I have a lab of iMac computers at work. Recently I have been Installing Kubuntu on them and during the setup I decided to assign them specific hostnames and IPs from DHCP rather than just let them pick up the generic numbered names that my DHCP server was handing out by default.
My DHCP server is dhcpd on OpenBSD. I configured it to reduce the generic name pool and added static assignments for all the iMac MACs.
Unfortunately, the systems already had leases. And releasing and renewing is not as easy in Kubuntu as in MacOS. Rebooting or disconnecting and reconnecting didn't pick up the new assignments and after a bit I realized that the server had cached the old leases and was renewing them rather than handing out the new static ones I had configured.
So for reference, here is what I did:
In OpenBSD, go through the /var/db/dhcpd.leases file and clean out the ones you don't want it to remember. Then `kill -HUP` the dhcpd process.
On the Kubuntu desktop, `sudo systemctl stop NetworkManager` , `sudo rm /var/lib/NetworkManager/*.lease`, and `sudo systemctl start NetworkManager`.
Then the client got its new assigned address lease and all was well.
