The "Which Kernel to take"-decision

[Karl Voit]

Hi!

The subject is intended not to be "Tell me, whick kernel should I
take" followed by "Use the latest benh-kernel"! I am using linux a few
years and I feed qualified to decide, why this or that kernel should
be used.

In advance: Sorry for this long posting but I think that these
questions are not answered in "one piece" yet and I think that the
followups to this posting will clearify the situation for a lot of
people with the same questions like me. Please correct me, if I was
too dumb for google :-)

I have an 600MHz iBook2 and concerning the kernel modules I need, I am
using mostly FireWire (sbp2) and usb-modules for USB-sticks. These are
my absolute minimum requirements, that should work. External VGA would
be fine but I guess that ther will be no better result (blurred
picture, almost unusable) than the m3mirror of [1].

,----
| What did I use until now?
`----

I set up my iBook (with dualboot with OS 10.2) a few years ago by
myself using the benh-kernel (now: 2.4.23-pre5-ben0). I compiled it by
myself and added some modules here and there. No special kernel
patches except for a tryout of cryptoloop and connecting a Zaurus PDA
using usbnet and usbserial.

,----
| Why do I want to change my kernel?
`----

Several things are not working satisfying, lead by the firewire
subsystem. Unfortunately, I got kernel oops and sometimes, the modules
just hang (rmmod hangs and no firewire-device can be accessed any
more).

,----
| What are the options concerning kernel version?
`----

For the moment, kernel 2.4 and 2.6 are the options - in various
subversion numbers. I was using kernel 2.4 since now because 2.6 seems
to be quite "unstable" in certain things like firewire, usb and
stuff. And I was not sure, if there is a smooth (easy) way to change
from 2.4 to 2.6 without ending up with too much old crap on my system.

So: what kernel (2.4 or 2.6) do you recommend upon which arguments?

Is it easy to switch from 2.4 to 2.6?[3]

,----
| What are the options concerning kernel(-image) download-source?
`----

As far as I know, there are two options for getting the kernel: debian
repository and benh (using cvs or something).

The Debian way
==============

Since I am using Debian unstable PPC, the first attempt was an
"apt-cache search kernel|grep kernel-image". This results in several
kernels (for G3 and not-SMP):

kernel-image-2.4.27-power3-chrp
kernel-image-2.4.27-power3-pmac
kernel-image-2.4.27-power3-prep
kernel-image-2.4.27-powerpc-chrp
kernel-image-2.4.27-powerpc-pmac
kernel-image-2.4.27-powerpc-prep
kernel-image-2.4.27-powerpc-small-chrp
kernel-image-2.4.27-powerpc-small-pmac
kernel-image-2.4.27-powerpc-small-prep
kernel-image-2.6-power3
kernel-image-2.6-powerpc
kernel-image-2.6.8-power3
kernel-image-2.6.8-powerpc
kernel-image-2.6.9-power3
kernel-image-2.6.9-powerpc
kernel-image-power3
kernel-image-powerpc

Quite a long list. Quite some vocabulary, that should be clearified.

chrp: What are CHRP Power3 boxes?

prep: What are PReP based Power3 computers?

pmac: "This version contains the kernel image for yaboot using Power3
based boxes." This seems to be my machine.

small: What is missing in the small-version?

"apt-cache show" explains at least, that kernel-image-2.6-powerpc is
not ment for my G3 CPU. So the *-powerpc variants can be ignored by me
(IMHO). kernel-image-2.6-power3 seems to be only a "link" to the
current 2.6-kernel-package. Also kernel-image-power3.

pmac or power3 seems to be OK for my system, not only benh wrote on
his page[1], that "Kernels here are tuned for PowerMac machines but
should work on other PPC machines as well."

Based on these things, the list remaining would be:

kernel-image-2.4.27-power3-pmac
kernel-image-2.4.27-powerpc-pmac
kernel-image-2.4.27-powerpc-small-pmac
kernel-image-2.6.8-power3
kernel-image-2.6.9-power3

Assumed, that I want to use a debian kernel, what would be my choice
on which arguments? (stability, features, ...)

Are there all possible kernel modules built in?

Are there all major kernel patches built in?

The benh way
============

Benjamin Herrenschmidt seems to be _the_ Linux PPC geek here :-)

Good to have him and his work but I was always a little bit confused,
why his "perfectly"(?) kernel was not used in Debian (or is it?).

