CHGPASSWD(8)

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 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 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.

-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. No SELINUX support.

-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 is specified on the command line).

    It can take one of these values: SHA256, SHA512 (default), YESCRYPT. See crypt(5) for recommendations.

    Note: this only affects 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.

    History: This variable is used by other programs, which may still default to unsafe algorithms such as DES. To avoid using unsafe algorithms, the variable should always be specified.

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).

    La valeur par défaut est 0, ce qui signifie qu'il n'y a pas de limites pour le nombre de membres dans un groupe.

    Cette fonctionnalité (groupe découpé) permet de limiter la longueur des lignes dans le fichier de groupes. Ceci est utile pour s'assurer que les lignes pour les groupes NIS ne sont pas plus grandes que 1024 caractères.

    Si vous avez besoin de configurer cette limite, vous pouvez utiliser 25.

    Remarque : les groupes découpés ne sont peut-être pas pris en charge par tous les outils (même dans la suite d'outils Shadow). Vous ne devriez pas utiliser cette variable, sauf si vous en avez vraiment besoin.

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.

    Les valeurs doivent être comprises dans l'intervalle 1 000 - 999 999 999.

    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.

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.

    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.

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).