modify a user's password
changes the user's local 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
(currently 128 characters). A
mixture of both lower and uppercase letters, numbers, and meta-characters is
The quality of the password can be enforced by specifying an external checking
program via the “passwordcheck” variable in
The options are as follows:
- Causes the password to be updated only in the local password file. When
changing only the local password,
used to update the password databases.
- Forces the YP password database entry to be changed, even if the user has
an entry in the local database. The
daemon should be running on the YP master server.
If no flags are specified and 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
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.
- configuration options
- user database
- user database, with confidential information removed
- temporary copy of the password file
- lock file for the passwd database
- 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
interrupted while trying to gain the lock the password change will be
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:
If no process is listed, it is safe to remove the
/etc/ptmp file to clear the error.
Robert Morris and
Ken Thompson, Password security: a
case history, Communications of the ACM,
Issue 11, Volume 22,
command appeared in
Version 3 AT&T UNIX