x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
CHPASSWD(8) System Management Commands CHPASSWD(8)
NAME
chpasswd - update passwords in batch mode
SYNOPSIS
chpasswd [options]
DESCRIPTION
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:
user_name:password
By default the passwords must be supplied in clear-text, and are
encrypted by chpasswd. Also the password age will be updated, if
present.
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 overwritten 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 occurred for any user.
This command is intended to be used in a large system environment where
many accounts are created at a single time.
OPTIONS
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, SHA256, SHA512 and NONE if your
libc supports 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.
-e, --encrypted
Supplied passwords are in encrypted form.
-h, --help
Display help message and exit.
-m, --md5
Use MD5 encryption instead of DES when the supplied passwords are
not encrypted.
-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.
-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. PAM
authentication is using the host files. No SELINUX support.
-s, --sha-rounds ROUNDS
Use the specified number of rounds to encrypt the passwords.
You can only use this option with crypt method: SHA256 SHA512
By default, the number of rounds for SHA256 or SHA512 is defined by
the SHA_CRYPT_MIN_ROUNDS and SHA_CRYPT_MAX_ROUNDS variables in
/etc/login.defs.
A minimal value of 1000 and a maximal value of 999,999,999 will be
enforced for SHA256 and SHA512. The default number of rounds is
5000.
CAVEATS
Remember to set permissions or umask to prevent readability of
unencrypted files by other users.
CONFIGURATION
The following configuration variables in /etc/login.defs change the
behavior of this tool:
ENCRYPT_METHOD (string)
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,
SHA512. MD5 and DES should not be used for new hashes, see crypt(5)
for recommendations.
Note: this parameter overrides the MD5_CRYPT_ENAB variable.
MD5_CRYPT_ENAB (boolean)
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
no.
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 force the
password. But note also that more CPU resources will be needed to
authenticate users.
If not specified, the libc will choose the default number of rounds
(5000), which is orders of magnitude too low for modern hardware.
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.
FILES
/etc/passwd
User account information.
/etc/shadow
Secure user account information.
/etc/login.defs
Shadow password suite configuration.
SEE ALSO
passwd(1), newusers(8), login.defs(5), useradd(8).
shadow-utils 4.17.2 01/11/2025 CHPASSWD(8)
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