Thread: Knoppix 7.0.1-EN DVD notes & comments

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A clarification from Klaus K (via private e-mail):

Hello (utu),

On Wed, Jun 06, 2012 at 05:09:25PM -0700, (utu) wrote:
> Greetings again, Klaus.
>
> I have a 64-bit computer with 4G b ram; a little of that stolen for graphics.
> I'm using Knoppix 7.0.2 and I don't recall having a 32-bit or 64-bit choice on that.
>
> If I use the cheatcode knoppix64, for uname -s I get linux, not linux64.

The name of the kernel is always "Linux", regardless of the file name it
was started with. In fact, the OS does not even know the kernels file
name, because it's the boot loader who loads it before there is
an OS running. You may find more useful information when looking at

cat /proc/cmdline

about how Linux was started than by looking at uname -a.

> I've seen a report of someone with 64-bits and 15 Gb with this same result.
> Neither of us seem to be able to turn on a 64-bit kernel in 7.0.2.

It's easy: If your system boots with "knoppix64" and starts properly,
it's running on the 64bit kernel on a 64bit CPU. On a 32bit CPU, the
64bit kernel will halt immediately after loading the kernel.

Comparison between uname -a in both cases:

knoppix:
Linux Microknoppix 3.3.7 #38 SMP PREEMPT Tue May 22 06:21:01 CEST 2012 i686 GNU/Linux

knoppix64:
Linux Microknoppix 3.3.7-64 #40 SMP PREEMPT Tue May 22 08:47:38 CEST 2012 x86_64 GNU/Linux

It's the "x86_64" architecture which shows the difference. The
"3.3.7-64" is only the kernel version number.

(I think) it's nice that the system behaves exactly the same when
running in 32 vs. 64bit mode, and you won't even notice much of a
difference in your daily work. Since the application layer uses 32bit
consistently, you don't have to care about finding a 64bit version of
proprietary plugins and libs if you need them.

> I took your (English) description to say I should expect this with ONLY 4 Gb;
> I understand this is a translation problem and not a (or an intended) fact.

So, my original statement reads correct, that you can use over 4GB of
RAM only when using the knoppix64 boot option, and not that the
knoppix64 boot option would require over 4GB of RAM. Yes?

> So I guess we have only one complaint not two. Is there a 64-bit iso out there?

If you are looking for a Knoppix version that uses a 64bit userspace
(i.e. ALL packages, applications and libs are compiled in 64bit mode),
there is none. So far, I don't see a big advantage in providing another
set of DVDs and CDs for a 64bit userspace which does not have a
significant improvement in either performance, usability or any other
justification for the extra effort and space consumption.

> Or are there some other preliminaries necessary to having a 64-bit kernel and
> all its trimmings? I see lots of headers and Makefiles with 64s in their names.

The reason for me to provide the 64bit kernel is not to have a complete
second OS installed with 64bit apps, but to allow systems with more than
4GB of RAM installed to work properly, and to use Knoppix also as rescue
system for 64bit installations which require a 64bit CPU and kernel to
run a chroot into them.

Maybe this table displays my intention more clearly:

| 64bit Apps/Libs | 32bit Apps/Libs |
--------------+---------------------+-----------------+
64bit CPU + | works | works |
64bit Kernel | | |
--------------+---------------------+-----------------+
32bit CPU + | doesn't | works |
32bit Kernel | work | |
--------------+---------------------+-----------------+
64bit CPU + | doesn't | works |
32bit Kernel | work | |
--------------+---------------------+-----------------+
32bit CPU + | not starting |
64bit Kernel | |
--------------+---------------------+-----------------+

So, the best compatibility is reached if I provide the 32bit
kernel and 32bit userspace by default (which always
works), and a 64bit kernel with the same 32bit userspace
as option (which works on 64bit CPUs only and allows
more than 6GB of RAM). Adding a 64bit userspace would
double, almost triple the needed space, or require a second
DVD.

Regards
-Klaus

Postscript from utu:
This may also explain why using knoppix64/linux64 as a 'DEFAULT' parameter
in syslinux.cfg causes a crash.