Wednesday, 8 December 2010

Thanks for the memory - Red Hat Enterprise Linux 5.5

For my Lotus Connections 3.0 environment, I'm using a VMware image of Red Hat Enterprise Linux 5.5, the 32-bit version, and noticed today, at a colleague's suggestion, that I only had 3.1 GB of memory available to me within the guest OS even though I'd allocated 4 GB to the VM itself.

Thinking it through, I realised that I was using a 32-bit kernel - 2.6.18-194.26.1.el5 - which doesn't, by default, support more than 3 GB.

Therefore, I had two choices: -
  • Switch to a 64-bit kernel and/or distribution, meaning that I'd potentially lose all of my installed code
  • Use the Physical Address Extension (PAE) kernel
Guess which option I took :-) Now I'm lucky enough to have an internal mirror of the Red Hat Network (RHN) available to me via my company, so I could simply install the kernel using YUM as follows: -  

yum install kernel-PAE                            ( note that PAE is capitalised )

Having done this, I needed to configure it to be my default kernel. Now RHEL uses GRUB, but there's no obvious GUI to manipulate the GRUB configuration files, and I wanted to be a wimp and avoid the need to manually hack them.

Tada ... to the rescue comes system-config-boot which is a graphical tool to allow one to manage the GRUB configuration.

I installed it in the same manner: -

yum install system-config-boot

and then ran the command; this allowed me to select the right kernel - 2.6.18-194.26.1.el5PAE - and then save the new configuration as default.

When I rebooted, I was able to see all 4 GB as available for use :-)

I note that RHEL 6 has deprecated system-config-boot - sadly with no replacement :-(

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