GPASSWD(1)

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

ÜBERSICHT

gpasswd [option] group

BESCHREIBUNG

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.

  Hinweise zu Gruppenpasswörtern

Gruppenpasswörter bergen ein Sicherheitsrisiko, da mehrere Personen das Passwort kennen. Dennoch sind Gruppen ein nützliches Mittel für die Zusammenarbeit zwischen Benutzern.

OPTIONEN

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
    zeigt die Hilfe an und beendet das Programm.

-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,...
    definiert eine Liste von Benutzern als Gruppenverwalter

-M, --members user,...
    definiert eine Liste von Benutzern als Gruppenmitglieder

WARNUNGEN

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.

KONFIGURATION

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).

    Der Standardwert ist 0, was bedeutet, dass die Anzahl der Mitglieder einer Gruppe nicht begrenzt ist.

    Das Aufteilen von Gruppen ermöglicht es, Längenvorgaben für die Zeilen der Gruppendatei einzuhalten. Damit kann sichergestellt werden, dass die Zeilen für NIS-Gruppen nicht länger als 1024 Zeichen sind.

    Falls Sie eine solche Begrenzung benötigen, können Sie 25 verwenden.

    Hinweis: Mit aufgeteilten Gruppen können möglicherweise nicht alle Hilfsprogramme (nicht einmal jene der Shadow-Programmsammlung) umgehen. Sie sollten diese Variable nur setzen, wenn Sie sie wirklich benötigen.

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.

    Die Werte müssen zwischen 1000 und 999.999.999 liegen.

    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.

DATEIEN

/etc/group
    Informationen zu den Gruppenkonten

/etc/gshadow
    geschützte Informationen zu den Gruppenkonten

SIEHE AUCH

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