passwd - password files
Passwd files are files consisting of newline separated records, one per user, containing
ten colon (``:'') separated fields. These fields are as follows:
name user's login name
password user's encrypted password
uid user's id
gid user's login group id
class user's general classification (unused)
change password change time
expire account expiration time
gecos general information about the user
home_dir user's home directory
shell user's login shell
The name field is the login used to access the computer account, and the uid field is the
number associated with it. They should both be unique across the system (and often across
a group of systems) since they control file access.
While it is possible to have multiple entries with identical login names and/or identical
user id's, it is usually a mistake to do so. Routines that manipulate these files will
often return only one of the multiple entries, and that one by random selection.
The login name must never begin with a hyphen (``-''); also, it is strongly suggested that
neither upper-case characters or dots (``.'') be part of the name, as this tends to con-
fuse mailers. No field may contain a colon (``:'') as this has been used historically to
separate the fields in the user database.
The password field is the encrypted form of the password. If the password field is empty,
no password will be required to gain access to the machine. This is almost invariably a
mistake. Because these files contain the encrypted user passwords, they should not be
readable by anyone without appropriate privileges.
The group field is the group that the user will be placed in upon login. Since this sys-
tem supports multiple groups (see groups(1)) this field currently has little special mean-
The class field is currently unused. In the near future it will be a key to a termcap(5)
style database of user attributes.
The change field is the number in seconds, GMT, from the epoch, until the password for the
account must be changed. This field may be left empty to turn off the password aging fea-
The expire field is the number in seconds, GMT, from the epoch, until the account expires.
This field may be left empty to turn off the account aging feature.
The gecos field normally contains comma (``,'') separated subfields as follows:
name user's full name
office user's office number
wphone user's work phone number
hphone user's home phone number
This information is used by the finger(1) program.
The user's home directory is the full UNIX path name where the user will be placed on
The shell field is the command interpreter the user prefers. If the shell field is empty,
the Bourne shell (/bin/sh) is assumed.
chpass(1), login(1), passwd(1), getpwent(3), mkpasswd(8), vipw(8) adduser(8)
User information should (and eventually will) be stored elsewhere.
7th Edition May 8, 1989 PASSWD(5)