Support more than 4GB on 32 bit Linux

Please note you must have a PAE enabled machine for this operation to work. This PAE kernel supports memory up to 64GB. Physical Address Extension (PAE) is a feature, first implemented in the Intel Pentium Pro to allow x86 processors to access more than 4 gigabytes of random access memory (RAM).

A non-PAE kernel can only address up to 4GB of memory. Install the kernel-PAE package if your machine has more than 4GB of memory.

How to show current Kernel version

uname -r

How to Install PAE kernel?

To install PAE kernel, use the yum command:

# yum install kernel-PAE

Output:

Loading “installonlyn” plugin
Setting up Install Process
Setting up repositories
Reading repository metadata in from local files
Parsing package install arguments
Resolving Dependencies
–> Populating transaction set with selected packages. Please wait.
—> Downloading header for kernel-PAE to pack into transaction set.
kernel-PAE-2.6.18-8.1.15. 100% |=========================| 207 kB 00:00
—> Package kernel-PAE.i686 0:2.6.18-8.1.15.el5 set to be installed
–> Running transaction check

Dependencies Resolved

=============================================================================
Package Arch Version Repository Size
=============================================================================
Installing:
kernel-PAE i686 2.6.18-8.1.15.el5 updates 12 M

Transaction Summary
=============================================================================
Install 1 Package(s)
Update 0 Package(s)
Remove 0 Package(s)

Total download size: 12 M
Is this ok [y/N]: y
Downloading Packages:
(1/1): kernel-PAE-2.6.18- 100% |=========================| 12 MB 00:12
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
Installing: kernel-PAE ######################### [1/1]

Installed: kernel-PAE.i686 0:2.6.18-8.1.15.el5
Complete!

Reboot the server:

# reboot

That’s it all done

However, if your memory still isn’t showing up…

Still not showing up?

Make sure you have the new PAE kernel installed:

uname -r

It should read as:

2.6.18-8.1.15.el5PAE

The version number will change, but the extesnsion should show “PAE”

If it is still showing the old version of the Kernel then:

vi /boot/grub/grub.conf

Make sure the PAE kernel has first priority and then change the default line to 0:

default=0

Save the file

SHIFT ZZ

and reboot

# reboot

The new kernel should now show, test with:

uname -r

and lastly check the free memory with:

free -m

or

top

for activity.

Let us know how you get on with a comment below below.

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