Docker is supported on the following versions of CentOS:
CentOS 7.X
CentOS 6.5 or higher
Installation on other binary compatible EL6/EL7 distributions such as Scientific
Linux might succeed, but Docker does not test or support Docker on these
distributions.
This page instructs you to install using Docker-managed release packages and
installation mechanisms. Using these packages ensures you get the latest release
of Docker. If you wish to install using CentOS-managed packages, consult your
CentOS documentation.
Prerequisites
Docker requires a 64-bit installation regardless of your CentOS version. Also,
your kernel must be 3.10 at minimum. CentOS 7 runs the 3.10 kernel, 6.5 does
not. We make an exception for CentOS 6.5. To run Docker on
CentOS-6.5 or later, you need kernel 2.6.32-431 or
higher.
To check your current kernel version, open a terminal and use uname -r to
display your kernel version:
$ uname -r
2.6.32-431.el6.x86_64
Finally, is it recommended that you fully update your system. Please keep in
mind that CentOS 6 should be fully patched to fix any potential kernel bugs. Any
reported kernel bugs may have already been fixed on the latest kernel packages
Install
You use the same installation procedure for all versions of CentOS,
only the package you install differs. There are two packages to choose from:
Verify docker is installed correctly by running a test image in a container.
$ sudo docker run hello-world
Unable to find image 'hello-world:latest' locally
latest: Pulling from hello-world
a8219747be10: Pull complete
91c95931e552: Already exists
hello-world:latest: The image you are pulling has been verified. Important: image verification is a tech preview feature and should not be relied on to provide security.
Digest: sha256:aa03e5d0d5553b4c3473e89c8619cf79df368babd1.7.1cf5daeb82aab55838d
Status: Downloaded newer image for hello-world:latest
Hello from Docker.
This message shows that your installation appears to be working correctly.
To generate this message, Docker took the following steps:
1. The Docker client contacted the Docker daemon.
2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
(Assuming it was not already locally available.)
3. The Docker daemon created a new container from that image which runs the
executable that produces the output you are currently reading.
4. The Docker daemon streamed that output to the Docker client, which sent it
to your terminal.
To try something more ambitious, you can run an Ubuntu container with:
$ docker run -it ubuntu bash
For more examples and ideas, visit:
http://docs.docker.com/userguide/
Create a docker group
The docker daemon binds to a Unix socket instead of a TCP port. By default
that Unix socket is owned by the user root and other users can access it with
sudo. For this reason, docker daemon always runs as the root user.
To avoid having to use sudo when you use the docker command, create a Unix
group called docker and add users to it. When the docker daemon starts, it
makes the ownership of the Unix socket read/writable by the docker group.
Warning: The docker group is equivalent to the root user; For details
on how this impacts security in your system, see Docker Daemon Attack
Surface for details.
To create the docker group and add your user:
Log into Centos as a user with sudo privileges.
Create the docker group and add your user.
sudo usermod -aG docker your_username
Log out and log back in.
This ensures your user is running with the correct permissions.
Verify your work by running docker without sudo.
$ docker run hello-world
Start the docker daemon at boot
To ensure Docker starts when you boot your system, do the following:
$ sudo chkconfig docker on
If you need to add an HTTP Proxy, set a different directory or partition for the
Docker runtime files, or make other customizations, read our Systemd article to
learn how to customize your Systemd Docker daemon options.
Uninstall
You can uninstall the Docker software with yum.
List the package you have installed.
$ yum list installed | grep docker
yum list installed | grep docker
docker-engine.x86_64 1.7.1-1.el6
@/docker-engine-1.7.1-1.el6.x86_64.rpm
Remove the package.
$ sudo yum -y remove docker-engine.x86_64
This command does not remove images, containers, volumes, or user-created
configuration files on your host.
To delete all images, containers, and volumes, run the following command:
$ rm -rf /var/lib/docker
Locate and delete any user-created configuration files.
