Wednesday, August 21, 2013

Installing on centos 6.4 (64-bit)

NOTES: epel has another package called docker (which is a KDE docking application and is not related to this). So, you will get an error performing these steps, if you have that package already installed.

UPDATE-1: Docker version-0.6.1 is released. Upgrade instructions are available here

UPDATE-2: Docker version-0.6.2 is released. is the lightweight "container engine + image repository" built on top of LXC (linux lightweight containers) to ship any application.

At the core of there are
  1.  an application "/usr/bin/docker" 
  2.  set of pre-created operating-system/application images hosted with ""
  3.  AUFS (Another Union filesystem) to take care of snapshots, diffs, ro/rw requirements
  4. LXC (Linux lightweight containers)
  5. cgroups (for resource management and namespacing)
As of writing this blog, the latest version is 0.5.3 . The project is actively being developed and things can change in near future.

Follow these instructions to get installed on your system.

0. Install centos 6.x

1. Disable selinux as it interferes with functionality of LXC

[root@localhost ~]# cat /etc/selinux/config 
# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#       enforcing - SELinux security policy is enforced.
#       permissive - SELinux prints warnings instead of enforcing.
#       disabled - SELinux is fully disabled.
# SELINUXTYPE= type of policy in use. Possible values are:
#       targeted - Only targeted network daemons are protected.
#       strict - Full SELinux protection.
2. Download and setup Fedora EPEL Repository

sudo yum install

3. Setup repository

cd /etc/yum.repos.d
sudo wget

4. Install docker-io package

[root@localhost ~]# yum install docker-io
Loaded plugins: fastestmirror, security
Loading mirror speeds from cached hostfile
 * base:
 * epel:
 * extras:
 * updates:
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package docker-io.x86_64 0:0.5.3-4.el6 will be installed
--> Processing Dependency: lxc >= 0.8.0 for package: docker-io-0.5.3-4.el6.x86_64
--> Processing Dependency: kernel-ml-aufs >= 3.10.5 for package: docker-io-0.5.3-4.el6.x86_64
--> Running transaction check
---> Package kernel-ml-aufs.x86_64 0:3.10.5-3.el6 will be installed
---> Package lxc.x86_64 0:0.8.0-3.el6 will be installed
--> Processing Dependency: for package: lxc-0.8.0-3.el6.x86_64
--> Running transaction check
---> Package lxc-libs.x86_64 0:0.8.0-3.el6 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

 Package                   Arch              Version                  Repository       Size
 docker-io                 x86_64            0.5.3-4.el6              hop5            1.2 M
Installing for dependencies:
 kernel-ml-aufs            x86_64            3.10.5-3.el6             hop5             33 M
 lxc                       x86_64            0.8.0-3.el6              hop5             81 k
 lxc-libs                  x86_64            0.8.0-3.el6              hop5             75 k

Transaction Summary
Install       4 Package(s)

Total download size: 34 M
Installed size: 159 M
Is this ok [y/N]: y
Downloading Packages:
(1/4): docker-io-0.5.3-4.el6.x86_64.rpm                              | 1.2 MB     00:03     
(2/4): kernel-ml-aufs-3.10.5-3.el6.x86_64.rpm                        |  33 MB     00:33     
(3/4): lxc-0.8.0-3.el6.x86_64.rpm                                    |  81 kB     00:00     
(4/4): lxc-libs-0.8.0-3.el6.x86_64.rpm                               |  75 kB     00:00     
Total                                                       896 kB/s |  34 MB     00:39     
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing : lxc-libs-0.8.0-3.el6.x86_64                                              1/4 
  Installing : lxc-0.8.0-3.el6.x86_64                                                   2/4 
  Installing : kernel-ml-aufs-3.10.5-3.el6.x86_64                                       3/4 
  Installing : docker-io-0.5.3-4.el6.x86_64                                             4/4 
  Verifying  : kernel-ml-aufs-3.10.5-3.el6.x86_64                                       1/4 
  Verifying  : lxc-0.8.0-3.el6.x86_64                                                   2/4 
  Verifying  : lxc-libs-0.8.0-3.el6.x86_64                                              3/4 
  Verifying  : docker-io-0.5.3-4.el6.x86_64                                             4/4 

  docker-io.x86_64 0:0.5.3-4.el6                                                            

Dependency Installed:
  kernel-ml-aufs.x86_64 0:3.10.5-3.el6               lxc.x86_64 0:0.8.0-3.el6              
  lxc-libs.x86_64 0:0.8.0-3.el6                     

[root@localhost ~]#

5. See the package is installed correctly

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

6. Add cgroup filesystem to /etc/fstab , so that docker will work correctly

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

Per "Peter Zimmerman" a reboot is needed to actually mount /sys/fs/cgroup (due to the kernel doesn't have cgroup support). So, the above mount step is not really needed. As its used only upon reboot.

