gpasswd

Administer /etc/group and /etc/gshadow. More information: https://manned.org/gpasswd.

• Define group administrators:
  sudo gpasswd -A {{user1,user2}} {{group}}
• Set the list of group members:
  sudo gpasswd -M {{user1,user2}} {{group}}
• Create a password for the named group:
  gpasswd {{group}}
• Add a user to the named group:
  gpasswd -a {{user}} {{group}}
• Remove a user from the named group:
  gpasswd -d {{user}} {{group}}