RHEL / CentOS Support 4GB or more RAM ( memory )
If you have 4 GB or more RAM use the Linux kernel compiled for PAE capable machines. Your machine may not show up total 4GB ram. All you have to do is install PAE kernel package.
This package includes a version of the Linux kernel with support for up to 64GB of high memory. It requires a CPU with Physical Address Extensions (PAE).
The 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 (>=4GB).
How Do I Install PAE kernel?
To install PAE kernel, use 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!
Just reboot the server and make sure you boot with PAE kernel i.e. 2.6.18-8.1.15.el5PAE:
# reboot
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Tags: CentOS 4GB support RAM, kernel package, linux kernel, linux large memory support, RHEL 4GB RAM support, yum_command ~ Last updated on: November 10, 2007



Wanted to info regarding this since Im interested in a custom configured dell notebook with a total of 4GB RAM (2×2GB) with the intention of installing Fedora 8 or Ubuntu 7.10 but was wondering if Linux can ’see’ 4GB of RAM unlike Windows which utilizes a max of ~3GB of RAM ?
Anjanesh,
Just install kernel-PAE under Fedora 8 and you should able to use 4 GB - 64 GB RAM out of box
I’m not windows expert, but it does support 64GB or more RAM if you use 64 bit Windows Vista / 2003 Server. Keep in mind that 64 bit windows has huge software / hardware compatibility issues.
HTH
kenel-PAE isn’t available in CentOS 3/ RHEL 3 or CentOS 4/ RHEL 4 (at least, not on my systems). Instead, install and boot kernel-hugemem.
Dimitri,
Yup, kernel-PAE is CentOS 5/ RHEL 5 / Fedora 8 only.
Hi all.
I am planning to buy a Dell workstation with RHEL 5 with 4 Gb ram.
If I had to install RHEL 3, for old CFD softwares, would i have problems in seeing the total ram ?
Thanks all and regards
Herger
FYI, this is only for 32bit versions of RHEL/Centos… The 64bit versions don’t supply, nor do they need these extensions
I have a Red Hat 8, 64-Bit installation and the BIOS sees 4Gb of RAM, but Fedora only sees 3.1. It is an HP computer and the BIOS is very limited as far as configurable options. Why won’t Fedora see all the RAM?
my PC Bios only reports 3.2GB memory available. Does linux has its own basic IO support? Or it use standard bios support for IO?
Thanks.
older Intel chipsets (pre-965, including 945) do not support memory remapping - thus limiting access to the memory being overlapped by IO space.