32位centos更换内核支持3G上以内存

32位centos 安装过程会查看内存大小。如果大于3.2G，系统自动安装PAE的内核，如果小于3.2G，系统安装不带PAE的内核，
最近升级一台服务器内存，2G增加到8G，系统在默认安装时安装了不带PAE内存，系统只能识别到3.2G内存，下面就是更换内核的方法，很容易哈


1，查看系统启动加载的内核
[root@tgds ~]# more  /etc/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/sda2
#          initrd /initrd-version.img
#boot=/dev/sda
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title CentOS (2.6.18-164.el5)
        root (hd0,0)
        kernel /vmlinuz-2.6.18-164.el5 ro root=LABEL=/ rhgb quiet
        initrd /initrd-2.6.18-164.el5.img




2，查看BOOT目录中的内核文件
[root@tgds ~]# ll /boot/
总计 5591
-rw-r--r-- 1 root root   68663 2009-09-03 config-2.6.18-164.el5
drwxr-xr-x 2 root root    1024 2011-10-23 grub
-rw------- 1 root root 2605511 2011-04-01 initrd-2.6.18-164.el5.img
drwx------ 2 root root   12288 2011-04-01 lost+found
-rw-r--r-- 1 root root   80032 2009-03-13 message
-rw-r--r-- 1 root root  107405 2009-09-03 symvers-2.6.18-164.el5.gz
-rw-r--r-- 1 root root  954947 2009-09-03 System.map-2.6.18-164.el5
-rw-r--r-- 1 root root 1855924 2009-09-03 vmlinuz-2.6.18-164.el5






3，系统光盘中找到内核文件，上传服务器并安装
[root@tgds ~]# rpm -ivh kernel-PAE-2.6.18-164.el5.i686.rpm 
warning: kernel-PAE-2.6.18-164.el5.i686.rpm: Header V3 DSA signature: NOKEY, key ID e8562897




Preparing...                ########################################### [100%]
   1:kernel-PAE             ########################################### [100%]








4，安装完后，grub.conf文件会被改修，我们只需要修改default=0,
[root@tgds ~]# more  /etc/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/sda2
#          initrd /initrd-version.img
#boot=/dev/sda
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title CentOS (2.6.18-164.el5PAE)
        root (hd0,0)
        kernel /vmlinuz-2.6.18-164.el5PAE ro root=LABEL=/ rhgb quiet
        initrd /initrd-2.6.18-164.el5PAE.img
title CentOS (2.6.18-164.el5)
        root (hd0,0)
        kernel /vmlinuz-2.6.18-164.el5 ro root=LABEL=/ rhgb quiet
        initrd /initrd-2.6.18-164.el5.img
5，查看安装的内核
[root@tgds ~]# ll /boot/
总计 11078
-rw-r--r-- 1 root root   68663 2009-09-03 config-2.6.18-164.el5
-rw-r--r-- 1 root root   68616 2009-09-03 config-2.6.18-164.el5PAE
drwxr-xr-x 2 root root    1024 11-17 23:22 grub
-rw------- 1 root root 2605511 2011-04-01 initrd-2.6.18-164.el5.img
-rw------- 1 root root 2606593 11-17 23:12 initrd-2.6.18-164.el5PAE.img
drwx------ 2 root root   12288 2011-04-01 lost+found
-rw-r--r-- 1 root root   80032 2009-03-13 message
-rw-r--r-- 1 root root  107405 2009-09-03 symvers-2.6.18-164.el5.gz
-rw-r--r-- 1 root root  107459 2009-09-03 symvers-2.6.18-164.el5PAE.gz
-rw-r--r-- 1 root root  954947 2009-09-03 System.map-2.6.18-164.el5
-rw-r--r-- 1 root root  952431 2009-09-03 System.map-2.6.18-164.el5PAE
-rw-r--r-- 1 root root 1855924 2009-09-03 vmlinuz-2.6.18-164.el5
-rw-r--r-- 1 root root 1852564 2009-09-03 vmlinuz-2.6.18-164.el5PAE




6，reboot重新启动，发现内存全部识别了。
随手记录一下！