For customers who want to deploy Ubuntu Server in an enterprise environment, Dell recommends that they use an LTS (Long Term Support) release of Ubuntu Server, which is currently v14.04, released in April 2014. The previous LTS release (v12.04) was originally released in April 2012. LTS releases have a support life cycle of 5 years, as opposed to non-LTS releases, which are only supported for 9 months.
LTS point releases are follow-up releases to the original LTS release. Some of these point releases are based on newer kernels which contain newer drivers and support newer hardware. The Ubuntu LTS releases 12.04.0 and 12.04.1 are based on the 3.2 kernel, the 12.04.2 release is based on the 3.5 kernel, the 12.04.3 release is based on the 3.8 kernel and the 12.04.4 release is based on the 3.11 kernel. The first point release (v14.04.1) for 14.04 will be released in August 2014.
If you originally installed any of releases 12.04.0 through 12.04.3 and then upgrade to the latest 12.04.4 via "apt-get upgrade", the kernel will NOT be automatically upgraded to 3.11. This is to ensure stability in your environment, since such a kernel upgrade can introduce unwanted instability: in a production environment, you usually only care about bug fixes and security updates.
What if you have Ubuntu 12.04 deployed and want to upgrade to the latest kernel? Say that you have a new hardware device (i.e. network controller) that is not supported with the 3.2 kernel, but it’s enabled with the 3.11 kernel?
To upgrade to the latest kernel, install the following packages:
$ sudo apt-get install linux-generic-lts-saucy xserver-xorg-lts-saucy
Verify that the new kernel is your default boot kernel, and reboot your machine. As with any other Linux distribution, you always have the option to revert to an earlier kernel by editing your boot loader configuration file.