bash-3.1$ whoami
apache
bash-3.1$ ls -l
total 164
-rw-rw---- 1 apache apache 25878 Nov 17 10:24 after-hours.wav
-rw-rw---- 1 apache apache 55696 Nov 17 11:36 all-circuits-busy-now.wav
-rw-rw---- 1 apache apache 30138 Nov 17 13:28 dnd-bypass.wav
-rw-rw---- 1 apache apache 44440 Nov 17 13:36 ent-target-attendant.wav
bash-3.1$ chgrp asterisk after-hours.wav
chgrp: changing group of `after-hours.wav': Operation not permitted
bash-3.1$