The Linux kernel is the core of the GNU/Linux system. Upgrading the kernel is a normal process one should perform every few months when a new stable release is released with bug fixes or even security fixes. Another reason might be to test the development versions of the kernel e.g. to take advantage of new drivers or optimizations - or just to validate the development-state or help bug-hunting.
We strongly suggest to use the T2 Linux kernel packages because you will miss some T2 Linux specific features or hot-fixes not yet in the official kernel. Also a lot "third-party" kernel modules, such as W-LAN, webcam and virtualization drivers are built in the T2 controlled kernel build automatically. You can update the kernel by just building it via ./t2 build or ./t2 install as usual.
The configuration for the kernel is performed automatically by parsing and merging the various configuration sources: the version of the package itself, architecture specific options, target specific options and user supplied values. You can define custom kernel configuration - and even disable the automatics - using ./t2 config. The kernel options are located in the expert section named 'Linux Kernel Options'. The possible styles of configuration generation are:
( ) Do not perform any automatic kernel configuration ( ) Perform normal kernel configuration without modules (X) Perform normal kernel configuration including modules
'Do not perform any automatic kernel configuration' will use the static configuration the user must supply either adding the rules in the configuration menu or by placing them manually in config/$id/linux.cfg. The last two options will use the full T2 Linux facilities to generate the configuration automatically - and so will also merge in user-supplied rules. 'Perform normal kernel configuration including modules' is the default.
For further information on how to compile the Linux kernel see \cite{KernelHowto}.