|
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | CAVEATS | CONFIGURATION | FILES | SEE ALSO | COLOPHON |
CHGPASSWD(8) System Management Commands CHGPASSWD(8)
chgpasswd - update group passwords in batch mode
chgpasswd [options]
The chgpasswd command reads a list of group name and password pairs
from standard input and uses this information to update a set of
existing groups. Each line is of the format:
group_name:password
By default the supplied password must be in clear-text, and is
encrypted by chgpasswd.
The default encryption algorithm can be defined for the system with
the ENCRYPT_METHOD variable of /etc/login.defs, and can be
overwritten with the -e, -m, or -c options.
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 chgpasswd command are:
-c, --crypt-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.
-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.
-s, --sha-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 enforced.
You can only use this option with the SHA256 or SHA512 crypt
method.
By default, the number of rounds is defined by the
SHA_CRYPT_MIN_ROUNDS and SHA_CRYPT_MAX_ROUNDS variables in
/etc/login.defs.
Remember to set permissions or umask to prevent readability of
unencrypted files by other users.
You should make sure the passwords and the encryption method respect
the system's password policy.
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.
Note: this parameter overrides the MD5_CRYPT_ENAB variable.
Note: This only affect the generation of group passwords. The
generation of user passwords is done by PAM and subject to the
PAM configuration. It is recommended to set this variable
consistently with the PAM configuration.
MAX_MEMBERS_PER_GROUP (number)
Maximum members per group entry. When the maximum is reached, a
new group entry (line) is started in /etc/group (with the same
name, same password, and same GID).
The default value is 0, meaning that there are no limits in the
number of members in a group.
This feature (split group) permits to limit the length of lines
in the group file. This is useful to make sure that lines for NIS
groups are not larger than 1024 characters.
If you need to enforce such limit, you can use 25.
Note: split groups may not be supported by all tools (even in the
Shadow toolsuite). You should not use this variable unless you
really need it.
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.
Note: This only affect the generation of group passwords. The
generation of user passwords is done by PAM and subject to the
PAM configuration. It is recommended to set this variable
consistently with the PAM configuration.
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
authenticate users.
If not specified, the libc will choose the default number of
rounds (5000).
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.
Note: This only affect the generation of group passwords. The
generation of user passwords is done by PAM and subject to the
PAM configuration. It is recommended to set this variable
consistently with the PAM configuration.
/etc/group
Group account information.
/etc/gshadow
Secure group account information.
/etc/login.defs
Shadow password suite configuration.
gpasswd(1), groupadd(8), login.defs(5).
This page is part of the shadow-utils (utilities for managing
accounts and shadow password files) project. Information about the
project can be found at ⟨http://pkg-shadow.alioth.debian.org/⟩. If
you have a bug report for this manual page, see
⟨http://pkg-shadow.alioth.debian.org/getinvolved.php⟩. This page was
obtained from the project's upstream Git repository
⟨git://anonscm.debian.org/git/pkg-shadow/shadow.git⟩ on 2017-07-05.
If you discover any rendering problems in this HTML version of the
page, or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the information
in this COLOPHON (which is not part of the original manual page),
send a mail to man-pages@man7.org
shadow-utils 4.4 07/05/2017 CHGPASSWD(8)