由于VM增加的内存不显示，需要更新HEADER才能讀出超過4G的部份。
1.更新kernel-PAE、kernel-PAE-devel、kernel-headers
yum -y update
yum -y install kernel-PAE
yum -y install kernel-PAE-devel
yum -y install kernel-headers
2.修改/boot/grub/grub.conf直接用winscp上去或者用vi修改/boot/grub/grub.conf，
先查看下内核版本
[root@ ~]# uname -a
Linux zz-vmgamesv01 2.6.18-238.19.1.el5PAE #1 SMP Fri Jul 15 08:15:44 EDT 2011 i686 i686 i386 GNU/Linux
cat /boot/grub/grub.conf
# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE: You have a /boot partition. This means that
# all kernel and initrd paths are relative to /boot/, eg.
# root (hd0,0)
# kernel /vmlinuz-version ro root=/dev/VolGroup00/LogVol00
# initrd /initrd-version.img
#boot=/dev/sda
default=1
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title CentOS (2.6.18-238.19.1.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-238.19.1.el5 ro root=/dev/VolGroup00/LogVol00
initrd /initrd-2.6.18-238.19.1.el5.img
title CentOS (2.6.18-238.19.1.el5PAE)
root (hd0,0)
kernel /vmlinuz-2.6.18-238.19.1.el5PAE ro root=/dev/VolGroup00/LogVol00
initrd /initrd-2.6.18-238.19.1.el5PAE.img
title CentOS (2.6.18-164.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-164.el5 ro root=/dev/VolGroup00/LogVol00
initrd /initrd-2.6.18-164.el5.img
当选择title CentOS (2.6.18-238.19.1.el5) ,default=0 ,
选择title CentOS (2.6.18-238.19.1.el5PAE) default=1,
选择title CentOS (2.6.18-164.el5),default=2
因为内核版本是2.6.18-238.19.1.el5PAE ，所以选择修改default=1,
这个看实际位置在哪里而作选择
3.重启系统 init 6
应VM增加的内存而正常显示出来了
[root@~]# free -m
total used free shared buffers cached
Mem: 7923 4773 3150 0 169 3074
-/+ buffers/cache: 1529 6394
Swap: 3039 0 3039
本文转自 holy2009 51CTO博客，原文链接:http://blog.51cto.com/holy2010/629815