7. Reboot the system ; make sure to select "3.10.5-3.el6.x86_64" kernel version while booting.

8. Once system is up and running, make sure you are on right kernel

[root@localhost ~]# uname -r

[root@localhost ~]# grep aufs /proc/filesystems 
nodev   aufs
9. Start the in daemon mode (in a different terminal)

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

10. Print hello world from a centos 6.4 container.

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

11. Ping from inside the container
[root@localhost ~]# docker -dns '' run centos:6.4 ping -c 3
2013/08/21 08:02:15 POST /v1.4/containers/create
2013/08/21 08:02:15 POST /v1.4/containers/c40a1244f9bc/start
2013/08/21 08:02:15 POST /v1.4/containers/c40a1244f9bc/attach?logs=1&stderr=1&stdout=1&stream=1
PING ( 56(84) bytes of data.
64 bytes from ( icmp_seq=1 ttl=48 time=323 ms
64 bytes from ( icmp_seq=2 ttl=48 time=329 ms
64 bytes from ( icmp_seq=3 ttl=49 time=302 ms

--- ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2304ms
rtt min/avg/max/mdev = 302.032/318.318/329.656/11.807 ms


"DNS/Networking Errors inside the docker"

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

Please issue the following commands, so that docker and its environment will be reset and above issue will be taken care of.

pkill docker
iptables -t nat -F
ifconfig docker0 down
brctl delbr docker0
docker -d

CREDITS: Thanks to sciurus for doing the hardwork in creating the spec file for kernel-ml-aufs.


  1. "epel has another package called docker (which is a KDE docking application and is not related to this). So, you will get an error performing these steps, if you have that package already installed." - what do you think about renaming docker from to lxc-docker to avoid this error. This is done already for debian: If you use kernel, docker spec from: we can make pull request to @sciurus repo or ask him to do this.

    1. Actually, that note isn't valid anymore as the package is "docker-io", the reason why it isn't lxc-docker is due to branding issues (i don't work for docker). I feel is more than just LXC. So, i prefer to keep it without lxc- prefix. But, if people prefer lxc-* , i can add Provides section.

      I am aware of @sciurus repo as i have originally created kernel rpm from that repo. In his repo, he just pulls a binary which is compiled by docker guys. But, i am building the binary from source to keep it compatible with golang that i have.

  2. Thank you for this excellent work. This Blog helped me with my first docker-steps. One suggestion. It costs me a lot of time that mounting of /sys/fs/cgroups is not possible during point 6 in your list. After 6(a) you have to reboot the system. After this reboot /sys/fs/cgroups exists an then mount ist done.

    1. Thanks. I have updated the blog to make mount of /sys/fs/cgroups optional (before reboot).

  3. Thank you for this article Naresh.
    I've converted your article into a Vagrantfile which, once booted, will have docker ready to go:

  4. Thanks for providing this centos docker repository it really helped me to get started.
    Maybe I just overlooked it but can you add a init script.
    Here is my version of the init script, feel free to adapt and use it:

    And here is a openstack version which will give the nova group pemrissions to execute docker:

    thanks again

    1. Thanks Daniel. I'll try to add this initscript with next build.

  5. I am getting this error, when I try to install docker-io thru yum:

    hop5/primary_db | 87 kB 00:00 [Errno -3] Error performing checksum
    Trying other mirror.
    Error: failure: repodata/68c97ab6e2529b1afc8da34b0da1878055b63b1fd2b5cf255ee4510245bbc0bd-primary.sqlite.bz2 from hop5: [Errno 256] No more mirrors to try.

    Any idea, what is wrong and how to resolve it?

    1. Hello,

      It could possibly due to network maint by my ISP. Try again now

      curl -I
      HTTP/1.1 200 OK
      Server: nginx/1.4.3
      Date: Sat, 30 Nov 2013 04:12:24 GMT
      Content-Type: text/plain
      Content-Length: 89289
      Connection: keep-alive
      Vary: Accept-Encoding
      Last-Modified: Sat, 19 Oct 2013 10:51:48 GMT
      Etag: "52626444.15cc9"
      Accept-Ranges: bytes