dhclient (isc-dhclient-4.2.3-P2) doesn't remove the /var/run/dhclient.pid file
create a project with dhclient 1. start dhclient 2. pid file is created by verifying with "cat /var/run/dhclient.pid" 3. issuing dhclient -x command 4. pid file is NOT deteled when verifying with "cat /var/run/dhclient.pid"