Possible Duplicate:
How to downgrade the Kernel on 11.10
My wifi used to work very well on ubuntu 10.04 with kernel 2.6.32.28. Now after I installed ubuntu 11.04 with the lastest kernel, my wifi (rt3090) not working anymore. Is it safe to downgrade the kernel?, if so, how to downgrade it?
I have done exactly this in the past when upgrading to 11.04 broke my ability to use JACK with my soundcard (although it is no longer a problem with the latest kernel).
I simply added the previous distribution's APT line to /etc/apt/sources.list (or in a separate file in /etc/apt/sources.list.d), e.g.
deb http://archive.ubuntu.com/ubuntu/ maverick-updates main restricted
After updating the package list in aptitude, the previous 2.6.32 kernel versions were available in the list. Adding the older repository does not break anything else because apt will not by default downgrade packages, and all of the previous distribution's packages are older or equal to currently-installed versions.
Also as Dananjaya says, if you upgraded from an earlier distribution you should still have the older kernels installed anyway. However, you may want to add the APT line as suggested above in order to get security updates for that older kernel.
This is one of many solutions to your question,
Did you upgraded to Ubuntu 11.04 from 10.10? If so kernel images of 10.10 should still be on your system. first run,
sudo apt-get install startupmanager
It will install the 'startupmanager', a useful tool to tweak system settings easily. After you've installed it, run
sudo startupmanager
You will see the main program window and under it's 'boot options' tab, you will see 'Default Operating System' dropdown. Choose your desired kernel image (provided your system have the Image) from that list and close the program. Reboot your Computer.
To check wether you booted the kernel you wanted, run this command in your terminal
uname -a
Hope this helps.
Earlier
Downgrade Kernel: How to downgrade the Kernel on 11.10
Upgrade kernel: How can I upgrade kernel to 3.1?
