groupmod —
modify an existing group on the system
  
    | groupmod | [ -ov] [-ggid] [-nnewname] group | 
The groupmod utility modifies an existing group on the
  system. See group(8) for more
  information about EXTENSIONS. The options are as
  follows:
  - -ggid
- Give the numeric group identifier to be used for the new group.
- -nnew-group-name
- Give the new name which the group shall have.
- -o
- Allow the new group to have a gid which is already in use for another
      group.
- -v
- Enable verbose mode - explain the commands as they are executed. This
      option is included if built with EXTENSIONS.
Thegroupmod utility exits 0 on success,
  and >0 if an error occurs.
The groupmod utility first appeared in
  NetBSD 1.5. It is based on the
  addnerd package by the same author.
The groupmod utility was written by
  Alistair G. Crooks ⟨agc@NetBSD.org⟩.