It can be done with either one of these

sudo apt-get --purge remove gnome-desktop-environment


or

sudo apt-get --purge remove gnome-*


And there are probably even more methods. Re-installing, without formatting if you want to preserve settings, is most likely less time consuming though.

If you want to change the kernel you need to install these files:

linux-server
linux-headers-2.6.38-10-server
linux-headers-server
linux-image-2.6.38-10-server
linux-image-server
linux-restricted-modules-2.6.38-10-server
linux-restricted-modules-server
linux-ubuntu-modules-2.6.38-10-server


where 2.6.38-10 is the kernel version (change it to the one you are installing). And to remove the desktop kernel:

linux-generic
linux-headers-2.6.38-10-generic
linux-headers-generic
linux-image-2.6.38-10-generic
linux-image-generic
linux-restricted-modules-2.6.38-10-generic
linux-restricted-modules-generic
linux-ubuntu-modules-2.6.38-10-generic


Change 2.6.38-10 to the one you are using.

Warning: 


changing kernels can bork your system beyond any repair.
do not remove the old kernel before you can confirm the new one to work.
ofcourse untested


How can I switch from Desktop to Server without reinstalling via CD?
I have a view in Drupal 7 that lists people (users). It shows the username and the standard user picture field. If a user has a set image, it comes through perfectly. However, for users that didn't set a profile image no image is shown, even though I have a default profile image set in the people settings for the site.

How do I get views to use the default profile picture for people that do not have a profile image set?

Update: I wasn't clear. I know how to use the default image in the no results behavior. The issue is that I can't get the default image to use the imagestyle I use for the other images.
