本文轉自：http://www.511yj.com/centos-yum-kernel.html
今天想在centos6.5安裝docker，在網上查了說centos6.5需要64位的，內核需要升級到3.x以上（centos6.5本來是2.6），終於看到一篇文章是可以的，於是記錄下來。
了解一下elrepo
elrepo是CentOS十分有用的穩定的軟件源，與其他軟件源不一樣的是，這個第三方源主要是提供硬件驅動、內核更新方面的支持，如顯卡、無線網卡、內核等等，現在已經支持centos7.x+,更新較快。
1、查看centos版本
[root@localhost ~]# cat /etc/centos-release
CentOS release 6.4 (Final)
2、查看內核
[root@localhost ~]# uname -r
2.6.32-358.el6.x86_64
3、首先你要做的就是導入public key
[root@localhost ~]# rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
4、然后安裝ELRepo到CentOS-6.x中
注意：elrepo-release-6-6.el6.elrepo.noarch.rpm這是針對centos6.0+版本的，網上的很多的文章都是錯誤的-6-5
1、安裝 ELRepo for RHEL-6, SL-6 or CentOS-6:
rpm -Uvh http://www.elrepo.org/elrepo-release-6-6.el6.elrepo.noarch.rpm
2、安裝 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、安裝 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)
執行安裝！
[root@localhost ~]# rpm -Uvh http://www.elrepo.org/elrepo-release-6-6.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、安裝kernel-lt（lt=long-term）
[root@localhost ~]# yum --enablerepo=elrepo-kernel install kernel-lt -y
國外網速較慢，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
或者安裝kernel-ml（ml=mainline）
yum --enablerepo=elrepo-kernel install kernel-ml -y
二者任選其一！
6、編輯grub.conf文件，修改Grub引導順序
vim /etc/grub.conf
按 i 把 default=1修改為 default=0,按esc 鍵，輸入 ：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：
確認剛安裝好的內核在哪個位置，然后設置default值（從0開始），一般新安裝的內核在第一個位置，所以設置default=0。
7、重啟centos
[root@localhost ~]# reboot
8、重新查看內核
[root@localhost ~]# uname -r
3.10.103-1.el6.elrepo.x86_64
升級成功！