Building which kernel?

[greg@kroah.com (Greg KH)]

On Sun, Jun 14, 2015 at 02:11:33PM +0100, John Whitmore wrote:
> I've a question regarding the building of the linux kernel, more specifically
> which kernel to build. 

Always the latest version, why would you want to build an old one?

> I've previously built the kernel for an 86 arch but this time I want to build
> for the RaspberryPi. I can easily get the current version of the installed
> kernel with the "uname -a"  command but that doesn't tell me the git repo
> where the kernel originated. I'd imagine that it's from the RPi git repo, but
> that adds another level of confusion as that git repo doesn't have any tags at
> all. So even given the version number from uname how to check out a suitable
> version of the kernel.

If you are using hardware that is not completly supported in the main
kernel.org repo, like many embedded devices like the RPi, I suggest
using the source repo that the project provides instead.

> I could take the latest from the RPi repo and use "make oldconfig" but I
> wonder how far, in kernel versions, I can jump and not affect the installed
> libs and utilities which have been built against another version of the
> kernel?

You should always be able to use a new kernel on old userspace with no
problems.  Going backwards is not supported (old kernel on new
userspace.)

hope this helps,

greg k-h