Docker.io 是轻量级的“容器引擎+映像仓库”，在LXC（linux轻量级容器）的基础上构建，可以运行任何应用程序。

docker.io的核心层由以下几个部分组成:

1、可执行程序，“/usr/bin/docker”

2、docker.io网站上有一系列创建好的操作系统和应用程序映像

3、AUFS（另一个统一文件系统）来实现文件系统的快照，文件变化，控制只读或读写的需求。

4、LXC（Linux轻量级容器）

5、Cgroups（各种资源和命名空间的管理）

在本文写作的时候，最新版本是0.5.3，但目前开发很活跃，一些功能和特性可能在新版本中会发生变化。

按下面的步骤安装docker.io：

0、安装centos6.x

1、因为selinux和LXC有冲突，所以需要禁用

1. [root@localhost ~]# cat /etc/selinux/config
2. # This file controls the state of SELinux on the system.
3. # SELINUX= can take one of these three values:
4. # enforcing - SELinux security policy is enforced.
5. # permissive - SELinux prints warnings instead of enforcing.
6. # disabled - SELinux is fully disabled.
7. SELINUX=disabled
8. # SELINUXTYPE= type of policy in use. Possible values are:
9. # targeted - Only targeted network daemons are protected.
10. # strict - Full SELinux protection.
11. SELINUXTYPE=targeted

2、配置Fedora EPEL 源

1. sudo yum install http://ftp.riken.jp/Linux/fedora/epel/6/i386/epel-release-6-8.noarch.rpm

3、配置hop5.in源

1. cd /etc/yum.repos.d
2. sudo wget http://www.hop5.in/yum/el6/hop5.repo

4、安装docker-io

1. [root@localhost ~]# yum install docker-io
2. Loaded plugins: fastestmirror, security
3. Loading mirror speeds from cached hostfile
4. * base: centos.excellmedia.net
5. * epel: kartolo.sby.datautama.net.id
6. * extras: centos.excellmedia.net
7. * updates: centos.excellmedia.net
8. Setting up Install Process
9. Resolving Dependencies
10. --> Running transaction check
11. ---> Package docker-io.x86_64 0:0.5.3-4.el6 will be installed
12. --> Processing Dependency: lxc >= 0.8.0 for package: docker-io-0.5.3-4.el6.x86_64
13. --> Processing Dependency: kernel-ml-aufs >= 3.10.5 for package: docker-io-0.5.3-4.el6.x86_64
14. --> Running transaction check
15. ---> Package kernel-ml-aufs.x86_64 0:3.10.5-3.el6 will be installed
16. ---> Package lxc.x86_64 0:0.8.0-3.el6 will be installed
17. --> Processing Dependency: liblxc.so.0()(64bit) for package: lxc-0.8.0-3.el6.x86_64
18. --> Running transaction check
19. ---> Package lxc-libs.x86_64 0:0.8.0-3.el6 will be installed
20. --> Finished Dependency Resolution
22. Dependencies Resolved
24. ============================================================================================
25. Package Arch Version Repository Size
26. ============================================================================================
27. Installing:
28. docker-io x86_64 0.5.3-4.el6 hop5 1.2 M
29. Installing for dependencies:
30. kernel-ml-aufs x86_64 3.10.5-3.el6 hop5 33 M
31. lxc x86_64 0.8.0-3.el6 hop5 81 k
32. lxc-libs x86_64 0.8.0-3.el6 hop5 75 k
34. Transaction Summary
35. ============================================================================================
36. Install 4 Package(s)
38. Total download size: 34 M
39. Installed size: 159 M
40. Is this ok [y/N]: y
41. Downloading Packages:
42. (1/4): docker-io-0.5.3-4.el6.x86_64.rpm | 1.2 MB 00:03
43. (2/4): kernel-ml-aufs-3.10.5-3.el6.x86_64.rpm | 33 MB 00:33
44. (3/4): lxc-0.8.0-3.el6.x86_64.rpm | 81 kB 00:00
45. (4/4): lxc-libs-0.8.0-3.el6.x86_64.rpm | 75 kB 00:00
46. --------------------------------------------------------------------------------------------
47. Total 896 kB/s | 34 MB 00:39
48. Running rpm_check_debug
49. Running Transaction Test
50. Transaction Test Succeeded
51. Running Transaction
52. Installing : lxc-libs-0.8.0-3.el6.x86_64 1/4
53. Installing : lxc-0.8.0-3.el6.x86_64 2/4
54. Installing : kernel-ml-aufs-3.10.5-3.el6.x86_64 3/4
55. Installing : docker-io-0.5.3-4.el6.x86_64 4/4
56. Verifying : kernel-ml-aufs-3.10.5-3.el6.x86_64 1/4
57. Verifying : lxc-0.8.0-3.el6.x86_64 2/4
58. Verifying : lxc-libs-0.8.0-3.el6.x86_64 3/4
59. Verifying : docker-io-0.5.3-4.el6.x86_64 4/4
61. Installed:
62. docker-io.x86_64 0:0.5.3-4.el6
64. Dependency Installed:
65. kernel-ml-aufs.x86_64 0:3.10.5-3.el6 lxc.x86_64 0:0.8.0-3.el6
66. lxc-libs.x86_64 0:0.8.0-3.el6
68. Complete!
69. [root@localhost ~]#

