Recover From A Failed Custom Kernel
So you tried your hand in building your own custom kernel and it fails. Fret not as it is extremely easy to get it back to a working state. You just need to connect your keyboard and monitor back and change the boot sequence manually.If you like to experiment a lot, consider investing in a small LCD monitor (with SVGA and HDMI input).These monitors are compact and can be tucked away when not in use. (Above picture is provided as illustration only, it's not a recommendation).
Another approach is to spend the money and get a case with a built in monitor. The downside of a LCD case is the bulkiness, and the connection is not always internal (e.g. if your motherboard don't have a internal HDMI/VGA header you have to route the connection out externally). Given the price, this is not a practical solution, but it looks cool! :)Some motherboards support LVDS monitors but I havn't tried them yet.
Anyway, connect the monitor and keyboard, boot up the computer and hit any arrow key immediately until you see this screen. You only have a short window to do this, reboot the machine again if you are not quick enough. Once you see this screen, make sure the entry "Advanced options for Snakeoil GNU/Linux" is selected (see example below), and hit the "Enter" key.You should see something like this.Select the line that says "with Linux 3.0.3-rt12snakeoil" and press the "Enter" key. The machine should boot up fine now. If you are using a registered version of Snakeoil, upload another kernel to make it the default.
For others, login to the machine, remove the problem files, modify /etc/default/grub and remove the default line, and finish by running this command: "sudo update-grub".