Install Centos 6 on a Non-PAE Machine

I have a Thecus N5200 that was modified to have a VGA port. Though the machine will run a variety of current Linux distributions, I wanted it to run Centos 6. Unfortunately, the N5200 doesn’t support PAE, which Centos 6 requires.

The first major problem is that a Non-PAE machine won’t even boot the Centos installer CD/DVD. You have to find some way around that. There are several ways to get around that but they are all quite complex and time-consuming. Plus, as time goes on they work less and less. The old software needed is harder and harder to find. I instead chose to simply install Stella. It’s a Desktop focused Linux distribution that is based on Centos 6 and the 32bit version includes a Non-PAE kernel. If you’re looking to install a Centos 6 desktop, install Stella and you’re all set. It’s great. The developer did a great job keeping things compatible with Centos 6 while also adding in things like video codecs and the like.

For my little project with the N5200 though I wanted to go a little further. I wanted to install Stella, to get around the NON-PAE requirement, and then convert it back to a standard Centos 6 installation… or close to it.

I booted the Stella DVD and installed it to disk. Once I booted into it from my hard drive I set about searching for and removing packages not part of the normal Centos install.

The first thing I did was search for installed packages from repos outside of a normal Centos installation. I used this command initially

yum list installed

to get a look at everything installed and where it was installed from. From there I started to use grep as well to filter things down.

yum list installed|grep dex

Many of the packages were from a repo that included the word ‘dextop’ so I filtered the list to show me those by piping the output to ‘grep dex’.

With a list packages, I use the ‘yum remove’ command to remove them:

yum remove a52dec amrwb b43-firmware bluecurve-metacity-theme faac ffmpeg-libs gnome-web-photo goocanvas faad2-libs gstreamer-plugins-bad gtkimageview lame-libs libdca libdvdcss libfribidi libmad libmimic libmms libmpeg2 libsidplay mjpegtools-libs nux-dextop-release opencore-amr opencore-amr perl-Gnome2-Canvas perl-Gnome2-VFS perl-Gnome2-Wnck perl-Gtk2-Unique perl-Proc-Simple perl-X11-Protocol-Other twolame-libs unrar flash-plugin xulrunner19 xvidcore

(If you copy that command, be sure to remove any line breaks you browser may have put in.)

From there I used the yum list command again to search for ‘stella’. It turned up a package called ‘stella-release’. The _____-release package is used to tell the system what the version and name of the OS is. If you remove it, as I did, it will take with it a lot of packages.

yum remove stella-release

Now.. don’t reboot!

The next step is to install a new _____-release package. In this case, I needed to install the Centos 6.6 release package, which I was able to find in the Centos mirrors. Just find the package and use yum to install it. The file location/name may change slightly overtime but I used this command:

yum install http://mirror.centos.org/centos-6/6.6/os/i386/Packages/centos-release-6-6.el6.centos.12.2.i686.rpm

If yum complains and won’t run, download the packaged and install using the rpm command:

wget http://mirror.centos.org/centos-6/6.6/os/i386/Packages/centos-release-6-6.el6.centos.12.2.i686.rpm && rpm -i centos-release-6-6.el6.centos.12.2.i686.rpm

I then also installed the epel package, which I almost always use with Centos. (Again, the link could be slightly changed for you)

yum install http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm

From here, you need to start rebuilding the OS. Some of the work we’ve done will have broken the system so before a reboot we need to replace many of those packages with official Centos packages or, in most cases, the same packages we just removed but without the stella-release package requirement.

I wanted to make sure I kept the Gnome 2 GUI so I used the yum groupinstall command to rebuild most of those packages.

yum groupinstall "Desktop" "Desktop Platform" "X Window System" "Fonts" "Internet Browser"

From here on the system is basically a clean Centos 6 install but with Stella branding and their non-PAE kernel. The kernel I want to keep but if possible, I’d like to remove the branding. This one can be a bit messy. If you try to pull branding you basically uninstall the whole OS.

You have to remove the branding information without checking for dependence, as yum would, and then replace those stella packages with the regular Centos ones.

Firstly, remove the stella branding:

rpm -e --nodeps stella-logos && rpm -e --nodeps stella-bookmarks && rpm -e --nodeps stella-indexhtml

Next, add back in the Centos versions of those packages:

yum install redhat-logos centos-indexhtml redhat-bookmarks

Yum will complain that the rpmdb has been edited and there are missing packages, etc.. But, we know that already and running that command will fix the problems.

Following that, it’s probably a good idea to run a ‘yum check’ command to be sure everything is resolved. It will take a look at your yumdb and let you know if it sees any problems with unresolved dependencies, etc.. It took forever to run on my N5200 but it all came back clear.

If, like me, you’ve gone this route to get around the PAE issue in Centos you’re going to want to update your yum.conf file to tell the system not to install any kernel updates. Any kernel you get from Centos will not work on your machine.

vi /etc/yum.conf

Just find a spot under the [main] header and add the line:

exclude=kernel*

This will just exclude kernel updates. It’s not ideal for security but, at least for me, it’s worth it to have a working Centos 6 system.

Now, we’re very close. Openssh-server has been removed and I wanted it back so I reinstalled it and set it to run on boot.

yum install openssh-server && chkconfig --add sshd

Next, if you want to boot into the GUI, instead of to the terminal, the inittab file needs to be updated.

vi /etc/inittab

The final line says ‘id:3:initdefault:’ but to boot to a gui it needs to be ‘id:5:initdefault:’ instead. Update that 3 to a 5 and save the file.

The very final detail would be to look around for unneeded but still installed packages. You can do a quick search for unneeded libraries:

package-cleanup --leaves

And then uninstall those rpms, which serve no purpose.

I’m sure there are other remnants of Stella lurking around the system but these steps cleaned up my install and brought it back to a pretty good state. I’m happy with it and it’s been very stable.

Sure, I could have just kept the normal Stella install but where’s the fun in that?