Docker installation in linux

Install Docker

If you use Ubuntu Trusty, Wily, or Xenial, install the linux-image-extra kernel package:

The Docker Group

If you prefer, you can set up a docker group to run Docker (instead of root ). However, as docker must have sudo access, docker receives the same access as root .

Run the following command to create a Docker group on Ubuntu:

Log out and back in.

Run the following command to create a Docker group on Debian:

You may specify a user instead of $ if you prefer.

Red Hat Enterprise Linux (RHEL) and CentOS

Docker runs on RHEL 7 and CentOS 7.

Install Docker

Install with Yum

1. Log into your system as a user with sudo privileges.
2. Update your system: sudo yum update -y .
3. Add the yum repo (use the code below for both RHEL 7 and CentOS 7):

Install with the Docker Installation Script

1. Log into your system as a user with sudo privileges.
2. Update your system:

This script adds the docker.repo repository and installs Docker.

The Docker Group

If you prefer, you can set up a docker group to run Docker (instead of root ). However, as docker must have sudo access, docker receives the same access as root .

Run the following command to create a Docker group and add your user to the group (replace USERNAME with your username):

Start Docker at Boot

Run one of the following:

• sudo chkconfig docker on
• sudo systemctl enable docker

Common Issues

Note: Members in the docker group have root privileges. Hardening Docker is covered in a future tutorial.

Ubuntu

Ubuntu Utopic 14.10 and 15.05 exist in Docker’s apt repository without official support. Upgrade to 15.10 or [preferably] 16.04. If you use Ubuntu 12.04, you need to update your kernel.

Debian

If you run Debian Wheezy, you need to update the sources with backports.

“Cannot connect to the Docker daemon. Is ‘docker daemon’ running on this host?”

If you get this error, you need to unset DOCKER_HOST; run unset DOCKER_HOST to clear the variable.

Next: Using Docker Hub
All about how to use Docker’s hosted registry.

By Runnable: The service that speeds up development by providing full-stack environments for every code branch.

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Post-installation steps for Linux

Estimated reading time: 15 minutes

This section contains optional procedures for configuring Linux hosts to work better with Docker.

Manage Docker as a non-root user

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 only access it using sudo . The Docker daemon always runs as the root user.

If you don’t want to preface the docker command with sudo , create a Unix group called docker and add users to it. When the Docker daemon starts, it creates a Unix socket accessible by members of the docker group.

The docker group grants privileges equivalent to the root user. For details on how this impacts security in your system, see Docker Daemon Attack Surface.

To create the docker group and add your user:

Create the docker group.

Add your user to the docker group.

Log out and log back in so that your group membership is re-evaluated.

If testing on a virtual machine, it may be necessary to restart the virtual machine for changes to take effect.

On a desktop Linux environment such as X Windows, log out of your session completely and then log back in.

On Linux, you can also run the following command to activate the changes to groups:

Verify that you can run docker commands without sudo .

This command downloads a test image and runs it in a container. When the container runs, it prints a message and exits.

If you initially ran Docker CLI commands using sudo before adding your user to the docker group, you may see the following error, which indicates that your

/.docker/ directory was created with incorrect permissions due to the sudo commands.

To fix this problem, either remove the

/.docker/ directory (it is recreated automatically, but any custom settings are lost), or change its ownership and permissions using the following commands:

Configure Docker to start on boot

Most current Linux distributions (RHEL, CentOS, Fedora, Debian, Ubuntu 16.04 and higher) use systemd to manage which services start when the system boots. On Debian and Ubuntu, the Docker service is configured to start on boot by default. To automatically start Docker and Containerd on boot for other distros, use the commands below:

To disable this behavior, use disable instead.

If you need to add an HTTP Proxy, set a different directory or partition for the Docker runtime files, or make other customizations, see customize your systemd Docker daemon options.

Use a different storage engine

For information about the different storage engines, see Storage drivers. The default storage engine and the list of supported storage engines depend on your host’s Linux distribution and available kernel drivers.

Configure default logging driver

Docker provides the capability to collect and view log data from all containers running on a host via a series of logging drivers. The default logging driver, json-file , writes log data to JSON-formatted files on the host filesystem. Over time, these log files expand in size, leading to potential exhaustion of disk resources.

To alleviate such issues, either configure the json-file logging driver to enable log rotation, use an alternative logging driver such as the “local” logging driver that performs log rotation by default, or use a logging driver that sends logs to a remote logging aggregator.

