When I make changes to dhclient.conf such as modifying the DNS search path (so that the changes don't get lost on reboot or DHCP renews), how do I regenerate /etc/resolv.conf? That page suggests dhclient -r; dhclient which releases the address, thus disrupting my connection and preventing me from reaching the host again. Is there another way of doing this? Thanks.
Just use your favorite editor to edit /etc/resolv.conf (or /run/resolvconf/resolv.conf if you are running Ubuntu 12.04 or later with resolvconf active).
After a reboot or an interface downup cycle, resolv.conf should be correctly regenerated so that you can reconnect. If that isn't the case then you have another problem.