188 lines
6.0 KiB
Markdown
188 lines
6.0 KiB
Markdown
<!--[metadata]>
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+++
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title = "Installation on CentOS"
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description = "Instructions for installing Docker on CentOS"
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keywords = ["Docker, Docker documentation, requirements, linux, centos, epel, docker.io, docker-io"]
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[menu.main]
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parent = "smn_linux"
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weight=-4
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+++
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<![end-metadata]-->
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# CentOS
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Docker runs on CentOS 7.X. An installation on other binary compatible EL7
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distributions such as Scientific Linux might succeed, but Docker does not test
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or support Docker on these distributions.
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This page instructs you to install using Docker-managed release packages and
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installation mechanisms. Using these packages ensures you get the latest release
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of Docker. If you wish to install using CentOS-managed packages, consult your
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CentOS documentation.
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## Prerequisites
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Docker requires a 64-bit installation regardless of your CentOS version. Also,
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your kernel must be 3.10 at minimum, which CentOS 7 runs.
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To check your current kernel version, open a terminal and use `uname -r` to
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display your kernel version:
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$ uname -r
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3.10.0-229.el7.x86_64
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Finally, is it recommended that you fully update your system. Please keep in
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mind that your system should be fully patched to fix any potential kernel bugs.
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Any reported kernel bugs may have already been fixed on the latest kernel
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packages.
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## Install
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There are two ways to install Docker Engine. You can install using the `yum`
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package manager. Or you can use `curl` with the `get.docker.com` site. This
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second method runs an installation script which also installs via the `yum`
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package manager.
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### Install with yum
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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 yum packages are up-to-date.
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$ sudo yum update
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3. Add the yum repo.
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$ cat >/etc/yum.repos.d/docker.repo <<-EOF
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[dockerrepo]
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name=Docker Repository
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baseurl=https://yum.dockerproject.org/repo/main/centos/7
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enabled=1
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gpgcheck=1
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gpgkey=https://yum.dockerproject.org/gpg
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EOF
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4. Install the Docker package.
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$ sudo yum install docker-engine
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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
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Unable to find image 'hello-world:latest' locally
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latest: Pulling from hello-world
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a8219747be10: Pull complete
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91c95931e552: Already exists
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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.
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Digest: sha256:aa03e5d0d5553b4c3473e89c8619cf79df368babd1.7.1cf5daeb82aab55838d
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Status: Downloaded newer image for hello-world:latest
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Hello from Docker.
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This message shows that your installation appears to be working correctly.
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To generate this message, Docker took the following steps:
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1. The Docker client contacted the Docker daemon.
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2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
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(Assuming it was not already locally available.)
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3. The Docker daemon created a new container from that image which runs the
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executable that produces the output you are currently reading.
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4. The Docker daemon streamed that output to the Docker client, which sent it
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to your terminal.
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To try something more ambitious, you can run an Ubuntu container with:
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$ docker run -it ubuntu bash
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For more examples and ideas, visit:
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http://docs.docker.com/userguide/
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### Install with the script
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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 yum packages are up-to-date.
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$ sudo yum update
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3. Run the Docker installation script.
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$ curl -sSL https://get.docker.com/ | sh
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This script adds the `docker.repo` repository and installs Docker.
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4. Start the Docker daemon.
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$ sudo service docker start
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5. Verify `docker` is installed correctly by running a test image in a container.
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$ sudo docker run hello-world
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## Create a docker group
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The `docker` daemon binds to a Unix socket instead of a TCP port. By default
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that Unix socket is owned by the user `root` and other users can access it with
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`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
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group called `docker` and add users to it. When the `docker` daemon starts, it
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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
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>on how this impacts security in your system, see [*Docker Daemon Attack
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>Surface*](/articles/security/#docker-daemon-attack-surface) for details.
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To create the `docker` group and add your user:
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1. Log into Centos as a user with `sudo` privileges.
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2. Create the `docker` group and add your user.
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`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
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## 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
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Docker runtime files, or make other customizations, read our Systemd article to
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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
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yum list installed | grep docker
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docker-engine.x86_64 1.7.1-1.el7 @/docker-engine-1.7.1-1.el7.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
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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.
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