SIMULATION - Copy /etc/fstab to /var/tmp name admin, the user1 could read, write and modify it, while user2 without any permission. 

See explanation below.

# cp /etc/fstab /var/tmp/ # chgrp admin /var/tmp/fstab # setfacl -m u:user1:rwx /var/tmp/fstab # setfacl -m u:user2:--- /var/tmp/fstab # ls -l -rw-rw-r--+ 1 root admin 685 Nov 10 15:29 /var/tmp/fstab