Clearing out DHCP leases on (K)Ubuntu with dhcpd on OpenBSD.

 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.

Installing Kubuntu on Late-2015 iMacs

Recently I have been installing and configuring Kubuntu on several older 27" 5K Retina iMacs (17,1 Late-2015) that are no longer supported with software updates or security patches by Apple. They are beautiful systems and have no issues other than being abandoned by Apple.

 These iMacs boot with UEFI and holding the Option key when powering on will offer a choice of boot devices, including the Kubuntu installer USB I flashed from the ISO download.

 Actually booting into the Kubuntu installer was a bit of a challenge though because there is a display power management issue with the AMD graphics in these iMacs that requires passing `amdgpu.dpm=0` to the kernel as an option when booting. If you don't do it, you might *eventually* see *something* to show up, but everything will be extremely slow.

Getting that kernel option in place can be a bit tricky if you can't catch the Grub bootloader in time. One way that helped me was to install Ventoy on the USB stick and then copy the Kubuntu ISO to it. Ventoy gave me a "Boot Kubuntu via Grub2" boot option. That gave me a chance to catch Grub with the ESC key and then `e` to edit the options and put `amdgpu.dpm=0` inline with the `quiet` and `splash` options that are were already there.

Proceeding with the install should cause the installer to install grub with that kernel option in place. But if you want to double check or find any painfully slow boot/display issues later on, you can always make sure that option is set in /etc/default/grub and run update-grub to put it back in place.

Ubuntu Gnome Launcher Missing Application Icons

 Recently, my non-snap version of Element (Desktop) on Ubuntu 26.04 started behaving badly by not displaying its icon properly in the Gnome "Dash" (see Gnome Terminology).

Some searching revealed Fixing Applications Icon Missing from the Launcher in Ubuntu and that led me to a fix by editing /usr/share/applications/element-desktop.desktop to switch the StartupWMClass to element rather than Element.

Unfortunately, some time later (likely after applying updates to the element-desktop package) the behaviour reverted to the broken icon.

I took a guess that copying that /usr/share/applications/element-desktop.desktop file to my ~/.local/share/applications/ folder and fixing it there might override the broken one being installed and maintained by the package and survive future upgrades to the package.

 My first hunch was correct. It overrides and works. Time will tell if it persists. In the meantime, Element issue #33472 exists for the problem caused by a mismatched StartupWMClass.

On a related note: Element issue #34895 points to Electron issue #53215 for the broken status icon in the Gnome "Top Bar".