PASSWD(5) BSD File Formats Manual 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 (“:”) sepa‐
rated 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 con‐
trol 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 any‐
one 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 termcap(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 config‐
urable period (defaulting to 14 days) before the event.
The gecos field normally contains comma (“,”) separated subfields as fol‐
lows:
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(8), 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 inclu‐
sions, 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 sys‐
tems, the passwd field may also be overridden.
SEE ALSOchpass(1), login(1), newgrp(1), passwd(1), pwhash(1), getpwent(3),
login_getclass(3), login.conf(5), netgroup(5), passwd.conf(5),
adduser(8), pwd_mkdb(8), vipw(8), yp(8)
Managing NFS and NIS (O'Reilly & Associates)
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 }
HISTORY
A passwd file format appeared in Version 6 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.
BSD June 21, 2007 BSD
