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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | CAVEATS | CONFIGURATION | FILES | SEE ALSO | COLOPHON |
GPASSWD(1) User Commands GPASSWD(1)
gpasswd - administer /etc/group and /etc/gshadow
gpasswd [option] group
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 about group passwords
Group passwords are an inherent security problem since more than one
person is permitted to know the password. However, groups are a
useful tool for permitting co-operation between different users.
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
Display help message and exit.
-Q, --root CHROOT_DIR
Apply changes in the CHROOT_DIR directory and use the
configuration files from the CHROOT_DIR directory.
-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,...
Set the list of administrative users.
-M, --members user,...
Set the list of group members.
This tool only operates on the /etc/groupand /etc/gshadow files.
Thus you cannot change any NIS or LDAP group. This must be performed
on the corresponding server.
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.
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.
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.
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 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 1000-999,999,999 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.
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.
/etc/group
Group account information.
/etc/gshadow
Secure group account information.
newgrp(1), groupadd(8), groupdel(8), groupmod(8), grpck(8), group(5),
gshadow(5).
This page is part of the shadow-utils (utilities for managing
accounts and shadow password files) project. Information about the
project can be found at ⟨http://pkg-shadow.alioth.debian.org/⟩. If
you have a bug report for this manual page, see
⟨http://pkg-shadow.alioth.debian.org/getinvolved.php⟩. This page was
obtained from the project's upstream Git repository
⟨git://anonscm.debian.org/git/pkg-shadow/shadow.git⟩ on 2017-07-05.
If you discover any rendering problems in this HTML version of the
page, or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the information
in this COLOPHON (which is not part of the original manual page),
send a mail to man-pages@man7.org
shadow-utils 4.4 07/05/2017 GPASSWD(1)
Pages that refer to this page: newgrp(1), sg(1), group(5), chgpasswd(8)