[MAN] passwd

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PASSWD

Section: OpenSSL (1SSL)
Updated: 2022-07-04
Index Return to Main Contents

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NAME

openssl-passwd, passwd - compute password hashes  

SYNOPSIS

openssl passwd [-help] [-crypt] [-1] [-apr1] [-aixmd5] [-5] [-6] [-salt string] [-in file] [-stdin] [-noverify] [-quiet] [-table] [-rand file...] [-writerand file] {password}  

DESCRIPTION

The passwd command computes the hash of a password typed at run-time or the hash of each password in a list. The password list is taken from the named file for option -in file, from stdin for option -stdin, or from the command line, or from the terminal otherwise. The Unix standard algorithm crypt and the MD5-based BSD password algorithm 1, its Apache variant apr1, and its AIX variant are available.  

OPTIONS

-help

Print out a usage message.

-crypt

Use the crypt algorithm (default).

-1

Use the MD5 based BSD password algorithm 1.

-apr1

Use the apr1 algorithm (Apache variant of the BSD algorithm).

-aixmd5

Use the AIX MD5 algorithm (AIX variant of the BSD algorithm).

-5

-6

Use the SHA256 / SHA512 based algorithms defined by Ulrich Drepper. See <https://www.akkadia.org/drepper/SHA-crypt.txt>.

-salt string

Use the specified salt. When reading a password from the terminal, this implies -noverify.

-in file

Read passwords from file.

-stdin

Read passwords from stdin.

-noverify

Don't verify when reading a password from the terminal.

-quiet

Don't output warnings when passwords given at the command line are truncated.

-table

In the output list, prepend the cleartext password and a TAB character to each password hash.

-rand file...

A file or files containing random data used to seed the random number generator. Multiple files can be specified separated by an OS-dependent character. The separator is ; for MS-Windows, , for OpenVMS, and : for all others.

[-writerand file]

Writes random data to the specified file upon exit. This can be used with a subsequent -rand flag.

 

EXAMPLES

  % openssl passwd -crypt -salt xx password
  xxj31ZMTZzkVA

  % openssl passwd -1 -salt xxxxxxxx password
  $1$xxxxxxxx$UYCIxa628.9qXjpQCjM4a.

  % openssl passwd -apr1 -salt xxxxxxxx password
  $apr1$xxxxxxxx$dxHfLAsjHkDRmG83UXe8K0

  % openssl passwd -aixmd5 -salt xxxxxxxx password
  xxxxxxxx$8Oaipk/GPKhC64w/YVeFD/

 

COPYRIGHT

Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the ``License''). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

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Index

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

EXAMPLES

COPYRIGHT

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PASSWD

Section: User Commands (1)
Updated: 03/14/2022
Index Return to Main Contents

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NAME

passwd - change user password  

SYNOPSIS

passwd [options] [LOGIN]

 

DESCRIPTION

The passwd command changes passwords for user accounts. A normal user may only change the password for his/her own account, while the superuser may change the password for any account. passwd also changes the account or associated password validity period.  

Password Changes

The user is first prompted for his/her old password, if one is present. This password is then encrypted and compared against the stored password. The user has only one chance to enter the correct password. The superuser is permitted to bypass this step so that forgotten passwords may be changed.

After the password has been entered, password aging information is checked to see if the user is permitted to change the password at this time. If not, passwd refuses to change the password and exits.

The user is then prompted twice for a replacement password. The second entry is compared against the first and both are required to match in order for the password to be changed.

Then, the password is tested for complexity. As a general guideline, passwords should consist of 6 to 8 characters including one or more characters from each of the following sets:

• lower case alphabetics

• digits 0 thru 9

• punctuation marks

Care must be taken not to include the system default erase or kill characters. passwd will reject any password which is not suitably complex.  

