Building which kernel?

Building which kernel?

[John Whitmore]

I've a question regarding the building of the linux kernel, more specifically
which kernel to build. 

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.

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?

I've read various documentation on building the linux kernel but that's never
really mentioned, mainly I guess as you're building for the x86 Arch. But even
there can you jump major versions of kernel without effecting other installed
SW in the system?

John

Building which kernel?

[Lucas Tanure]

On Sun, Jun 14, 2015 at 10:11 AM, John Whitmore <arigead@gmail.com> wrote:

> I've a question regarding the building of the linux kernel, more
> specifically
> which kernel to build.
>
> 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.
>

Did you read the
https://www.raspberrypi.org/documentation/linux/kernel/building.md  ?
There is a few tags : https://github.com/raspberrypi/linux/releases


> 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?
>

The problem is not the user space programs, it's really if the newer kernel
will boot in your hardware.
If you use the RPi kernel, you can use the lasted kernel without problems,
but if you use the mainline kernel (Linus) you will have a few problems.
Just because it doesn't have all the modifications made on RPi kernel.


> I've read various documentation on building the linux kernel but that's
> never
> really mentioned, mainly I guess as you're building for the x86 Arch. But
> even
> there can you jump major versions of kernel without effecting other
> installed
> SW in the system?
>
If you read this docs you are able to test different kernel versions
without problems. So go test it.
More info at : http://elinux.org/Raspberry_Pi_Kernel_Compilation



>
> John
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies


Good luck

--
Lucas Tanure
+55 (19) 988176559
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Building which kernel?

[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

Building which kernel?

[John Whitmore]

On Sun, Jun 14, 2015 at 08:27:03AM -0700, Greg KH wrote:
> 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


Yes that clears up versions, thanks a milion.

John