3

I recently encountered an issue where I had installed a 32-bit RHEL 6 server on a system with a 64-bit processor. I did some research and found that RHEL 6.0 has PAE enabled on 32-bit machines, which allows the user to use up to 64 GB of RAM in a 32-bit OS.

However, RHEL 6 server 32-bit with PAE still has the limitation that a single process can only have a maximum address space of up to 4 GB. These details could be seen from here and here.

So, I wish to upgrade my 32-bit installation of RHEL 6 server to a 64-bit installation. How could I do it without losing any of the data that is already present on the 32-bit machine?

  • I think the process limit of a 32 bit process, and 32bit kernel (pae or other wise), is 3GB. 1GB is reserved by kernel for its own use. I upgraded my kernel to 64bit, now 32bit apps can use full 4GB. I just installed new kernel and told grub to use it. ( I am using debian ). – ctrl-alt-delor Jul 16 '14 at 17:59
3

First things first.

I had setup my 32 bit system as below.

/boot - /dev/sda1
/     - /dev/sda2
swap  - /dev/sda3
/home - /dev/sda4

If you have not setup the /home in a different partition, then you have to backup all the data and restore it. You cannot do as described in this answer.

/home is in different partition

So if you have /home in different partition, you can do the below steps.

  • Insert the RHEL 6.0 64 bit DVD into the drive or use an USB disk that has the image of 64 bit OS.
  • We will get the options to do a fresh installation or upgrade to another RHEL version.
  • If we select Upgrade option, it will fail with an exception because upgrading directly from 32 bit to 64 bit is not possible. Even before trying, Redhat gives a clear message saying that the process won't succeed.
  • Select the fresh installation option. Now, do the following.

    /dev/sda1 - Select the checkbox for formatting the bootloader 
                and change the mount point as /boot. 
    /dev/sda2 - Select the checkbox for formatting the / directory 
                and change the mount point to /.
    swap      - do nothing. 
    /dev/sda4 - Select the mount point as /home and do not do anything else.
    
  • Proceed with the installation process as you normally do and we can have a 64 bit RHEL without affecting any of the user data.

  • On debian you can first install 64bit kernel, then install 64bit libs, then install some 64 bit application. (I have only done the first). – ctrl-alt-delor Jul 16 '14 at 18:01

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.