The Ubuntu kernel PPA doesn't have kernel 3.1. Is there any other guaranteed way to upgrade because I don't want to reinstall Ubuntu again.
A bit earlier there was a question: How to downgrade the Kernel on 11.10. Upgrading the kernel is not harder.
You could download the kernel binaries from the old or new Ubuntu releases1. The Precise2 has the 3.1. Also the Kernel Mainline build3 has the 3.1.
Donwloading from the Mainline the linux-image-3.1.0-030100rc10-generic. Installing it. Rebooting with it and the (K)ubuntu 11.10 is running with the 3.1.
I think kernel team have uploaded the 3.1 kernel here http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.1-oneiric/
EDIT: three packages need to be installed.
The steps below only install two. This answer needs to be improved.
Kernel 3.1 is available. Here's How to install it :
wget http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.1-oneiric/linux-headers-3.1.0-030100_3.1.0-030100.201110241006_all.deb sudo dpkg -i linux-headers-3.1.0-030100_3.1.0-030100.201110241006_all.deb
For Ubuntu 11.10/11.04 (32-bit):
wget http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.1-oneiric/linux-headers-3.1.0-030100-generic_3.1.0-030100.201110241006_i386.deb sudo dpkg -i linux-headers-3.1.0-030100-generic_3.1.0-030100.201110241006_i386.deb
For Ubuntu 11.10/11.04 (64-bit):
wget http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.1-oneiric/linux-headers-3.1.0-030100-generic_3.1.0-030100.201110241006_amd64.deb sudo dpkg -i linux-headers-3.1.0-030100-generic_3.1.0-030100.201110241006_amd64.deb
But, Is it Safe to upgrade to Kernel 3.1 ? I Remember when I Upgraded from 2.6 to 3.0 on ubuntu 11.04 and My GPU Driver didn't work and there was no unity. I Don't want this to happen again.
I recommend don't try it.
Lately the new 3.x kernel seem bad and each release introduces more bugs than new features.
Since 3.10 NVidia hangs each time and 3.11 introduced the new "feature":
run-parts: executing /etc/kernel/header_postinst.d/dkms 3.1.1-030101-generic /boot/vmlinuz-3.1.1-030101-generic Error! Problems with depmod detected. Automatically uninstalling this module. DKMS: Install Failed (depmod problems). Module rolled back to built state.
Not sure what this means.