Ubuntu Manpage: chgpasswd - Mettre à jour par lot des mots de passe des groupes

Provided by: passwd_4.17.4-2ubuntu2_amd64

NOM

       chgpasswd - Mettre à jour par lot des mots de passe des groupes

SYNOPSIS


       chgpasswd [options]

DESCRIPTION

       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.

       Cette commande est destinée aux gros systèmes pour lesquels un nombre importants de comptes sont créés en
       une seule fois.

OPTIONS

The options which apply to the chgpasswd command are:

-c, --crypt-method
Utiliser la méthode précisée pour chiffrer les mots de passe.

The available methods are DES, MD5, SHA256, SHA512, YESCRYPT and NONE if your libc supports these
methods.

-e, --encrypted
Indiquer que les mots de passe fournis sont chiffrés.

-h, --help
Afficher un message d'aide et quitter.

-m, --md5
Permettre d'utiliser le chiffrement MD5, plutôt que DES, lorsque les mots de passe fournis ne sont
pas chiffrés.

-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.

-s, --sha-rounds
Utiliser le nombre de rounds précisé pour chiffrer les mots de passe.

You can only use this option with crypt method: SHA256 SHA512 YESCRYPT

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.

By default, the number of rounds for YESCRYPT is defined by the YESCRYPT_COST_FACTOR in
/etc/login.defs.

A minimal value of 1 and a maximal value of 11 will be enforced for YESCRYPT. The default number of
rounds is 5.

AVERTISSEMENTS

       Pensez à configurer les permissions ou umask afin d'empêcher la lecture des fichiers non chiffrés par les
       d'autres utilisateurs.

       Vous devez vous assurer que les mots de passe et la méthode de chiffrement respectent la politique de mot
       de passe du système.

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, YESCRYPT. MD5 and DES should not
be used for new hashes, see crypt(5) for recommendations.

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.

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.

YESCRYPT_COST_FACTOR (number)
When ENCRYPT_METHOD is set to YESCRYPT, this defines the cost factor used by the encryption algorithm
by default (when the cost factor is not specified on the command line).

With a high cost factor, it is more difficult to brute force the password. But note also that more
CPU resources will be needed to authenticate users.

The value must be inside the 1-11 range.

FICHIERS

       /etc/group
           Informations sur les groupes.

       /etc/gshadow
           Informations sécurisées sur les groupes.

       /etc/login.defs
           Configuration de la suite des mots de passe cachés « shadow password ».

VOIR AUSSI

       gpasswd(1), groupadd(8), login.defs(5).

shadow-utils 4.17.4                                06/09/2025                                       CHGPASSWD(8)