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NAME

passwd — modify a user's password

SYNOPSIS

DESCRIPTION

passwd changes the user's password. If no user is specified, the user's login name is used (see logname(1)). 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 superuser is not required to provide a user's current password if only the local password is modified.

Password encryption parameters depend on the configuration of the “localcipher” capability in login.conf(5). If none is specified then blowfish is used, with the number of rounds selected based on system performance.

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), logname(1), login.conf(5), passwd(5), pwd_mkdb(8), vipw(8)

Robert Morris and Ken Thompson, Password security: a case history, Communications of the ACM, Issue 11, Volume 22, pp. 594–597, Nov. 1979.

HISTORY

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