(Noob) Question about Kernels

[ZaKoNe]

Just reading about kernels and what they apparently do can someone explain to me exactly what they are and how they pair with the custom ROM? My current assumption is it changes the voltage/speed settings of the phone but I'm still pretty clueless and wanted to have a better understanding so I know what I'm adding to the phone when I root.

[Mitchel_nexusone]

From what I can figure, kernels are like a patch or add-on to an existing rom to change functionality. Undervolt, add home screens, change trackball lighting, add icons to the doc area, etc. To uninstall a kernel, one must wipe the os and reflash from a backup.

If I'm wrong, I'm sure someone will speak up.

With that said, always perform a backup before installing a kernel...

[thomaslkuo]

Kernel acts as a barrier between the Hardware and the software. The application calls on such and such to do such and such work, it will call on the kernel to do it. It is basically the traffic control, or the traffic cop that directs traffic. As part of its duty, it signals the amount of voltage that a CPU calls on when making computations. In this way, the kernel is the backbone of any Operating System, whether it is Microsoft, or Linux based such as Android.

While there are differnet kernels on the web, most build off the source code of Google and the custom rom it was built for, in many cases Cyanogen. Therefore it is important to make sure that the kernel was made for a specific ROM. Because if you did not, you could screw up the phone. While, maybe not permanently, it will make your phone unstable.

Hope this helps. If someone has addition to add, please help.

From what I can figure, kernels are like a patch or add-on to an existing rom to change functionality. Undervolt, add home screens, change trackball lighting, add icons to the doc area, etc. To uninstall a kernel, one must wipe the os and reflash from a backup.

If I'm wrong, I'm sure someone will speak up.

With that said, always perform a backup before installing a kernel...

[kc.rkitek]

Here's a pretty concise description what a kernel is:
Kernel (computing) - Wikipedia, the free encyclopedia

and here are some Android specific features:
Android Kernel Features - eLinux.org

I'm no comp sci guy, but here's my understanding of what it does...very basically, it is the bridge between apps and hardware...it manages processes/memory/cpu/filesystem, services resource requests from the processes and apps, and probably a lot more that i don't know about. And yes, it does obviously manage the clock speed and regulate voltage.

I don't know exactly how they relate to specific custom roms...it probably has a lot do with the kernel version the rom was built on and the processor optimizations that are written into the custom rom. Take CyanogenMod v5.0.6 for instance; it is built on kernel version 2.6.33.2...therefore it's pretty safe to assume that when you select a custom kernel, it needs to also be based on the 2.6.33.2 kernel. I think at least a couple of the custom kernels available now are just modified Cyanogen kernels.

Now, if you're running CM v5.0.6, there are a couple kernels popping up that take advantage of the VFPv3 optimizations instead of the previous NEON ones. In fact, I just flashed the Pershoot kernel with VFPv3 support on my phone yesterday... Honestly, I've tried a few and I think all of them are pretty similar, at least from what I can tell...