Installing Docker and Docker Compose

A step-by-step guide to install Docker, Docker Compose and configuring the docker MTU setting

Before Starting

Supported Installation

This installation procedure is tested on Ubuntu 22.04.x LTS and x86_64 architecture.

Installation

To configure the MTU properly, use Docker from apt instead of snap.
If you have already installed Docker through the system installation, remove the snap version of Docker first. Otherwise, skip this step.

Remove snap version of Docker:

sudo snap remove docker

Remove old versions of Docker and Docker Compose Plugin:

for pkg in docker.io docker-doc docker-compose docker-compose-v2 podman-docker containerd runc; do sudo apt remove -y $pkg; done

Remove old versions and install latest version of Docker and Docker Compose Plugin (New Version, Recommended)

wget -qO- https://short.on-cloud.tw/docker-installation-script | sudo bash

Install Docker (Old Version, Not Recommended)

sudo apt install docker.io

You may test the installation by running:
docker --version

Fixing Docker permission error (Otional)

If you encounter a permission error like the following when executing docker commands:

Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get "http://%2Fvar%2Frun%2Fdocker.sock/v1.24/containers/json": dial unix /var/run/docker.sock: connect: permission denied

You can either run docker commands with sudo, or enable a non-root user to access the docker command by following these steps:

Create the docker group on the system:
```
sudo groupadd -f docker
```
Add the active user to the docker group:
```
sudo usermod -aG docker $USER
```
Apply the group changes to the current terminal session:
```
newgrp docker
```
Check if the docker group is in the list of user groups.
```
groups
```
The group should appear in the command output.

You should now be able to issue Docker commands as a non-root user without using sudo.

Install Docker Compose Plugin (Old Version, Not Recommended)

Docker Compose is a tool for defining and running multi-container applications. It appears as a plugin for Docker.
You won't be required to install Docker Compose in order to use Docker, but it is recommended.

Download and install the Compose CLI plugin:

DOCKER_CONFIG=${DOCKER_CONFIG:-$HOME/.docker}
 
mkdir -p $DOCKER_CONFIG/cli-plugins
 
curl -SL https://github.com/docker/compose/releases/latest/download/docker-compose-linux-x86_64 -o $DOCKER_CONFIG/cli-plugins/docker-compose

Apply executable permissions to the binary:

chmod +x $DOCKER_CONFIG/cli-plugins/docker-compose

You may test the installation by running:
docker compose version

Fixing Docker MTU issue (Otional)

To specify/override the MTU for Docker, add a parameter to the Docker launch script. The file to edit is /lib/systemd/system/docker.service.

If you're unsure which is the correct file, you can find it using the following command:

sudo systemctl status docker

Look for the line that starts with Loaded: and find the path after loaded. This is the file you're looking for.

To change the MTU setting (for example, to 1400), modify the line in /lib/systemd/system/docker.service from:

ExecStart=/usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock

to:

ExecStart=/usr/bin/dockerd --mtu 1400 -H fd:// --containerd=/run/containerd/containerd.sock

If you're using docker-compose to launch your instances, you also need to change some configuration to ensure they launch with the specified MTU.

Your Docker Compose file should include the following section:

docker-compose.yml

networks:
  default:
    driver: bridge
    driver_opts:
      com.docker.network.driver.mtu: 1400

After making these changes, restart Docker to apply the new MTU setting:

sudo systemctl daemon-reload
sudo service docker restart

Little tip

Stop all container

If you run into docker start issue, please refer to the following command for solution.

docker stop $(docker ps -a -q)

List the mounted volumes of a container

docker inspect -f '{{ .Mounts }}' [container name/id] | python -m json.tool

Start Docker Daemon

If you run into the error Cannot connect to the Docker daemon. Is 'docker daemon' running on this host? when trying to run Docker commands, you can try restarting the Docker daemon using the following command:

sudo systemctl restart docker