When I upgraded from Ubuntu 8.04 (Hardy) to Ubuntu 8.10 (Intrepid), a
dhclient-exit-hook script I wrote no longer functioned.
dhclient-script was previously used by dhclient so that whenever the dhcp
changed, it would reconfigure the interfaces, generate the /etc/resolv.conf, and
run scripts who’s intention is to modify the /etc/resolv.conf file based on the
dhcp settings. These scripts are located in the folders
/etc/dhcp3/dhclient-enter-hooks.d/ and /etc/dhcp3/dhclient-exit-hooks.d/.
Reading up on the problem,
thanks to perlhead on the Ubuntu Forums,
it appears that since NetworkManager did the same function as dhclient-script,
which got in the way of NetworkManager’s plugins, so dhclient-script was disabled.