PASSWD(1) BSD General Commands Manual PASSWD(1)NAME
passwd, yppasswd — modify a user's password
SYNOPSISpasswd [-l] [user]
yppasswd [-l] [-y] [-d domain] [-h host] [-o]
The passwd utility changes the user's local, Kerberos, or NIS password.
If the user is not the super-user, passwd first prompts for the current
password and will not continue unless the correct password is entered.
When entering the new password, the characters entered do not echo, in
order to avoid the password being seen by a passer-by. The passwd util‐
ity prompts for the new password twice in order to detect typing errors.
The new password should be at least six characters long (which may be
overridden using the login.conf(5) “minpasswordlen” setting for a user's
login class) and not purely alphabetic. Its total length must be less
than _PASSWORD_LEN (currently 128 characters).
The new password should contain a mixture of upper and lower case charac‐
ters (which may be overridden using the login.conf(5) “mixpasswordcase”
setting for a user's login class). Allowing lower case passwords may be
useful where the password file will be used in situations where only
lower case passwords are permissible, such as when using Samba to authen‐
ticate Windows clients. In all other situations, numbers, upper case
letters and meta characters are encouraged.
Once the password has been verified, passwd communicates the new password
information to the Kerberos authenticating host.
The following option is available:
-l Cause the password to be updated only in the local password file,
and not with the Kerberos database. When changing only the local
password, pwd_mkdb(8) is used to update the password databases.
When changing local or NIS password, the next password change date is set
according to “passwordtime” capability in the user's login class.
To change another user's Kerberos password, one must first run kinit(1)
followed by passwd. The super-user is not required to provide a user's
current password if only the local password is modified.
The passwd utility has built-in support for NIS. If a user exists in the
NIS password database but does not exist locally, passwd automatically
switches into yppasswd mode. If the specified user does not exist in
either the local password database or the NIS password maps, passwd
returns an error.
When changing an NIS password, unprivileged users are required to provide
their old password for authentication (the rpc.yppasswdd(8) daemon
requires the original password before it will allow any changes to the
NIS password maps). This restriction applies even to the super-user,
with one important exception: the password authentication is bypassed for
the super-user on the NIS master server. This means that the super-user
on the NIS master server can make unrestricted changes to anyone's NIS
password. The super-user on NIS client systems and NIS slave servers
still needs to provide a password before the update will be processed.
The following additional options are supported for use with NIS:
-y Override passwd's checking heuristics and forces it into NIS
-l When NIS is enabled, the -l flag can be used to force passwd into
“local only” mode. This flag can be used to change the entry for
a local user when an NIS user exists with the same login name.
For example, you will sometimes find entries for system
“placeholder” users such as bin or daemon in both the NIS pass‐
word maps and the local user database. By default, passwd will
try to change the NIS password. The -l flag can be used to
change the local password instead.
Specify what domain to use when changing an NIS password. By
default, passwd assumes that the system default domain should be
used. This flag is primarily for use by the superuser on the NIS
master server: a single NIS server can support multiple domains.
It is also possible that the domainname on the NIS master may not
be set (it is not necessary for an NIS server to also be a
client) in which case the passwd command needs to be told what
domain to operate on.
Specify the name of an NIS server. This option, in conjunction
with the -d option, can be used to change an NIS password on a
non-local NIS server. When a domain is specified with the -d
option and passwd is unable to determine the name of the NIS mas‐
ter server (possibly because the local domainname is not set),
the name of the NIS master is assumed to be “localhost”. This
can be overridden with the -h flag. The specified hostname need
not be the name of an NIS master: the name of the NIS master for
a given map can be determined by querying any NIS server (master
or slave) in a domain, so specifying the name of a slave server
will work equally well.
-o Do not automatically override the password authentication checks
for the super-user on the NIS master server; assume “old” mode
instead. This flag is of limited practical use but is useful for
/etc/master.passwd the user database
/etc/passwd a Version 7 format password file
/etc/passwd.XXXXXX temporary copy of the password file
/etc/login.conf login class capabilities database
/etc/auth.conf configure authentication services
SEE ALSOchpass(1), kinit(1), login(1), login.conf(5), passwd(5), kerberos(8),
kpasswdd(8), pw(8), pwd_mkdb(8), vipw(8)
Robert Morris and Ken Thompson, UNIX password security.
The yppasswd command is really only a link to passwd.
A passwd command appeared in Version 6 AT&T UNIX.
BSD June 6, 1993 BSD