GPASSWDSection: User Commands (1)
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NAMEgpasswd - administer /etc/group and /etc/gshadow
- gpasswd [option] group
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 about group passwords
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.
- Remove the password from the named group. Only group members will be allowed to use newgrp to join the named group.
- Restrict the access to the named group. Only group members will be allowed to use newgrp to join the named group.
-A, --administrators user,...
- Set the list of administrative users.
-M, --members user,...
- Set the list of group members.
The following configuration variables in /etc/login.defs change the behavior of this tool:
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.
Maximum members per group entry. When the maximum is reached, a new group entry (line) is started in
(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.
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
if you need to copy encrypted passwords to other systems which don't understand the new algorithm. Default is
This variable is superceded 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)
is set to
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 1000-999999999 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.
- Group account information.
- Secure group account information.
This document was created by man2html, using the manual pages.
Time: 05:29:04 GMT, December 24, 2015