CHPASSWD(8) System Management Commands CHPASSWD(8)NAMEchpasswd - update passwords in batch mode
The chpasswd command reads a list of user name and password pairs from
standard input and uses this information to update a group of existing
users. Each line is of the format:
By default the passwords must be supplied in clear-text, and are
encrypted by chpasswd. Also the password age will be updated, if
The default encryption algorithm can be defined for the system with the
ENCRYPT_METHOD or MD5_CRYPT_ENAB variables of /etc/login.defs, and can
be overwitten with the -e, -m, or -c options.
chpasswd first updates all the passwords in memory, and then commits
all the changes to disk if no errors occured for any user.
This command is intended to be used in a large system environment where
many accounts are created at a single time.
The options which apply to the chpasswd command are:
-c, --crypt-method METHOD
Use the specified method to encrypt the passwords.
The available methods are DES, MD5, NONE, and SHA256 or SHA512 if
your libc support these methods.
By default (if none of the -c, -m, or -e options are specified),
the encryption method is defined by the ENCRYPT_METHOD or
MD5_CRYPT_ENAB variables of /etc/login.defs.
Supplied passwords are in encrypted form.
Display help message and exit.
Use MD5 encryption instead of DES when the supplied passwords are
-R, --root CHROOT_DIR
Apply changes in the CHROOT_DIR directory and use the configuration
files from the CHROOT_DIR directory.
-s, --sha-rounds ROUNDS
Use the specified number of rounds to encrypt the passwords.
The value 0 means that the system will choose the default number of
rounds for the crypt method (5000).
A minimal value of 1000 and a maximal value of 999,999,999 will be
You can only use this option with the SHA256 or SHA512 crypt
By default, the number of rounds is defined by the
SHA_CRYPT_MIN_ROUNDS and SHA_CRYPT_MAX_ROUNDS variables in
Remember to set permissions or umask to prevent readability of
unencrypted files by other users.
The following configuration variables in /etc/login.defs change the
behavior of this tool:
This defines the system default encryption algorithm for encrypting
passwords (if no algorithm are specified on the command line).
It can take one of these values: DES (default), MD5, SHA256,
Note: this parameter overrides the MD5_CRYPT_ENAB variable.
Indicate if passwords must be encrypted using the MD5-based
algorithm. If set to yes, new passwords will be encrypted using the
MD5-based algorithm compatible with the one used by recent releases
of FreeBSD. It supports passwords of unlimited length and longer
salt strings. Set to no if you need to copy encrypted passwords to
other systems which don't understand the new algorithm. Default is
This variable is superseded by the ENCRYPT_METHOD variable or by
any command line option used to configure the encryption algorithm.
This variable is deprecated. You should use ENCRYPT_METHOD.
SHA_CRYPT_MIN_ROUNDS (number), SHA_CRYPT_MAX_ROUNDS (number)
When ENCRYPT_METHOD is set to SHA256 or SHA512, this defines the
number of SHA rounds used by the encryption algorithm by default
(when the number of rounds is not specified on the command line).
With a lot of rounds, it is more difficult to brute forcing the
password. But note also that more CPU resources will be needed to
If not specified, the libc will choose the default number of rounds
The values must be inside the 1000-999,999,999 range.
If only one of the SHA_CRYPT_MIN_ROUNDS or SHA_CRYPT_MAX_ROUNDS
values is set, then this value will be used.
If SHA_CRYPT_MIN_ROUNDS > SHA_CRYPT_MAX_ROUNDS, the highest value
will be used.
User account information.
Secure user account information.
Shadow password suite configuration.
SEE ALSOpasswd(1), newusers(8), login.defs(5), useradd(8).
shadow-utils 18.104.22.168 05/25/2012 CHPASSWD(8)