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title = "Installation on CentOS"
description = "Instructions for installing Docker on CentOS"
keywords = ["Docker, Docker documentation, requirements, linux, centos, epel, docker.io, docker-io"]
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parent = "smn_linux"
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<![end-metadata]-->
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# CentOS
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Docker is supported on the following versions of CentOS:
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* 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 ](https://www.centos.org ) 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:
< table >
< tr >
< th > Version< / th >
< th > Package name< / th >
< / tr >
< tr >
< td > 6.5 and higher< / td >
< td >
< p >
< a href = "https://get.docker.com/rpm/1.7.0/centos-6/RPMS/x86_64/docker-engine-1.7.0-1.el6.x86_64.rpm" >
https://get.docker.com/rpm/1.7.0/centos-6/RPMS/x86_64/docker-engine-1.7.0-1.el6.x86_64.rpm< / a >
< p >
< a href = "https://get.docker.com/rpm/1.7.0/centos-6/SRPMS/docker-engine-1.7.0-1.el6.src.rpm" >
https://get.docker.com/rpm/1.7.0/centos-6/SRPMS/docker-engine-1.7.0-1.el6.src.rpm< / a >
< p >
< / p >
< / td >
< / tr >
< tr >
< td > 7.X< / td >
< td >
< p >
< a href = "https://get.docker.com/rpm/1.7.0/centos-7/RPMS/x86_64/docker-engine-1.7.0-1.el7.centos.x86_64.rpm" >
https://get.docker.com/rpm/1.7.0/centos-7/RPMS/x86_64/docker-engine-1.7.0-1.el7.centos.x86_64.rpm< / a >
< / p >
< p >
< a href = "https://get.docker.com/rpm/1.7.0/centos-7/SRPMS/docker-engine-1.7.0-1.el7.centos.src.rpm" >
https://get.docker.com/rpm/1.7.0/centos-7/SRPMS/docker-engine-1.7.0-1.el7.centos.src.rpm< / a >
< / p >
< / td >
< / tr >
< / table >
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This procedure depicts an installation on version 6.5. If you are installing on
7.X, substitute that package for your installation.
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1. Log into your machine as a user with `sudo` or `root` privileges.
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2. Make sure your existing packages are up-to-date.
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$ sudo yum update
3. Download the Docker RPM to the current directory.
$ curl -O -sSL https://get.docker.com/rpm/1.7.0/centos-6/RPMS/x86_64/docker-engine-1.7.0-1.el6.x86_64.rpm
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4. Use `yum` to install the package.
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$ sudo yum localinstall --nogpgcheck docker-engine-1.7.0-1.el6.x86_64.rpm
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5. Start the Docker daemon.
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$ sudo service docker start
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6. Verify `docker` is installed correctly by running a test image in a container.
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$ 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:aa03e5d0d5553b4c3473e89c8619cf79df368babd1.7.0cf5daeb82aab55838d
Status: Downloaded newer image for hello-world:latest
Hello from Docker.
This message shows that your installation appears to be working correctly.
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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.
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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
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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.
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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.
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>**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*](/articles/security/#docker-daemon-attack-surface) for details.
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To create the `docker` group and add your user:
1. Log into Centos as a user with `sudo` privileges.
2. Create the `docker` group and add your user.
`sudo usermod -aG docker your_username`
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3. Log out and log back in.
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This ensures your user is running with the correct permissions.
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4. Verify your work by running `docker` without `sudo` .
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$ docker run hello-world
## Start the docker daemon at boot
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To ensure Docker starts when you boot your system, do the following:
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$ sudo chkconfig docker on
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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 ](/articles/systemd/ ).
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## Uninstall
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You can uninstall the Docker software with `yum` .
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1. List the package you have installed.
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$ yum list installed | grep docker
yum list installed | grep docker
docker-engine.x86_64 1.7.0-1.el6
@/docker -engine-1.7.0-1.el6.x86_64.rpm
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2. Remove the package.
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$ sudo yum -y remove docker-engine.x86_64
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This command does not remove images, containers, volumes, or user-created
configuration files on your host.
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3. To delete all images, containers, and volumes, run the following command:
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$ rm -rf /var/lib/docker
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4. Locate and delete any user-created configuration files.