# Prerequisites

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

* Ubuntu Impish 21.10
* Ubuntu Hirsute 21.04
* Ubuntu Focal 20.04 (LTS)
* Ubuntu Bionic 18.04 (LTS)

### Install Docker Engine

```shell
sudo apt-get update
```

```shell
sudo apt-get install ca-certificates curl gnupg lsb-release -y
```

> Add Docker’s official GPG key:

```shell
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg
```

> Use the following command to set up the stable repository.

```shell
echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu \
  $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
```

> Install Docker Engine

```shell
sudo apt-get update
```

```shell
sudo apt-get install docker-ce docker-ce-cli containerd.io -y
```

### Fix Docker .sock file permission issue

```shell
sudo chmod 666 /var/run/docker.sock
```

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

```shell
sudo docker run hello-world
```

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

## Post-installation steps for Linux

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.

> Create the docker group

```shell
sudo groupadd docker
```

> Add your user to the docker group

```
sudo usermod -aG docker $USER
```

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

```shell
newgrp docker
```

> Verify that you can run docker commands without sudo

```shell
docker run hello-world
```

If you get `/home/user/.docker/config.json: permission denied`

```shell
sudo chown "$USER":"$USER" /home/"$USER"/.docker -R
sudo chmod g+rwx "$HOME/.docker" -R
```

## Configure Docker to start on boot

```shell
sudo systemctl enable docker.service
sudo systemctl enable containerd.service
```

Test the installation

```shell
docker version
```

## Install Docker Compose

Run this command to download the current stable release of Docker Compose

```shell
sudo curl -L "https://github.com/docker/compose/releases/download/1.29.2/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
```

> Please visit Docker website to collect latest version of Docker Compose

[https://docs.docker.com/compose/install](https://docs.docker.com/compose/install/)

Apply executable permissions to the binary

```shell
sudo chmod +x /usr/local/bin/docker-compose
```

> If the command docker-compose fails after installation, check your path. You can also create a symbolic link to /usr/bin or any other directory in your path.

```shell
sudo ln -s /usr/local/bin/docker-compose /usr/bin/docker-compose
```

Optionally, install `command completion` for the `bash` and `zsh` shell.

```shell
sudo curl \
    -L https://raw.githubusercontent.com/docker/compose/1.29.2/contrib/completion/bash/docker-compose \
    -o /etc/bash_completion.d/docker-compose
```

Test the installation

```shell
docker-compose --version
```

> To uninstall Docker Compose

```shell
sudo rm /usr/local/bin/docker-compose
```