The ATI Radeon HD 5770 graphics card on my main desktop computer died recently after months and months of noisy overheated operation (not a gamer myself, the dust is the one to blame here). So I’ve recently upgraded the GPU and unfortunately, I also had to reinstall Ubuntu 12.04. After many failed attempts, I was unable to make the card work with the existing graphics stack (tried different versions of the AMD proprietary driver with no luck). Fortunately I have a separate /home partition, so reinstalling Ubuntu is not that much of a pain.
So I decided to re-install the system and I downloaded a fresh 12.04 image from Ubuntu’s website. Soon after the installation completed, I noticed that the new Ubuntu image came with an updated Linux kernel, one from the 3.5 series instead of the normal 3.2 that I was used to see on my old Ubuntu 12.04 installation. I doubled check with my laptop’s 12.04 install, and effectively, there I can see a 3.2 kernel.
It seems that Ubuntu is shipping its newer Ubuntu Desktop images with updated Linux kernel and X stacks, what they call the “LTS Hardware Enablement Stack“. This is happening since the 12.04.2 point release. Point releases 0 and 1 shipped with a 3.2 kernel. So if you have an old 12.04 LTS installation , any upgrades applied via the update-manager or apt-get will only ever install kernels from the 3.2 series.
It turns out that this is a policy that they plan to continue with in future 12.04 point releases, where the kernel and X stack will be aligned to the latest Ubuntu available at the time.
However, in order to get these newer kernels you either need to install a system from a 12.04.2+ image or alternatively, opt-in by manually running the following command that will upgrade your installation to the quantal enablement stack (the latest at the time of writing).
$ sudo apt-get install linux-generic-lts-quantal xserver-xorg-lts-quantal
In case anyone wonder, the fresh Ubuntu 12.04 installation fixed the problem I was experiencing with the graphics. But to be completely honest, I still don’t know exactly why it did.