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NAME

passwd — modify a user's password

SYNOPSIS

DESCRIPTION

passwd changes the user's local, Kerberos, or YP password. First, the user is prompted for their current password. If the current password is correctly typed, a new password is requested. The new password must be entered twice to avoid typing errors.

The new password should be at least six characters long and not purely alphabetic. Its total length must be less than _PASSWORD_LEN (currently 128 characters). A mixture of both lower and uppercase letters, numbers, and meta-characters is encouraged.

The quality of the password can be enforced by specifying an external checking program via the “passwordcheck” variable in login.conf(5).

The options are as follows:

-K

Forces the change to affect the Kerberos 5 database, even if the user has a password in the local database. Once the password has been verified, passwd communicates the new password information to the Kerberos authenticating host.

The user argument specifies a principal and optional realm, for example “user@DOMAIN.COM”.

-l

Causes the password to be updated only in the local password file. When changing only the local password, pwd_mkdb(8) is used to update the password databases.

-y

Forces the YP password database entry to be changed, even if the user has an entry in the local database. The rpc.yppasswdd(8) daemon should be running on the YP master server.

This is the behavior if no flags are specified: if Kerberos is active then passwd will talk to the Kerberos server (even if the user has an entry in the local database). If the password is not in the local password database, then an attempt is made to use the YP database.

The superuser is not required to provide a user's current password if only the local password is modified.

Which type of cipher is used to encrypt the password information depends on the configuration in login.conf(5). It can be different for local (“localcipher”) and YP (“ypcipher”) passwords. If none is specified, then blowfish with 6 rounds is used for local (“localcipher”) and old is used for YP (“ypcipher”) by default.

FILES

/etc/login.conf

configuration options

/etc/master.passwd

user database

/etc/passwd

user database, with confidential information removed

/etc/passwd.XXXXXX

temporary copy of the password file

/etc/ptmp

lock file for the passwd database

DIAGNOSTICS

Attempting to lock password file, please wait or press ^C to abort

The password file is currently locked by another process; passwd will keep trying to lock the password file until it succeeds or you hit the interrupt character (control-C by default). If passwd is interrupted while trying to gain the lock the password change will be lost.

If the process holding the lock was prematurely terminated the lock file may be stale and passwd will wait forever trying to lock the password file. To determine whether a live process is actually holding the lock, the admin may run the following:

$ fstat /etc/ptmp

If no process is listed, it is safe to remove the /etc/ptmp file to clear the error.

SEE ALSO

chpass(1), encrypt(1), kinit(1), login(1), login.conf(5), passwd(5), pwd_mkdb(8), vipw(8)

Robert Morris and Ken Thompson, UNIX password security.

HISTORY

A passwd command appeared in Version 3 AT&T UNIX.