GPASSWD(1)                       User Commands                      GPASSWD(1)

NOM
       gpasswd - administer /etc/group and /etc/gshadow

SYNOPSIS
       gpasswd [option] group

DESCRIPTION
       The gpasswd command is used to administer /etc/group, and /etc/gshadow.
       Every group can have administrators, members and a password.

       System administrators can use the -A option to define group
       administrator(s) and the -M option to define members. They have all
       rights of group administrators and members.

       gpasswd called by a group administrator with a group name only prompts
       for the new password of the group.

       If a password is set the members can still use newgrp(1) without a
       password, and non-members must supply the password.

   Notes sur les mots de passe de groupe
       Les mots de passe de groupe representent naturellement un risque en
       matiere de securite, puisque plusieurs personnes ont connaissance du
       mot de passe. Cependant, les groupes sont utiles pour permettre la
       cooperation entre differents utilisateurs.

OPTIONS
       Except for the -A and -M options, the options cannot be combined.

       The options which apply to the gpasswd command are:

       -a, --add user
           Add the user to the named group.

       -d, --delete user
           Remove the user from the named group.

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

       -Q, --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.

       -r, --remove-password
           Remove the password from the named group. The group password will
           be empty. Only group members will be allowed to use newgrp to join
           the named group.

       -R, --restrict
           Restrict the access to the named group. The group password is set
           to "!". Only group members with a password will be allowed to use
           newgrp to join the named group.

       -A, --administrators user,...
           Configurer la liste des administrateurs.

       -M, --members user,...
           Configurer la liste des membres du groupe.

AVERTISSEMENTS
       This tool only operates on the /etc/group and /etc/gshadow files.  Thus
       you cannot change any NIS or LDAP group. This must be performed on the
       corresponding server.

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

           Cette fonctionnalite (groupe decoupe) 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 caracteres.

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

           Remarque : les groupes decoupes ne sont peut-etre pas pris en
           charge par tous les outils (meme 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 etre 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.

FICHIERS
       /etc/group
           Informations sur les groupes.

       /etc/gshadow
           Informations securisees sur les groupes.

VOIR AUSSI
       newgrp(1), groupadd(8), groupdel(8), groupmod(8), grpck(8), group(5),
       gshadow(5).

shadow-utils 4.20.0               30/07/2026                        GPASSWD(1)