HowTo Ubuntu 32 bit with 4Gb

[phico]

Hi,

I have a macbook pro with 4Gb RAM.

It was quite simple to make it a pure linux machine as this http://ubuntuforums.org/showthread.php?t=198453

But .. I really wanted to use those 4Gb because I plan to run some virtual machines ...

The solution was to use a 64 bit system .. but .. soon I noticed that
I was 'downgrading' quite everything from 64 to 32 bit because of incompatibilty problems ...

So I looked a little bit more about 32 bit solutions with PAE
(Physical Address Extension)

In a linux kernel it is just a kernel config parameter : CONFIG_HIGHMEM64G

In Ubuntu Desktop kernel it has not been set by default, in Ubuntu Server kernel it has
been set .. but Ubuntu Server kernel is optimized for a Server not for a desktop environement
(no preemption, timer interrupt of 100Hz against 250Hz for the desktop ... )

So the solution was to recompile the kernel.

The problem is my config (as many other) relies on some restricted-modules. There are some information on
the ubuntu wiki about how to recompile those restrited modules for a custom kernel but it is quite a hack of
config files .. not so straightforward.

To keep it simple, I just created a new kernel with same name (abi,flavour..) and so
recompile the restricted module with default config files .. and that's it !


Here it is :

create a work directory

sudo apt-get install linux-kernel-devel fakeroot build-essential

sudo apt-get build-dep linux-image-$(uname -r)
apt-get source linux-image-$(uname -r)

sudo apt-get build-dep linux-ubuntu-modules-$(uname -r)
apt-get source linux-ubuntu-modules-$(uname -r)

sudo apt-get build-dep linux-restricted-modules-common
apt-get source linux-restricted-modules-common

go to linux-xxxx

and edit debian/config/i386/config.generic

(adapt the path to your platform and flavour)

change the folowing lines :

# CONFIG_HIGHMEM4G=y
CONFIG_HIGHMEM64G=y

Now compile kernel and modules

go to linux-xxx

CONCURRENCY_LEVEL=2 AUTOBUILD=1 NOEXTRAS=1 fakeroot debian/rules binary-debs flavours=generic

go to linux-ubuntu-modules-xxx/

CONCURRENCY_LEVEL=2 AUTOBUILD=1 fakeroot debian/rules binary-debs flavours=generic

go to linux-restricted-modules-xxx

CONCURRENCY_LEVEL=2 AUTOBUILD=1 fakeroot debian/rules binary-indep binary-arch

Now install all packages :

go to the root of your working directory

sudo dpkg -i linux-image-xxx-generic_2.6.24-19.34_i386.deb
sudo dpkg -i linux-headers-xxx-generic_2.6.24-19.34_i386.deb
sudo dpkg -i linux-ubuntu-modules-xxx-generic_xxx_i386.deb
sudo dpkg -i linux-headers-lum-xxx-generic_xxx_i386.deb
   
sudo dpkg -i linux-restricted-modules-xxx-generic_2.6.24.13-19.44_i386.deb 
sudo dpkg -i nvidia-glx-new_169.12+xxx_i386.deb

(this is for macbook pro 4. Your platform might have other restricted package to be installed)

Reboot and DO NOT udate your kernel and modules with ubuntu repo's because you will go back to the beginning !

Hope this help you to use your 4 Gigs !

Screnshot in attachment ..

[Sef]

Moved to Tips and Tutorials.

[phico]

Thanks, it's better here indeed !

[Klaue]

Thank you phico. I was planning to buy two additional GBs and wondered if I could use them without a 64bit system
Is there a flag one could set to prevent automatic kernel updates without having to check all the updates every time?

And (this may sound dumb, because I have no expertise at all with 64bit systems) does all 32bit software still work on a 64Bit-system (while only using 4 GB of ram even if you have way more) or doesn't it? I mean, was your reason for it that you still used 32bit software or what do you mean with "downgrading"?

[TheAL76]

I just use the server kernel. I can use all of my 4 GB of RAM.

[phico]

I just use the server kernel. I can use all of my 4 GB of RAM.

This is simpler to setup but I would not advice this because ...
there are other differences between Desktop and Server kernel.
And of course Server kernel is not optimized for a Desktop.

For example there is no preemption in server kernel.
The server timer frequency is set to a 100 HZ while the desktop is set to 250 HZ ..

http://www.ubuntu.com/products/whati...eatures/kernel

So I prefer to recompile the Desktop kernel with the only PAE flag
to get a Desktop optimized kernel with 4Gb up to 64Gb support ..

[phico]

Is there a flag one could set to prevent automatic kernel updates without having to check all the updates every time?

I try to find the same .. but no way until now. I just uncheck
module, kernel and header at each update with update manager

does all 32bit software still work on a 64Bit-system (while only using 4 GB of ram even if you have way more) or doesn't it? I mean, was your reason for it that you still used 32bit software or what do you mean with "downgrading"?

Some (most of actually) 32 bit applications can work on 64 bit os
if you install some additional libs. Now it is not straightforward
and you have most of the time some additional hack to do ..

For example getting java and flash plugin working on firefox 64 bit
is a nightmare (no Sun Java plugin, Flash working not all the time...)
Then you can try to install firefox 32 with some hack to get it
working on 64 bit os ... and so and so .... I also get java
libraries not working on java 64 bits (even some sun sdk ...)

In the result it was more a battle to get 32 bit applications working
on 64 bit ! So I decided to go back to 32 bit + PAE because I get
4Gb support + all compatibilty. But the day java 64 is more used
and all firefox plugin are available in 64 bit .. I definitely go
for 64 bit

[kkfok1]

Just an alert to those having T61 or similar hardware. After following the instruction, the kernel can discover upto 4GB RAM but the volume, wireless, webcam (nvcvideo) all become not working.

I think Ubuntu team should enhance the current version or provide a non-compile way to discover upto 4GB.

Anyway, thanks for the post as I do learn the way to compile a new kernel.

[kud0gfx]

thanks very much for this!

[amp711]

Thanks for that info kkfok1. I almost pulled the trigger on a recompile this morning of my R61i and have decided against it.

I wish that it was just enabled by default. Don't really want to go through the hassle of switching to 64 bit...