今天想在centos6.5安装docker，在网上查了说centos6.5需要64位的，内核需要升级到3.x以上（centos6.5本来是2.6），终于看到一篇文章是可以的，于是记录下来。

了解一下elrepo

elrepo是CentOS十分有用的稳定的软件源，与其他软件源不一样的是，这个第三方源主要是提供硬件驱动、内核更新方面的支持，如显卡、无线网卡、内核等等，现在已经支持centos7.x+,更新较快。

1、查看centos版本

[root@localhost ~]# cat /etc/centos-release 
CentOS release 6.4 (Final)

2、查看内核

[root@localhost ~]# uname -r
2.6.32-358.el6.x86_64

3、首先你要做的就是导入public key

[root@localhost ~]# rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org

4、然后安装ELRepo到CentOS-6.x中

注意：
elrepo-release-6-6.el6.elrepo.noarch.rpm这是针对centos6.0+版本的，网上的很多的文章都是错误的-6-5
1、安装 ELRepo for RHEL-6, SL-6 or CentOS-6:

rpm -Uvh http://www.elrepo.org/elrepo-release-6-8.el6.elrepo.noarch.rpm

2、安装 ELRepo for RHEL-7, SL-7 or CentOS-7:

rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-2.el7.elrepo.noarch.rpm (external link)

3、安装 ELRepo for RHEL-5, SL-5 or CentOS-5:

rpm -Uvh http://www.elrepo.org/elrepo-release-5-5.el5.elrepo.noarch.rpm (external link)

执行安装！

[root@localhost ~]# rpm -Uvh http://www.elrepo.org/elrepo-release-6-8.el6.elrepo.noarch.rpm

返回：

Retrieving http://www.elrepo.org/elrepo-release-6-6.el6.elrepo.noarch.rpm
Preparing...                ########################################### [100%]
   1:elrepo-release         ########################################### [100%]

5、安装kernel-lt（lt=long-term）

[root@localhost ~]# yum --enablerepo=elrepo-kernel install kernel-lt -y

国外网速较慢，耐心等待....返回：

........
 * base: mirror.bit.edu.cn
 * elrepo: repos.lax-noc.com
 * elrepo-kernel: mirrors.tuna.tsinghua.edu.cn
 * extras: mirrors.sina.cn
 * updates: mirror.bit.edu.cn
base                                                                         | 3.7 kB     00:00     
elrepo                                                                       | 2.9 kB     00:00     
elrepo/primary_db                                                            | 716 kB     00:45     
https://mirrors.tuna.tsinghua.edu.cn/elrepo/kernel/el6/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 6 - "Couldn't resolve host 'mirrors.tuna.tsinghua.edu.cn'"
Trying other mirror.
elrepo-kernel                                                                | 2.9 kB     00:00     
elrepo-kernel/primary_db                                                     |  19 kB     00:00     
extras                                                                       | 3.4 kB     00:00     
extras/primary_db                                                            |  37 kB     00:00     
updates                                                                      | 3.4 kB     00:00     
updates/primary_db                                                           | 2.0 MB     00:01     
Setting up Install Process
Resolving Dependencies
--> Running transaction check
.....
Total download size: 33 M
Installed size: 154 M
Downloading Packages:
http://repos.lax-noc.com/elrepo/kernel/el6/x86_64/RPMS/kernel-lt-3.10.103-1.el6.elrepo.x86_64.rpm: [Errno 12] Timeout on http://repos.lax-noc.com/elrepo/kernel/el6/x86_64/RPMS/kernel-lt-3.10.103-1.el6.elrepo.x86_64.rpm: (28, 'Operation too slow. Less than 1 bytes/sec transfered the last 30 seconds')
Trying other mirror.
kernel-lt-3.10.103-1.el6.elrepo.x86_64.rpm                                                                                            |  33 MB     68:27     
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
Warning: RPMDB altered outside of yum.
  Installing : kernel-lt-3.10.103-1.el6.elrepo.x86_64                                                                                                    1/1 
  Verifying  : kernel-lt-3.10.103-1.el6.elrepo.x86_64                                                                                                    1/1 

Installed:
  kernel-lt.x86_64 0:3.10.103-1.el6.elrepo                                                                                                                   

Complete!
You have new mail in /var/spool/mail/root

或者安装kernel-ml（ml=mainline）

yum --enablerepo=elrepo-kernel install kernel-ml -y

二者任选其一！

6、编辑grub.conf文件，修改Grub引导顺序

vim /etc/grub.conf

按 i 把 default=1修改为 default=0,按esc 键，输入 ：wq保存退出。

# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE:  You do not have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /, eg.
#          root (hd0,0)
#          kernel /boot/vmlinuz-version ro root=/dev/sda1
#          initrd /boot/initrd-[generic-]version.img
#boot=/dev/sda
default=0
timeout=5
splashimage=(hd0,0)/boot/grub/splash.xpm.gz
hiddenmenu
title CentOS (3.10.28-1.el6.elrepo.x86_64)
        root (hd0,0)
        kernel /boot/vmlinuz-3.10.28-1.el6.elrepo.x86_64 ro root=UUID=0a05411f-16f2-4d69-beb0-2db4cefd3613 rd_NO_LUKS  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_MD crashkernel=auto LANG=en_US.UTF-8
 rd_NO_LVM rd_NO_DM rhgb quiet
        initrd /boot/initramfs-3.10.28-1.el6.elrepo.x86_64.img
title CentOS (2.6.32-431.3.1.el6.x86_64)
        root (hd0,0)
        kernel /boot/vmlinuz-2.6.32-431.3.1.el6.x86_64 ro root=UUID=0a05411f-16f2-4d69-beb0-2db4cefd3613 rd_NO_LUKS  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_MD crashkernel=auto LANG=en_US.UTF-8 r
d_NO_LVM rd_NO_DM rhgb quiet
        initrd /boot/initramfs-2.6.32-431.3.1.el6.x86_64.img
title CentOS (2.6.32-431.el6.x86_64)
        root (hd0,0)
        kernel /boot/vmlinuz-2.6.32-431.el6.x86_64 ro root=UUID=0a05411f-16f2-4d69-beb0-2db4cefd3613 rd_NO_LUKS  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_MD crashkernel=auto LANG=zh_CN.UTF-8 rd_NO
_LVM rd_NO_DM rhgb quiet
        initrd /boot/initramfs-2.6.32-431.el6.x86_64.img

注意：

确认刚安装好的内核在哪个位置，然后设置default值（从0开始），一般新安装的内核在第一个位置，所以设置default=0。

7、重启centos

[root@localhost ~]# reboot

8、重新查看内核

[root@localhost ~]# uname -r
3.10.103-1.el6.elrepo.x86_64

升级成功！