PASSWD(5)

NAME
passwd, master.passwd - format of the password file

DESCRIPTION
The passwd files are the local source of password information. They can be used in conjunction with the Hesiod domain ‘passwd’ and the NIS maps ‘passwd.byname’, ‘passwd.byuid’, ‘master.passwd.byname’, and ‘master.passwd.byuid’, as controlled by nsswitch.conf(5).

The master.passwd file is readable only by root, and consists of newline separated ASCII records, one per user, containing ten colon (“”): separated fields.

Each line has the form:
    name:password:uid:gid:class:change:expire:gecos:home_dir:shell

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 login class.
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.

Be aware that each line is limited to 1024 characters; longer ones will be ignored. This limit can be queried through sysconf(3) by using the _SC_GETPW_R_SIZE_MAX parameter.

The passwd file is generated from the master.passwd file by pwd_mkdb(8), has the class, change, and expire fields removed, and the password field replaced by a “*”.

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 nor dots (“”). be part of the name, as this tends to confuse 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. For the possible ciphers used in this field see passwd.conf(5).

The gid field is the group that the user will be placed in upon login. Since this system supports multiple groups (see groups(1)) this field currently has little special meaning.

The class field is a key for a user's login class. Login classes are defined in login.conf(5), which is a capfile(5) style database of user attributes, accounting, resource and environment settings.

The change field is the number of seconds from the epoch, UTC, until the password for the account must be changed. This field may be left empty to turn off the password aging feature. If this is set to “-1” then the user will be prompted to change their password at the next login.

The expire field is the number of seconds from the epoch, UTC, until the account expires. This field may be left empty to turn off the account aging feature.

If either of the change or expire fields are set, the system will remind the user of the impending change or expiry if they login within a configurable period (defaulting to 14 days) before the event.

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

The full name may contain an ampersand (“&”) which will be replaced by the capitalized login name when the gecos field is displayed or used by various programs such as finger(1), sendmail(1), etc.

The office and phone number subfields are used by the finger(1) program, and possibly other applications.

The user's home directory is the full UNIX path name where the user will be placed on login.

The shell field is the command interpreter the user prefers. If there is nothing in the shell field, the Bourne shell (/bin/sh) is assumed.

HESIOD SUPPORT
If ‘dns’ is specified for the ‘passwd’ database in nsswitch.conf(5), then passwd lookups occur from the ‘passwd’ Hesiod domain.

NIS SUPPORT
If ‘nis’ is specified for the ‘passwd’ database in nsswitch.conf(5), then passwd lookups occur from the ‘passwd.byname’, ‘passwd.byuid’, ‘master.passwd.byname’, and ‘master.passwd.byuid’ NIS maps.

COMPAT SUPPORT
If ‘compat’ is specified for the ‘passwd’ database, and either ‘dns’ or ‘nis’ is specified for the ‘passwd_compat’ database in nsswitch.conf(5), then the passwd file also supports standard ‘+/-’ exclusions and inclusions, based on user names and netgroups.

Lines beginning with a minus sign (“-”) are entries marked as being excluded from any following inclusions, which are marked with a plus sign (“+”).

If the second character of the line is an at sign (“@”), the operation involves the user fields of all entries in the netgroup specified by the remaining characters of the name field. Otherwise, the remainder of the name field is assumed to be a specific user name.

The “+” token may also be alone in the name field, which causes all users from either the Hesiod domain passwd (with ‘passwd_compat: dns’) or ‘passwd.byname’ and ‘passwd.byuid’ NIS maps (with ‘passwd_compat: nis’) to be included.

If the entry contains non-empty uid or gid fields, the specified numbers will override the information retrieved from the Hesiod domain or the NIS maps. As well, if the gecos, home_dir or shell entries contain text, it will override the information included via Hesiod or NIS. On some systems, the passwd field may also be overridden.

COMPATIBILITY
The password file format has changed since 4.3BSD. The following awk script can be used to convert your old-style password file into a new style password file. The additional fields “class”, “change” and “expire” are added, but are turned off by default. To set them, use the current day in seconds from the epoch + whatever number of seconds of offset you want.

    BEGIN { FS = ":"}
    { print $1 ":" $2 ":" $3 ":" $4 "::0:0:" $5 ":" $6 ":" $7 }

SEE ALSO
chpass(1), login(1), newgrp(1), passwd(1), pwhash(1), getpwent(3), login_getclass(3), login.conf(5), netgroup(5), passwd.conf(5), pwd_mkdb(8), useradd(8), vipw(8), yp(8)

(O'Reilly & Associates)

HISTORY
A passwd file format appeared in AT&T UNIX.

The NIS passwd file format first appeared in SunOS.

The Hesiod support first appeared in NetBSD 1.4.

The login.conf(5) capability first appeared in NetBSD 1.5.

BUGS
User information should (and eventually will) be stored elsewhere.

Placing ‘compat’ exclusions in the file after any inclusions will have unexpected results.