I can't reproduce this. I have 3.10.0-2.9-generic, apparmor 2.8.0-0ubuntu19, and isc-dhcp-client 4.2.4-6ubuntu3. I tried in a VM by disabling networking in network-manager and adjusting /etc/network/interfaces to use 'iface eth0 inet dhcp' and using 'ifup eth0'. I also tried by using 'dhclient -sf /sbin/dhclient-script eth0'.
What is the contents of /etc/network/interfaces? Is /sbin/dhclient-script executable? Can you give the output of 'ls -R /etc/dhcp'?
I can't reproduce this. I have 3.10.0-2.9-generic, apparmor 2.8.0-0ubuntu19, and isc-dhcp-client 4.2.4-6ubuntu3. I tried in a VM by disabling networking in network-manager and adjusting /etc/network/ interfaces to use 'iface eth0 inet dhcp' and using 'ifup eth0'. I also tried by using 'dhclient -sf /sbin/dhclient- script eth0'.
What is the contents of /etc/network/ interfaces? Is /sbin/dhclient- script executable? Can you give the output of 'ls -R /etc/dhcp'?