How to get 4gb of ram working in Ubuntu 32bit version... edited, be sure you read the end of the article
Recently I decided to upgrade the RAM memory of my Laptop to 4 GB. I was running my Ubuntu Jaunty 32 bit version with only 2 GB and it was clear that is was not enough to run my virtual machines in it.
I decided to buy 4 GB and install the memory, the installation went fine and the 4 GB of ram got detected properly in my BIOS settings. After checking my Ubuntu System Monitor and also by running in the terminal the "$ free" command, I realized that my 9.04 Desktop version was only showing me 3 GB of ram.... after googling I found that it was a limitation of 32 bit systems.
$ free
total used free shared buffers cached
Mem: 4053920 1133536 2920384 0 99908 428480
-/+ buffers/cache: 605148 3448772
Swap: 2208896 0 2208896
The solution:
A simple line that installs the server kernel in the Desktop version. This way, even though I'm running the 32bit desktop version, the kernel is actually the 9.04 server version.
Works fine ;) and I'm getting 4 GB of ram. To achieve this here are the commands:
sudo apt-get update
sudo sudo apt-get install linux-headers-server linux-image-server linux-server
SOLVED WITH 9.10 KARMIC KOALA
Using the Update Manager I had the opportunity of upgrading from 9.04 to 9.10... even thought I was using server kernel the update went without problems and the new 9.10 32bit kernel comes with PAE support. Because I wanted to replace my hard Drive (160gb / 5400rpm) with a (500gb / 7200 rpm) I decided to backup my home folder (40gb) and make a fresh, clean 64bit install. So right now I'm running Ubuntu 9.10/64 Karmic Koala in my beautiful 
laptop with 4gb ram and a 500gb / 7200 rpm hard drive.
- Comments
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|99.244.11.xxx |2009-09-28 22:41:19 Captain Canuck - Backwards Compatible with 32bit softwareFor instance, are you able to run firefox?
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|67.204.36.xxx |2009-09-28 23:58:58 Dan - Works because has PAE enabledThe reason why the 32bit Server kernel works with all 4GB of ram is because it has Phisical Extencion Address Enabled or PAE for short.
most applications on the Linux Real should be able to take advange of this, but some other dont and will only be able to use up to 3GB.
more info:
http://en.wikipedia.org/wiki/Physical_Address_Extension
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|98.206.238.xxx |2009-09-29 02:47:07 Erik - Server Edition supports PAEThe Server Edition kernel supports PAE, check the wiki page I linked to for more information.
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|194.7.137.xxx |2009-09-29 08:28:57 Olivier - Why no PAE in desktop kernels?If the Linux kernel in general supports PAE, why is it not enabled by default? OK, servers often have more RAM than the average desktop, but what with the beefier desktop machines?
I also have Ubuntu 9.04 running on a 4GB machine with only 3GB used. But I do not feel much for both options proposed here: installing a server kernel for a desktop (there must be a reason there is a seperate kernel voor servers, no?) or recompiling a kernel (a little too far fetched to get the extra GB addressed and I lack the technical knowledge to jump into that).
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There is a reason for not enabling the server kernel. Server kernel is configured with 100 Hz timer frequency and for a desktop this may not be sufficient. So Ubuntu comes with 250 Hz kernel which is a generic kernel. If you want more responsiveness, you can go with 1000 Hz kernel (in Ubuntu this is called rt kernel) Some of my thoughts on kernel frequency as I understood from kernelnewbies is written here http://duopetalflower.blogspot.com/2009/06/running-laptop-long-time-wi thout-it.html
Well, Ubuntu karmic has new PAE enabled kernel which will be having 250 Hz like generic kernel and should support all 4 GB systems out of the box. http://duopetalflower.blogspot.com/2009/09/upcoming-ubuntu-karmic-has- 32-bit-pae.html
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|40.0.40.xxx |2009-09-29 12:59:12 Terry - Server kernel not best solution for desktops/laptoMost people might not want to be using the server version of the kernel. You might want to run the 64 bit version of Ubuntu since it shows above you have a Core 2 Duo CPU. This would be a better way to address >3GB of RAM. I was reluctant to run the Ubuntu 64 on my laptop due to concerns that it would be slower or have software compatibility issues. Do not be concerned about this. Once I tried it, it work great. A tiny little bit more work to get 64 bit versions of Flash and Google Chrome, but not much.
Why do you think Ubuntu provides "desktop" and "server" versions of the kernel? Because they are optimized for the task.
