/etc/gshadow

/etc/gshadow  stores group passwords – a not that often used feature

The UNIX file that contains the account information, such as username, password, login directory, and default shell. All normal users on the system can read this file. Key point: The passwords are encrypted, so even though everyone can read the file, it doesn’t automatically guarantee access to the system.

group_name:password:GID:user_list

DESCRIPTION
/etc/group is a text file which defines the groups on the system. There is one entry per line, with the following format:

The field descriptions are:

group_name  – the name of the group.

password – the (encrypted) group password. If this field is empty, no password is needed.

GID the numerical group ID.

user_list – a list of the usernames that are members of this group, sepa- rated by commas.