Docker官网上针对Centos的的安装需求如下:

Docker requires a 64-bit installation regardless of your CentOS version. Also,your kernel must be 3.10 at minimum,which CentOS 7 runs.

看来如果我们想在低于3.x内核的操作系统（比如Centos6.6）上装Docker最新版，势必要升级内核了。且不说升级内核步骤繁琐、容易出错，单就这种比较怪异的搭配：Centos6.x + Kerneol3.X + Docker1.11，就没有人能够保证其稳定性。故我的建议是设法在Centos6.6上安装较低版本的Docker。事实上，对于内核版本要大于3.10这个要求，是从Docker1.8.2版本开始的，Docker之前的版本是可以运行在较低内核版本之上的，比如1.7.1。

[root@bogon docker]# uname -a

Linux bogon 2.6.32-504.el6.x86_64 #1 SMP Wed Oct 15 04:27:16 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

[root@bogon docker]# cat /etc/redhat-release

CentOS release 6.6 (Final)

[root@bogon docker]# docker

bash: docker: command not found

[root@bogon docker]# yum install docker

Loaded plugins: fastestmirror,refresh-packagekit,security
Setting up Install Process
Loading mirror speeds from cached hostfile
* base: mirrors.tuna.tsinghua.edu.cn
* epel: dl.fedoraproject.org
* extras: mirrors.tuna.tsinghua.edu.cn
* updates: mirrors.tuna.tsinghua.edu.cn
http://repos.fedorapeople.org/repos/peter/erlang/epel-6/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found"
Trying other mirror.
To address this issue please refer to the below knowledge base article

https://access.redhat.com/articles/1320623

If above article doesn't help to resolve this issue please open a ticket with Red Hat Support.

No package docker available.
Error: Nothing to do

[root@bogon docker]# yum install docker-io

Loaded plugins: fastestmirror,security
Setting up Install Process
Loading mirror speeds from cached hostfile
* base: mirrors.tuna.tsinghua.edu.cn
* epel: pubmirror1.math.uh.edu
* extras: mirrors.tuna.tsinghua.edu.cn
* updates: mirrors.tuna.tsinghua.edu.cn
http://repos.fedorapeople.org/repos/peter/erlang/epel-6/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found"
Trying other mirror.
To address this issue please refer to the below knowledge base article

https://access.redhat.com/articles/1320623

If above article doesn't help to resolve this issue please open a ticket with Red Hat Support.

No package docker-io available.
Error: Nothing to do

可以看到，在Centos6.7的标准yum源中已经没有Docker的安装包了，这时，我们需要安装EPEL。

EPEL（Extra Packages for Enterprise Linux），企业版Linux额外包，RHEL分布非标准包的社区类库。安装如下：

[root@bogon docker]# rpm -iUvh http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm

Retrieving http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
warning: /var/tmp/rpm-tmp.em6i9i: Header V3 RSA/SHA256 Signature,key ID 0608b895: NOKEY
Preparing... ########################################### [100%]
1:epel-release ########################################### [100%]

接下来安装Docker1.7.1，在1.7.1中，安装包名称为docker-io，故我们的安装命令如下：

[root@bogon docker]# yum install docker-io

Loaded plugins: fastestmirror,security
Setting up Install Process
Loading mirror speeds from cached hostfile
epel/Metalink | 7.1 kB 00:00
* base: mirrors.tuna.tsinghua.edu.cn
* epel: mirrors.tuna.tsinghua.edu.cn
* extras: mirrors.tuna.tsinghua.edu.cn
* updates: mirrors.tuna.tsinghua.edu.cn
epel | 4.3 kB 00:00
epel/primary_db | 5.9 MB 00:13
http://repos.fedorapeople.org/repos/peter/erlang/epel-6/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found"
Trying other mirror.
To address this issue please refer to the below knowledge base article

https://access.redhat.com/articles/1320623

If above article doesn't help to resolve this issue please open a ticket with Red Hat Support.

