group - user group file
/etc/group is an ASCII file which defines the groups to
which users belong. There is one entry per line, and each
line has the format:
The field descriptions are:
the name of the group.
the (encrypted) group password. If this field is
empty, no password is needed.
GID the numerical group ID.
all the group member's user names, separated by commas.
login(1), newgrp(1), passwd(5)