5、检查安装情况

1. [root@localhost ~]# docker -h
2. Usage of docker:
3. -D=false: Debug mode
4. -H=[unix:///var/run/docker.sock]: tcp://host:port to bind/connect to or unix://path/to/socket to use
5. -api-enable-cors=false: Enable CORS requests in the remote api.
6. -b="": Attach containers to a pre-existing network bridge. Use 'none' to disable container networking
7. -d=false: Daemon mode
8. -dns="": Set custom dns servers
9. -g="/var/lib/docker": Path to graph storage base dir.
10. -p="/var/run/docker.pid": File containing process PID
11. -r=false: Restart previously running containers

6、要想docker正常运行还需要在/etc/fstab里增加cgroup文件系统

1. [root@localhost ~]# echo "none /sys/fs/cgroup cgroup defaults 0 0" >> /etc/fstab
3. [root@localhost ~]# mount /sys/fs/cgroup

只有重新启动才能挂载/sys/fs/cgroup（因为当前运行的内核不支持cgroup），所以上面挂载的命令也可以不执行，但系统需要重新启动。

7、重启系统，选择“3.10.5-3.el6.x86_64”内核

8、系统启动后，确认当前运行的内核

1. [root@localhost ~]# uname -r
2. 3.10.5-3.el6.x86_64
4. [root@localhost ~]# grep aufs /proc/filesystems
5. nodev aufs

9、以守护模式运行docker.io（在一个新的终端里）

1. [root@localhost ~]# docker -d
2. 2013/08/21 07:47:07 WARNING: Your kernel does not support cgroup swap limit.
3. 2013/08/21 07:47:07 Listening for HTTP on /var/run/docker.sock (unix)

10、在centos6.4容器里输出hello world

1. [root@localhost ~]# docker run centos:6.4 echo "hello world"
2. 2013/08/21 07:48:41 POST /v1.4/containers/create
3. 2013/08/21 07:48:41 POST /v1.4/containers/c6bc9e80097e/start
4. 2013/08/21 07:48:41 POST /v1.4/containers/c6bc9e80097e/attach?logs=1&stderr=1&stdout=1&stream=1
5. hello world

11、从容器里测试ping

1. [root@localhost ~]# docker -dns '8.8.8.8' run centos:6.4 ping -c 3 yahoo.com
2. 2013/08/21 08:02:15 POST /v1.4/containers/create
3. 2013/08/21 08:02:15 POST /v1.4/containers/c40a1244f9bc/start
4. 2013/08/21 08:02:15 POST /v1.4/containers/c40a1244f9bc/attach?logs=1&stderr=1&stdout=1&stream=1
5. PING yahoo.com (98.138.253.109) 56(84) bytes of data.
6. 64 bytes from ir1.fp.vip.ne1.yahoo.com (98.138.253.109): icmp_seq=1 ttl=48 time=323 ms
7. 64 bytes from ir1.fp.vip.ne1.yahoo.com (98.138.253.109): icmp_seq=2 ttl=48 time=329 ms
8. 64 bytes from ir1.fp.vip.ne1.yahoo.com (98.138.253.109): icmp_seq=3 ttl=49 time=302 ms
10. --- yahoo.com ping statistics ---
11. 3 packets transmitted, 3 received, 0% packet loss, time 2304ms
12. rtt min/avg/max/mdev = 302.032/318.318/329.656/11.807 ms

常见错误：

"DNS/Networking Errors inside the docker"

1. [root@localhost ~]# docker -dns="8.8.8.8" run centos:6.4 yum install hiphop-php
2. 2013/08/21 07:53:05 POST /v1.4/containers/create
3. 2013/08/21 07:53:05 POST /v1.4/containers/6d9fef14bd1a/start
4. 2013/08/21 07:53:05 POST /v1.4/containers/6d9fef14bd1a/attach?logs=1&stderr=1&stdout=1&stream=1
5. Loaded plugins: fastestmirror
6. Error: Cannot retrieve repository metadata (repomd.xml) for repository: base. Please verify its path and try again
7. Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=6&arch=x86_64&repo=os error was
8. 14: PYCURL ERROR 6 - "Couldn't resolve host 'mirrorlist.centos.org'"

可以执行下面的命令来重置docker的运行环境，从而解决上述问题。

1. pkill docker
2. iptables -t nat -F
3. ifconfig docker0 down
4. brctl delbr docker0
5. docker -d

原文发布时间为：2014-01-03

本文来自云栖社区合作伙伴“Linux中国”