Hints for user passwords

The security of a password depends upon the strength of the encryption algorithm and the size of the key space. The legacy UNIX System encryption method is based on the NBS DES algorithm. More recent methods are now recommended (see ENCRYPT_METHOD). The size of the key space depends upon the randomness of the password which is selected.

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 which 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.

You can find advice on how to choose a strong password on http://en.wikipedia.org/wiki/Password_strength  

OPTIONS

The options which apply to the passwd command are:

-a, --all

This option can be used only with -S and causes show status for all users.

-d, --delete

Delete a user's password (make it empty). This is a quick way to disable a password for an account. It will set the named account passwordless.

-e, --expire

Immediately expire an account's password. This in effect can force a user to change his/her password at the user's next login.

-h, --help

Display help message and exit.

-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.

-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.

-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 set the account's expire date to Jan 2, 1970).

Users with a locked password are not allowed to change their password.

-n, --mindays MIN_DAYS

Set the minimum number of days between password changes to MIN_DAYS. A value of zero for this field indicates that the user may change his/her password at any time.

-q, --quiet

Quiet mode.

-r, --repository REPOSITORY

change password in REPOSITORY repository

-R, --root CHROOT_DIR

Apply changes in the CHROOT_DIR directory and use the configuration files from the CHROOT_DIR directory.

-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.

-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).

-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 the password expiring that a user will be warned that his/her password is about to expire.

-x, --maxdays MAX_DAYS

Set the maximum number of days a password remains valid. After MAX_DAYS, the password is required to be changed.

 

CAVEATS

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.

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.

passwd uses PAM to authenticate users and to change their passwords.  

FILES

/etc/passwd

User account information.

/etc/shadow

Secure user account information.

/etc/pam.d/passwd

PAM configuration for passwd.

 

EXIT VALUES

The passwd command exits with the following values:

0

success

1

permission denied

2

invalid combination of options

3

unexpected failure, nothing done

4

unexpected failure, passwd file missing

5

passwd file busy, try again

6

invalid argument to option

 

SEE ALSO

chpasswd(8), passwd(5), shadow(5), usermod(8).

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Index

NAME

SYNOPSIS

DESCRIPTION

Password Changes

Hints for user passwords

OPTIONS

CAVEATS

FILES

EXIT VALUES

SEE ALSO

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PASSWD

Section: File Formats and Conversions (5)
Updated: 03/14/2022
Index Return to Main Contents

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NAME

passwd - the password file  

DESCRIPTION

/etc/passwd contains one line for each user account, with seven fields delimited by colons (":"). These fields are:

• login name

• optional encrypted password

• numerical user ID

• numerical group ID

• user name or comment field

• user home directory

• optional user command interpreter

The encrypted password field may be blank, in which case no password is required to authenticate as the specified login name. However, some applications which read the /etc/passwd file may decide not to permit any access at all if the password field is blank. If the password field is a lower-case "x", then the encrypted password is actually stored in the shadow(5) file instead; there must be a corresponding line in the /etc/shadow file, or else the user account is invalid. If the password field is any other string, then it will be treated as an encrypted password, as specified by crypt(3).

The comment field is used by various system utilities, such as finger(1).

The home directory field provides the name of the initial working directory. The login program uses this information to set the value of the $HOME environmental variable.

The command interpreter field provides the name of the user's command language interpreter, or the name of the initial program to execute. The login program uses this information to set the value of the $SHELL environmental variable. If this field is empty, it defaults to the value /bin/sh.  

FILES

/etc/passwd

User account information.

/etc/shadow

optional encrypted password file

/etc/passwd-

Backup file for /etc/passwd.

Note that this file is used by the tools of the shadow toolsuite, but not by all user and password management tools.

 

SEE ALSO

crypt(3), getent(1), getpwnam(3), login(1), passwd(1), pwck(8), pwconv(8), pwunconv(8), shadow(5), su(1), sulogin(8).

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Index

NAME

DESCRIPTION

FILES

SEE ALSO

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Time: 04:45:54 GMT, September 16, 2022