Configure where the Docker daemon listens for connections

By default, the Docker daemon listens for connections on a UNIX socket to accept requests from local clients. It is possible to allow Docker to accept requests from remote hosts by configuring it to listen on an IP address and port as well as the UNIX socket. For more detailed information on this configuration option take a look at “Bind Docker to another host/port or a unix socket” section of the Docker CLI Reference article.

Before configuring Docker to accept connections from remote hosts it is critically important that you understand the security implications of opening docker to the network. If steps are not taken to secure the connection, it is possible for remote non-root users to gain root access on the host. For more information on how to use TLS certificates to secure this connection, check this article on how to protect the Docker daemon socket.

Configuring Docker to accept remote connections can be done with the docker.service systemd unit file for Linux distributions using systemd, such as recent versions of RedHat, CentOS, Ubuntu and SLES, or with the daemon.json file which is recommended for Linux distributions that do not use systemd.

Configuring Docker to listen for connections using both the systemd unit file and the daemon.json file causes a conflict that prevents Docker from starting.

Configuring remote access with systemd unit file

Use the command sudo systemctl edit docker.service to open an override file for docker.service in a text editor.

Add or modify the following lines, substituting your own values.

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Install Docker Engine on Ubuntu

Estimated reading time: 12 minutes

Docker Desktop for Linux

Docker Desktop helps you build, share, and run containers easily on Mac and Windows as you do on Linux. Docker handles the complex setup and allows you to focus on writing the code. Thanks to the positive support we received on the subscription updates, we’ve started working on Docker Desktop for Linux which is the second-most popular feature request in our public roadmap. If you are interested in early access, sign up for our Developer Preview program.

To get started with Docker Engine on Ubuntu, make sure you meet the prerequisites, then install Docker.

Prerequisites

OS requirements

To install Docker Engine, you need the 64-bit version of one of these Ubuntu versions:

• Ubuntu Hirsute 21.04
• Ubuntu Focal 20.04 (LTS)
• Ubuntu Bionic 18.04 (LTS)

Docker Engine is supported on x86_64 (or amd64 ), armhf , arm64 , and s390x architectures.

Ubuntu 16.04 LTS “Xenial Xerus” end-of-life

Ubuntu Linux 16.04 LTS reached the end of its five-year LTS window on April 30th 2021 and is no longer supported. Docker no longer releases packages for this distribution (including patch- and security releases). Users running Docker on Ubuntu 16.04 are recommended to update their system to a currently supported LTS version of Ubuntu.

Uninstall old versions

Older versions of Docker were called docker , docker.io , or docker-engine . If these are installed, uninstall them:

It’s OK if apt-get reports that none of these packages are installed.

The contents of /var/lib/docker/ , including images, containers, volumes, and networks, are preserved. If you do not need to save your existing data, and want to start with a clean installation, refer to the uninstall Docker Engine section at the bottom of this page.

Supported storage drivers

Docker Engine on Ubuntu supports overlay2 , aufs and btrfs storage drivers.

Docker Engine uses the overlay2 storage driver by default. If you need to use aufs instead, you need to configure it manually. See use the AUFS storage driver

Installation methods

You can install Docker Engine in different ways, depending on your needs:

Most users set up Docker’s repositories and install from them, for ease of installation and upgrade tasks. This is the recommended approach.

Some users download the DEB package and install it manually and manage upgrades completely manually. This is useful in situations such as installing Docker on air-gapped systems with no access to the internet.

In testing and development environments, some users choose to use automated convenience scripts to install Docker.

Install using the repository

Before you install Docker Engine for the first time on a new host machine, you need to set up the Docker repository. Afterward, you can install and update Docker from the repository.

Set up the repository

Update the apt package index and install packages to allow apt to use a repository over HTTPS:

Add Docker’s official GPG key:

Use the following command to set up the stable repository. To add the nightly or test repository, add the word nightly or test (or both) after the word stable in the commands below. Learn about nightly and test channels.

Note: The lsb_release -cs sub-command below returns the name of your Ubuntu distribution, such as xenial . Sometimes, in a distribution like Linux Mint, you might need to change $(lsb_release -cs) to your parent Ubuntu distribution. For example, if you are using Linux Mint Tessa , you could use bionic . Docker does not offer any guarantees on untested and unsupported Ubuntu distributions.

Install Docker Engine

Update the apt package index, and install the latest version of Docker Engine and containerd, or go to the next step to install a specific version:

Got multiple Docker repositories?

If you have multiple Docker repositories enabled, installing or updating without specifying a version in the apt-get install or apt-get update command always installs the highest possible version, which may not be appropriate for your stability needs.