Server versions will typically be more stable, sometimes at the expense of performance and compatibility with various hardware (i.e. graphics, etc.). The desktop version will likely provide better user interface response and better handle the latest 3d drivers and other "desktop" hardware. Also, keep in mind that PAE is using a ...
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|194.7.137.xxx |2009-09-30 08:25:20 Olivier - Server kernel not best solution for desktops/laptoMy question was rhetorical. However, your post makes me consider to switch to the 64bit distro because the only reason why I was holding off was indeed software support. But I am not using anything that is not coming from the stable repository so I should not bump into too much troubles. Got some pretty default hardware too.
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|76.179.252.xxx |2009-09-29 13:23:29 Rick - Compile your own worksI have held off going to 64 bit Ubuntu because I have few apps that do not work with 64 bit yet. I knew that I could use the server kernel, but I also was aware that the server kernel was not optimized for desktop use.
When the new Kernelcheck came out this summer I tried it and very easily had a desktop kernel that used the same configuration as my regular ubuntu desktop kernel except PAE was enabled and all my memory was available. Unfortunately, Kernel.org changed their website and kernelcheck no longer works. I tried to compile manually when 2.6.31 came out but had no success. It would be nice if someone who was good at compiling kernels would provide a PAE enabled version of the stock kernel for those of us with more than 3gb 32bit systems. I guess there is not that much demand anymore with everyone switching to 64bit.
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|40.0.40.xxx |2009-09-29 14:19:09 Terry - Probably not best solution - use 64 bit insteadMost people might not want to be using the server version of the kernel. You might want to run the 64 bit version of Ubuntu since it shows above you have a Core 2 Duo CPU. This would be a better way to address >3GB of RAM. I was reluctant to run the Ubuntu 64 on my laptop due to concerns that it would be slower or have software compatibility issues. Do not be concerned about this. Once I tried it, it work great. A tiny little bit more work to get 64 bit versions of Flash and Google Chrome, but not much.
Why do you think Ubuntu provides "desktop" and "server" versions of the kernel? Because they are optimized for the task.
Server versions will typically be more stable, sometimes at the expense of performance and compatibility with various hardware (i.e. graphics, etc.). The desktop version will likely provide better user interface response and better handle the latest 3d drivers and other "desktop" hardware. Also, keep in mind that PAE is using a ...
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Nice to see all the debate created by this article. To begin with, don't want to force anyone this solution.
This was what seem right for me, it's working stable, took 2 minutes to implement.
Sure, maybe the 64bit desktop version would be more recommended, each kernel for each purpose... but was afraid to test it due to software compatibility in 64 bit mode and also did not want a full time consuming reinstall.
About PAE kernel... fiddle with the kernel, lol... maybe next time. In the above posts, it would be nice to read some links and how-to in order to achieve that, and how easy or hard it is
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|151.188.18.xxx |2009-09-29 22:50:45 Terrell Prude' Jr. - How to make Server Kernel feel "faster" on desktThere are a couple of sysctl settings that will help speed up the responsiveness of a server kernel. I've tried this on RHEL/CentOS 4 and 5, both of which use a server-optimized kernel, and it works well. The speedup in K12LTSP deployments is definitely noticeable. It has to do with the kernel's "swappiness" behaviour.
sysctl -w vm.swappiness=1
sysctl -w vm.vfs_cache_pressure=50
The closer vm.vfs_cache_pressure is to 1, the better (to a degree) desktop response is. Careful, though. As the article I originally got this tip from says, "Values close to 100 provide no gain. Values close to zero can cause huge swap activity during big filesystem scans."
Thanks to Rudd-O for this helpful tip.
--TP
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|192.168.1.xxx |2009-09-30 15:55:40 DJ - This is not such a bad article...That article isn't so bad you make it to be. Those downsides are negligible.
I have used 32-bit kernels + PAE a long time and if you were sitting in front of one of those installations you'd be hard-pressed to identify the one with the 32-bit+PAE kernel without looking at "uname -a".
There are perfectly valid reasons why one _HAS TO_ use 32-bit + PAE.
In my case it was a commercial + closed source application by SUN that only existed as 32-bit binary on Linux and refused to run on 64-bit (the only 64-bit versions they produced was for Solaris 10). So I had the choice: Either run 32-bit Linux and not be able to use the full 8 GB RAM in my system or run Solaris 10 and not be able to use half the hardware and live with a totally outdated desktop ...
Going for a 32-bit Linux kernel with PAE solved that. I got a modern desktop with all the latest packages and I got to use all of my RAM.
Yes, there are theoretical downsides to using PAE like a theoretical performance impact betwee...
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