passwd file contains for each user the following information:

nameUser’s login name — contains no upper case characters and must not be greater than eight characters long.

passwordencrypted password

numerical user ID
This is the user’s ID in the system and it must be unique.

numerical group ID
This is the number of the group that the user belongs to.

user’s real name
In some versions of UNIX, this field also contains the user’s office, extension, home phone, and so on. For historical reasons this field is called the GCOS field.

initial working directory
The directory that the user is positioned in when they log in — this is known as the ‘home’ directory.

shellprogram to use as Shell when the user logs in.

The user’s real name field may contain ‘&’, meaning insert the login name.

The password file 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, /bin/sh is used.

The passwd file can also have line beginning with a plus (+), which means to incorporate entries from the yellow pages. There are three styles of + entries: all 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 non-null password, directory, gecos, or shell field, they will overide what is contained in the yellow pages. The numerical user ID and group ID fields cannot be overridden.

EXAMPLE

Here is a sample /etc/passwd file:

root:q.mJzTnu8icF.:0:10:God:/:/bin/csh
tut:6k/7KCFRPNVXg:508:10:Bill Tuthill:/usr2/tut:/bin/csh
+john:
+@documentation:no-login:
+:::Guest

In this example, there are specific entries for users root tut, in case the yellow pages are out of order. The user 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.

The password file resides in the /etc directory. Because of the encrypted passwords, it has general read permission and can be used, for example, to map numerical user ID’s 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; vipw(8) does the necessary locking.

FILES

/etc/passwd

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