The options which apply to the groupmod command are:
-ggid The numerical value of the group’s ID. This value must be
unique, unless the -o option is used. The value must be
non-negative. Values between 0 and 999 are typically reserved
for system groups. Any files which the old group ID is the file
group ID must have the file group ID changed manually.
The name of the group will be changed from group to