To install a specific version of Docker Engine, list the available versions in the repo, then select and install:

a. List the versions available in your repo:

b. Install a specific version using the version string from the second column, for example, 5:18.09.1

Verify that Docker Engine is installed correctly by running the hello-world image.

This command downloads a test image and runs it in a container. When the container runs, it prints a message and exits.

Docker Engine is installed and running. The docker group is created but no users are added to it. You need to use sudo to run Docker commands. Continue to Linux postinstall to allow non-privileged users to run Docker commands and for other optional configuration steps.

Upgrade Docker Engine

To upgrade Docker Engine, first run sudo apt-get update , then follow the installation instructions, choosing the new version you want to install.

Install from a package

If you cannot use Docker’s repository to install Docker Engine, you can download the .deb file for your release and install it manually. You need to download a new file each time you want to upgrade Docker.

Go to https://download.docker.com/linux/ubuntu/dists/ , choose your Ubuntu version, then browse to pool/stable/ , choose amd64 , armhf , arm64 , or s390x , and download the .deb file for the Docker Engine version you want to install.

To install a nightly or test (pre-release) package, change the word stable in the above URL to nightly or test . Learn about nightly and test channels.

Install Docker Engine, changing the path below to the path where you downloaded the Docker package.

The Docker daemon starts automatically.

Verify that Docker Engine is installed correctly by running the hello-world image.

This command downloads a test image and runs it in a container. When the container runs, it prints a message and exits.

Docker Engine is installed and running. The docker group is created but no users are added to it. You need to use sudo to run Docker commands. Continue to Post-installation steps for Linux to allow non-privileged users to run Docker commands and for other optional configuration steps.

Upgrade Docker Engine

To upgrade Docker Engine, download the newer package file and repeat the installation procedure, pointing to the new file.

Install using the convenience script

Docker provides a convenience script at get.docker.com to install Docker into development environments quickly and non-interactively. The convenience script is not recommended for production environments, but can be used as an example to create a provisioning script that is tailored to your needs. Also refer to the install using the repository steps to learn about installation steps to install using the package repository. The source code for the script is open source, and can be found in the docker-install repository on GitHub.

Always examine scripts downloaded from the internet before running them locally. Before installing, make yourself familiar with potential risks and limitations of the convenience script:

• The script requires root or sudo privileges to run.
• The script attempts to detect your Linux distribution and version and configure your package management system for you, and does not allow you to customize most installation parameters.
• The script installs dependencies and recommendations without asking for confirmation. This may install a large number of packages, depending on the current configuration of your host machine.
• By default, the script installs the latest stable release of Docker, containerd, and runc. When using this script to provision a machine, this may result in unexpected major version upgrades of Docker. Always test (major) upgrades in a test environment before deploying to your production systems.
• The script is not designed to upgrade an existing Docker installation. When using the script to update an existing installation, dependencies may not be updated to the expected version, causing outdated versions to be used.

Tip: preview script steps before running

You can run the script with the DRY_RUN=1 option to learn what steps the script will execute during installation:

This example downloads the script from get.docker.com and runs it to install the latest stable release of Docker on Linux:

Docker is installed. The docker service starts automatically on Debian based distributions. On RPM based distributions, such as CentOS, Fedora, RHEL or SLES, you need to start it manually using the appropriate systemctl or service command. As the message indicates, non-root users cannot run Docker commands by default.

Use Docker as a non-privileged user, or install in rootless mode?

The installation script requires root or sudo privileges to install and use Docker. If you want to grant non-root users access to Docker, refer to the post-installation steps for Linux. Docker can also be installed without root privileges, or configured to run in rootless mode. For instructions on running Docker in rootless mode, refer to run the Docker daemon as a non-root user (rootless mode).

Install pre-releases

Docker also provides a convenience script at test.docker.com to install pre-releases of Docker on Linux. This script is equivalent to the script at get.docker.com , but configures your package manager to enable the “test” channel from our package repository, which includes both stable and pre-releases (beta versions, release-candidates) of Docker. Use this script to get early access to new releases, and to evaluate them in a testing environment before they are released as stable.

To install the latest version of Docker on Linux from the “test” channel, run:

Upgrade Docker after using the convenience script

If you installed Docker using the convenience script, you should upgrade Docker using your package manager directly. There is no advantage to re-running the convenience script, and it can cause issues if it attempts to re-add repositories which have already been added to the host machine.

Uninstall Docker Engine

Uninstall the Docker Engine, CLI, and Containerd packages:

Images, containers, volumes, or customized configuration files on your host are not automatically removed. To delete all images, containers, and volumes:

You must delete any edited configuration files manually.

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