Code:

# cat /etc/group
users::100:owl
web:x:102:root

# cat /etc/passwd
owl:x:1000:102:,,,:/home/owl:/bin/bash

$ id
uid=1000(owl) gid=102(web) groups=102(web),100(users)

$ newgrp users
configuration error - unknown item 'CLOSE_SESSIONS' (notify administrator)