His PPC-page[1] is quite outdated ("Last revision of this page: Sept
20, 2001") and the second source I found was PPCKernel[2].

There, the "Choosing a Kernel" section did answer me some few
questions but not all. The resume there was "Official 2.6 PowerMac is
a great place to start!" but I do not know, if this one is as stable
as it seems to be. I heard of a lot of problems they still have with
2.6.

Assumed, that I want to use a benh/PPCKernel.org kernel, what would be
my choice on which arguments? (stability, features, ...)

Are there all possible kernel modules built in?

Are there all major kernel patches built in?

Choosing which way
==================

I'm very much in favour of the debian way, because of the simplicity
of an "apt-get install kernel-image..." and the correspondent updates
of it.

But if it should be the case, that the benh/PPCKernel.org kernel
offers much more advantages over the Debian kernels, I am willing to
try out BitKeeper for the first time :-)

,----
| Thank you!
`----

I hope you see my intentions and help me to clearify these open
questions. Depending on the answers here, I will probably publish the
results on my howto-section of my homepage[4] not at least because my
iBook PPC HowTo is rather outdated :-)

Thank you _very_ much for digging through this posting so far :-)


[1] http://penguinppc.org/~benh/

[2] http://www.ppckernel.org/

[3] I am thinking of my work spent in various hotplug-scripts,
PDA-sync-scripts, CD/DVD/burning, FireWire, USB-Sticks and so on.

[4] http://www.karl-voit.at/howtos/

[Jack Malmostoso]

Post by Karl Voit
"Use the latest benh-kernel"!

Which is actually what all boils down to :)

I haven't understood well but looks like you have a Debian box, so this
should make it much easier for you to try and test various kernel, even
homemade.

The power3 kernel-images should fit just right your machine, and the only
package required for switching 2.4-->2.6 is module-init-tools that will
take care of module loading differences between the two releases.

Anyway, I think you already know about make-kpkg, so it will be quite easy
for you to compile a kernel tailored for your iBook and if you have not
done so already, go at http://tuxmobil.org and see if there are others
with the same story as yours.

HTH

[Anton Ertl]

Post by Karl Voit
So: what kernel (2.4 or 2.6) do you recommend upon which arguments?

I use a stock 2.6.9 kernel with perfctr patch on my ibook with Debian
Sarge and it works.

Post by Karl Voit
Is it easy to switch from 2.4 to 2.6?[3]

Well, if your system is too ancient, you may have to update too much
software (modutils etc.). Should not be an issue for a Debian user, though.

Post by Karl Voit
[3] I am thinking of my work spent in various hotplug-scripts,
PDA-sync-scripts,

No experience.

Post by Karl Voit
CD/DVD/burning,

Minor changes.

Post by Karl Voit
FireWire,

No experience

Post by Karl Voit
USB-Sticks

No change.

Post by Karl Voit
and so on.

I have rarely experienced such problems from kernel changes.

Post by Karl Voit
,----
| What are the options concerning kernel(-image) download-source?
`----
As far as I know, there are two options for getting the kernel: debian
repository and benh (using cvs or something).

My primary source is kernel.org.

Post by Karl Voit
chrp: What are CHRP Power3 boxes?
prep: What are PReP based Power3 computers?

Power3 are now-obsolete IBM boxes. CHRP and PReP are standards for
designing PPC systems (also used by Apple).

Post by Karl Voit
I'm very much in favour of the debian way, because of the simplicity
of an "apt-get install kernel-image..." and the correspondent updates
of it.
But if it should be the case, that the benh/PPCKernel.org kernel
offers much more advantages over the Debian kernels, I am willing to
try out BitKeeper for the first time :-)

Why not try the Debian kernel, and if any of the features you want
don't work, you can still try another approach.

- anton

[Shyamal Prasad]

"Karl" == Karl Voit <***@Karl-Voit.at> writes:

Karl> Is it easy to switch from 2.4 to 2.6?[3]

Yes, on a Debian system (though I can only speak from having done it
on an x86 architecture). My powerpc system has only been booted with
2.6.8.

