Ensure all groups in /etc/passwd exist in /etc/group

bad=""
for gid in $(awk -F: '{print $4}' /etc/passwd | sort -u); do
  getent group "$gid" >/dev/null 2>&1 || bad="$bad $gid"
done
if [ -n "$bad" ]; then echo "FAIL: GIDs with no group:$bad"; exit 1; fi
echo "OK: all passwd primary GIDs resolve to a group"; exit 0

expected_exit:

0

note:

Create missing groups or update user primary group assignments