Ubuntu Upgrade Trounces Nvidia Video

After my last Ubuntu Linux (Dapper Drake 6.06) kernel upgrade, the Nvidia graphic display stopped working. When the system booted I wouldn't get a graphic login. If I went to a text screen and tried to start graphics manually (startx command) it would fail with an error:

Module nvidia not found

Here are the details from the /var/log/Xorg.0.log file:

(II) Setting vga for screen 0.
(**) NVIDIA(0): Depth 24, (--) framebuffer bpp 32
(==) NVIDIA(0): RGB weight 888
(==) NVIDIA(0): Default visual is TrueColor
(==) NVIDIA(0): Using gamma correction (1.0, 1.0, 1.0)
(**) NVIDIA(0): Enabling RENDER acceleration
(EE) NVIDIA(0): Failed to load the NVIDIA kernel module!
(EE) NVIDIA(0):  *** Aborting ***
(II) UnloadModule: "nvidia"
(II) UnloadModule: "ramdac"
(II) UnloadModule: "fb"
(EE) Screen(s) found, but none have a usable configuration.

Well, that was bizarre. The error says that the nvidia driver module isn't there. But it was there! Or at least, it was there and worked fine until I applied the kernel upgrade.

I didn't have time to debug the problem at the time, so I used a workaround. I ran dpkg-reconfigure xserver-xorg and switched from the (proprietary) accelerated nvidia driver to the dumb vesa frame buffer.

Tonight I finally got around to debugging the problem. Turns out the error message was right. The nvidia driver wasn't there. Or, more correctly, the right version of the driver wasn't there.

The problem is that when the kernel update was applied, the update process failred to retrieve the corresponding version of the proprietary drivers package (linux-restricted-modules). These two have to match. I was running kernel version 2.6.15-27 but my video driver was for version 2.6.15-26.

Here is the relevant output from dpkg -l that illustrates the problem:

ii  linux-image-2.6.15-26-k7              2.6.15-26.47
ii  linux-image-2.6.15-27-k7              2.6.15-27.48
ii  linux-image-k7                        2.6.15.25
ii  linux-restricted-modules-2.6.15-26-k7 2.6.15.11-4
ii  linux-restricted-modules-common       2.6.15.11-4

I fixed the problem by running:

aptitude install linux-restricted-modules-2.6.15-27-k7

This changed the installed packages to:

ii  linux-image-2.6.15-26-k7              2.6.15-26.47
ii  linux-image-2.6.15-27-k7              2.6.15-27.48
ii  linux-image-k7                        2.6.15.25
ii  linux-restricted-modules-2.6.15-26-k7 2.6.15.11-4
ii  linux-restricted-modules-2.6.15-27-k7 2.6.15.11-5
ii  linux-restricted-modules-common       2.6.15.11-5

With the updated video drivers installed, everything worked fine.

I don't understand why Ubuntu failed to pull down the video drivers when it upgraded the kernel. Fortunately, this manual fix solved the problem. Thought I'd blog it in case somebody runs into this difficulty.

I just hope that somebody doesn't turn out to be me at the next kernel update.