Karl> The Debian way ==============

Karl> Since I am using Debian unstable PPC, the first attempt was
Karl> an "apt-cache search kernel|grep kernel-image". This results
Karl> in several kernels (for G3 and not-SMP):

Karl> kernel-image-2.4.27-power3-chrp
Karl> [....removed....]
Karl> kernel-image-2.4.2

Karl> Quite a long list. Quite some vocabulary, that should be
Karl> clearified.


http://packages.debian.org/cgi-bin/search_packages.pl?version=all&subword=1&exact=&arch=any&releases=all&case=insensitive&keywords=kernel-image-2.6.8-power&searchon=names

click on each link and it will tell you what it is for.

Karl> Assumed, that I want to use a debian kernel, what would be
Karl> my choice on which arguments? (stability, features, ...)

Karl> Are there all possible kernel modules built in?

usually yes.

Karl> Are there all major kernel patches built in?

usually yes. You can download the kernel-patch-debian-2.6.8 package to
see what is included.


Karl> I'm very much in favour of the debian way, because of the
Karl> simplicity of an "apt-get install kernel-image..." and the
Karl> correspondent updates of it.

I'm not sure what is holding you from doing this (disclaimer: I hardly
have 3 weeks of experience running Linux on powerpc).

Karl> But if it should be the case, that the benh/PPCKernel.org
Karl> kernel offers much more advantages over the Debian kernels,
Karl> I am willing to try out BitKeeper for the first time :-)

If there is a feature that you think is essential that Debian support
in its 2.6.8 kernel why not file a bug?

Cheers!
Shyamal

[Derrik Pates]

Post by Karl Voit
The subject is intended not to be "Tell me, whick kernel should I
take" followed by "Use the latest benh-kernel"! I am using linux a few
years and I feed qualified to decide, why this or that kernel should
be used.

Ben has ceased maintaining a separate kernel tree, and now ships his
changes directly off to Linus & Co.

Post by Karl Voit
I have an 600MHz iBook2 and concerning the kernel modules I need, I am
using mostly FireWire (sbp2) and usb-modules for USB-sticks. These are
my absolute minimum requirements, that should work. External VGA would
be fine but I guess that ther will be no better result (blurred
picture, almost unusable) than the m3mirror of [1].

I'm currently using the 2.6.9-powerpc kernel image on my PowerBook Pismo
(G3 FireWire) running Debian; FireWire works find on it, as well as a
memory stick that I have (plug in, mount, use).

Post by Karl Voit
So: what kernel (2.4 or 2.6) do you recommend upon which arguments?
Is it easy to switch from 2.4 to 2.6?[3]

Yes. You need to install the relevant package, which will also install the
'module-init-tools' package, to allow you to load the relevant modules.
Make sure that yaboot is set up to load the kernel and initrd. I'd also
recommend installing the 'discover' package, if it isn't already.

Post by Karl Voit
As far as I know, there are two options for getting the kernel: debian
repository and benh (using cvs or something).

No longer; until recently I was using Linus' vanilla 2.6.x sources to
build my kernels, but I lately have been using the packaged kernels
instead.

Post by Karl Voit
chrp: What are CHRP Power3 boxes?
prep: What are PReP based Power3 computers?

Some systems are CHRP, some others are PReP. They are different PPC
reference hardware platforms.

Post by Karl Voit
pmac: "This version contains the kernel image for yaboot using Power3
based boxes." This seems to be my machine.

pmac would be anything put out by Apple, pretty much.

Post by Karl Voit
"apt-cache show" explains at least, that kernel-image-2.6-powerpc is
not ment for my G3 CPU. So the *-powerpc variants can be ignored by me
(IMHO). kernel-image-2.6-power3 seems to be only a "link" to the
current 2.6-kernel-package. Also kernel-image-power3.

Wrong, a G3 is not a Power3. Power3 is an IBM-only superset of the PowerPC
architecture; G3 is simply a PowerPC, so you should definitely use the
powerpc kernel, otherwise your system won't boot.

Post by Karl Voit
Assumed, that I want to use a debian kernel, what would be my choice
on which arguments? (stability, features, ...)

Well, I'd suggest the 2.6.9-powerpc kernel. That's what I'm using, with
good success (including power management functionality).

Post by Karl Voit
Are there all possible kernel modules built in?

The kernel package includes the relevant modules.

Post by Karl Voit
Are there all major kernel patches built in?

Some relevant kernel patches are incorporated, yes.

Post by Karl Voit
The benh way
============

As above, you would not be using a benh tree, as benh now submits his
changes directly for inclusion in the official tree. You could build
yourself a kernel based on the vanilla 2.6.9 tree, but anymore it's really
not worth it, or at least it's not in my estimation.