| PASSWD(1) | User Commands | PASSWD(1) |
.SH "NAME" passwd - change user password
.SH "SYNOPSIS"
.HP 168u
passwd
[options]
[LOGIN]
.SH "DESCRIPTION"
.PP The passwd command changes passwords for user accounts. A regular
user can only change the password for their own account, while the superuser
can change the password for any account. The passwd also changes the
account or associated password validity period.
.SS "Password Changes"
.PP If the account has a non-empty password, the user is first prompted to
enter their current password. The entered password is encrypted and compared
to the stored value. The user has only one attempt to enter the correct
password. The superuser can bypass this step to allow changing forgotten
passwords.
.PP After the password has been entered, password aging information is
checked to determine if the user is permitted to change the password at this
time. If not, passwd refuses to change the password and exits.
.PP The user is then prompted twice for a replacement password. The second
entry is compared against the first and both are required to match for the
password to be changed.
.PP Then, the password is tested for complexity. passwd rejects
passwords that do not meet the complexity requirements. Do not include the
system default erase or kill characters.
.SS "Hints for user passwords"
.PP The security of a password depends on the strength of the hashing method
and the size of the key space. The hashing method can be selected with
ENCRYPT_METHOD. The size of the key space depends on the randomness
of the selected password.
.PP Compromises in password security normally result from careless password
selection or handling. For this reason, you should not select a password
which appears in a dictionary or one that must be written down. The password
should also not be a proper name, your license number, birth date, or street
address. Any of these may be used as guesses to violate system security.
.PP As a general guideline, passwords should be long and random. It's fine to
use simple character sets, such as passwords consisting only of lowercase
letters, if that helps memorizing longer passwords. For a password
consisting only of lowercase English letters randomly chosen, and a length
of 32, there are 26^32 (approximately 2^150) different possible
combinations. Being an exponential equation, it's apparent that the exponent
(the length) is more important than the base (the size of the character
set).
.PP You can find advice on how to choose a strong password on
https://en.wikipedia.org/wiki/Password_strength
.SH "OPTIONS"
.PP The options which apply to the passwd command are:
.PP -a, --all
This option can be used only with -S and causes show status for all users.
.RE
.PP -d, --delete
Deletes a user's password, making it empty. This command sets the account to be passwordless.
.RE
.PP -e, --expire
Immediately expire an account's password. This in effect can force a user to change their password at the user's next login.
.RE
.PP -h, --help
Display help message and exit.
.RE
.PP -i, --inactive INACTIVE
This option is used to disable an account after the password has been expired for a number of days. After a user account has had an expired password for INACTIVE days, the user may no longer sign on to the account.
.RE
.PP -k, --keep-tokens
Indicate password change should be performed only for expired authentication tokens (passwords). The user wishes to keep their non-expired tokens as before.
.RE
.PP -l, --lock
Lock the password of the named account. This option disables a password by changing it to a value which matches no possible encrypted value (it adds a ´!´ at the beginning of the password).
Note that this does not disable the account. The user may still be able to login using another authentication token (e.g. an SSH key). To disable the account, administrators should use usermod --expiredate 1 (this sets the account's expire date to 1970-01-02).
Users with a locked password are not allowed to change their password.
.RE
.PP -q, --quiet
Quiet mode.
.RE
.PP -r, --repository REPOSITORY
change password in REPOSITORY repository
.RE
.PP -R, --root CHROOT_DIR
Apply changes in the CHROOT_DIR directory and use the configuration files from the CHROOT_DIR directory. Only absolute paths are supported. No SELINUX support.
.RE
.PP -P, --prefix PREFIX_DIR
Apply changes to configuration files under the root filesystem found under the directory PREFIX_DIR. This option does not chroot and is intended for preparing a cross-compilation target. Some limitations: NIS and LDAP users/groups are not verified. No PAM support. No SELINUX support.
.RE
.PP -S, --status
Display account status information. The status information consists of 7 fields. The first field is the user's login name. The second field indicates if the user account has a locked password (L), has no password (NP), or has a usable password (P). The third field gives the date of the last password change. The next four fields are the minimum age, maximum age, warning period, and inactivity period for the password. These ages are expressed in days.
.RE
.PP -u, --unlock
Unlock the password of the named account. This option re-enables a password by changing the password back to its previous value (to the value before using the -l option).
.RE
.PP -w, --warndays WARN_DAYS
Set the number of days of warning before a password change is required. The WARN_DAYS option is the number of days prior to password expiration during which the user is warned that their password is about to expire.
.RE
.PP -x, --maxdays MAX_DAYS
Set the maximum number of days a password remains valid. After MAX_DAYS, the password is required to be changed.
Passing the number -1 as MAX_DAYS will remove checking a password's validity.
.RE
.PP -s, --stdin
This option is used to indicate that passwd should read the new password from standard input, which can be a pipe.
.RE
.SH "CAVEATS"
.PP Password complexity checking may vary from site to site. The user is
urged to select a password as complex as he or she feels comfortable
with.
.PP Users may not be able to change their password on a system if NIS is
enabled and they are not logged into the NIS server.
.PP passwd uses PAM to authenticate users and to change their
passwords.
.SH "FILES"
.PP /etc/passwd
User account information.
.RE
.PP /etc/shadow
Secure user account information.
.RE
.PP /etc/pam.d/passwd
PAM configuration for passwd.
.RE
.SH "EXIT VALUES"
.PP The passwd command exits with the following values:
.PP 0
success
.RE .PP 1
permission denied
.RE .PP 2
invalid combination of options
.RE .PP 3
unexpected failure, nothing done
.RE .PP 4
unexpected failure, passwd file missing
.RE .PP 5
passwd file busy, try again
.RE .PP 6
invalid argument to option
.RE .PP 10
an error was returned by pam(3)
.RE
.SH "SEE ALSO"
.PP chpasswd(8), makepasswd(1), passwd(5),
shadow(5), usermod(8).
.PP The following web page comically (yet correctly) compares the strength of
two different methods for choosing a password:
"https://xkcd.com/936/"
| 10/27/2026 | shadow-utils 4.20.3 |