yum 不能安裝kernel包

OS:Centos 6.2 64bit

錯誤信息

[root@LNMP1 ~]# yum install kernel-headers
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirrors.163.com
 * extras: mirrors.163.com
 * updates: mirrors.163.com
Setting up Install Process
No package kernel-headers available.
Error: Nothing to do

修改yum配置文件

[root@LNMP1 ~]#  vi /etc/yum.conf 

[main]
cachedir=/var/cache/yum/$basearch/$releasever
keepcache=0
debuglevel=2
logfile=/var/log/yum.log
exactarch=1
obsoletes=1
gpgcheck=1
plugins=1
#exclude=kernel*                         //把該行註釋點，默承認能屏蔽了kernel包


installonly_limit=5
bugtracker_url=http://bugs.centos.org/set_project.php?project_id=16&ref=http://bugs.centos.org/bug_report_page.php?category=yum
distroverpkg=centos-release