/etc/gshadow contains the shadowed information for group accounts.
This file must not be readable by regular users if password security is to be maintained.
Each line of this file contains the following colon-separated fields:
If the password field contains some string that is not a valid result of crypt(3), for instance ! or *, users will not be able to use a unix password to access the group (but group members do not need the password).
The password is used when an user who is not a member of the group wants to gain the permissions of this group (see newgrp(1)).
This field may be empty, in which case only the group members can gain the group permissions.
A password field which starts with a exclamation mark means that the password is locked. The remaining characters on the line represent the password field before the password was locked.
This password supersedes any password specified in /etc/group.
Administrators can change the password or the members of the group.
Administrators also have the same permissions as the members (see below).
Members can access the group without being prompted for a password.
You should use the same list of users as in /etc/group.
gpasswd(5), group(5), grpck(8), grpconv(8), newgrp(1).