Resolving Dependencies
--> Running transaction check
---> Package docker-io.x86_64 0:1.7.1-2.el6 will be installed
--> Processing Dependency: lxc for package: docker-io-1.7.1-2.el6.x86_64
--> Processing Dependency: libcgroup for package: docker-io-1.7.1-2.el6.x86_64
--> Running transaction check
---> Package libcgroup.x86_64 0:0.40.rc1-23.el6 will be installed
---> Package lxc.x86_64 0:1.0.9-1.el6 will be installed
--> Processing Dependency: lua-lxc(x86-64) = 1.0.9-1.el6 for package: lxc-1.0.9-1.el6.x86_64
--> Processing Dependency: lua-alt-getopt for package: lxc-1.0.9-1.el6.x86_64
--> Processing Dependency: liblxc.so.1()(64bit) for package: lxc-1.0.9-1.el6.x86_64
--> Running transaction check
---> Package lua-alt-getopt.noarch 0:0.7.0-1.el6 will be installed
---> Package lua-lxc.x86_64 0:1.0.9-1.el6 will be installed
--> Processing Dependency: lua-filesystem for package: lua-lxc-1.0.9-1.el6.x86_64
---> Package lxc-libs.x86_64 0:1.0.9-1.el6 will be installed
--> Running transaction check
---> Package lua-filesystem.x86_64 0:1.4.2-1.el6 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================================================================================================================================================================
Package Arch Version Repository Size
================================================================================================================================================================================================================================
Installing:
docker-io x86_64 1.7.1-2.el6 epel 4.6 M
Installing for dependencies:
libcgroup x86_64 0.40.rc1-23.el6 base 131 k
lua-alt-getopt noarch 0.7.0-1.el6 epel 6.9 k
lua-filesystem x86_64 1.4.2-1.el6 epel 24 k
lua-lxc x86_64 1.0.9-1.el6 epel 16 k
lxc x86_64 1.0.9-1.el6 epel 122 k
lxc-libs x86_64 1.0.9-1.el6 epel 257 k

Transaction Summary
================================================================================================================================================================================================================================
Install 7 Package(s)

Total download size: 5.1 M
Installed size: 20 M

Is this ok [y/N]: y

Downloading Packages:
(1/7): docker-io-1.7.1-2.el6.x86_64.rpm | 4.6 MB 00:10
(2/7): libcgroup-0.40.rc1-23.el6.x86_64.rpm | 131 kB 00:00
(3/7): lua-alt-getopt-0.7.0-1.el6.noarch.rpm | 6.9 kB 00:00
(4/7): lua-filesystem-1.4.2-1.el6.x86_64.rpm | 24 kB 00:00
(5/7): lua-lxc-1.0.9-1.el6.x86_64.rpm | 16 kB 00:00
(6/7): lxc-1.0.9-1.el6.x86_64.rpm | 122 kB 00:00
(7/7): lxc-libs-1.0.9-1.el6.x86_64.rpm | 257 kB 00:00
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Total 457 kB/s | 5.1 MB 00:11
warning: rpmts_HdrFromFdno: Header V3 RSA/SHA256 Signature,key ID 0608b895: NOKEY
Retrieving key from file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6
Importing GPG key 0x0608B895:
Userid : EPEL (6) <epel@fedoraproject.org>
Package: epel-release-6-8.noarch (installed)
From : /etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6

Is this ok [y/N]: y

Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
Warning: RPMDB altered outside of yum.
Installing : lxc-libs-1.0.9-1.el6.x86_64 1/7
Installing : lua-filesystem-1.4.2-1.el6.x86_64 2/7
Installing : lua-lxc-1.0.9-1.el6.x86_64 3/7
Installing : libcgroup-0.40.rc1-23.el6.x86_64 4/7
Installing : lua-alt-getopt-0.7.0-1.el6.noarch 5/7
Installing : lxc-1.0.9-1.el6.x86_64 6/7
Installing : docker-io-1.7.1-2.el6.x86_64 7/7
Verifying : lua-lxc-1.0.9-1.el6.x86_64 1/7
Verifying : lxc-libs-1.0.9-1.el6.x86_64 2/7
Verifying : lxc-1.0.9-1.el6.x86_64 3/7
Verifying : docker-io-1.7.1-2.el6.x86_64 4/7
Verifying : lua-alt-getopt-0.7.0-1.el6.noarch 5/7
Verifying : libcgroup-0.40.rc1-23.el6.x86_64 6/7
Verifying : lua-filesystem-1.4.2-1.el6.x86_64 7/7

Installed:
docker-io.x86_64 0:1.7.1-2.el6

Dependency Installed:
libcgroup.x86_64 0:0.40.rc1-23.el6 lua-alt-getopt.noarch 0:0.7.0-1.el6 lua-filesystem.x86_64 0:1.4.2-1.el6 lua-lxc.x86_64 0:1.0.9-1.el6 lxc.x86_64 0:1.0.9-1.el6 lxc-libs.x86_64 0:1.0.9-1.el6

Complete!

[root@bogon docker]# docker -v

Docker version 1.7.1,build 786b29d/1.7.1

安装完成！