# Setting up Docker and Docker Compose

> A step by step tutorial to setup Docker and Docker Compose on Linux systems

Source: https://last9.io/docs/setting-up-docker-and-docker-compose-on-linux/

This document describes the steps for setting up `docker` and `docker-compose`
on a Linux system. It supports Ubuntu and CentOS-like flavours.

Create a file `/var/tmp/init-docker.sh` with the following contents:

```shell
#!/bin/bash

set -e

# Install docker
echo
echo "=========================="
echo "STATUS: docker"
echo "=========================="
# Can do command -v but better to be specific
if [[ -f '/usr/bin/docker' ]]; then
    echo "STATUS: docker: installed"
else
    echo "STATUS: docker: installing"
    set -ex
    curl -fsSL https://get.docker.com/ | sh -x
    command -v docker > /dev/null
    set +ex
    sudo groupadd docker
    sudo usermod -aG docker "$USER"
    echo "STATUS: docker: installed"
    newgrp -
fi

# Install docker-compose
echo
echo "=========================="
echo "STATUS: docker-compose"
echo "=========================="
# Can do command -v but better to be specific
if [[ -f '/usr/local/bin/docker-compose' ]]; then
    echo "STATUS: docker-compose: installed"
else
    echo "STATUS: docker-compose: installing"
    set -ex
    sudo curl -L \
       "https://github.com/docker/compose/releases/download/2.23.3/docker-compose-$(uname -s)-$(uname -m)" \
       -o /usr/local/bin/docker-compose
    sudo chmod +x /usr/local/bin/docker-compose
    command -v docker-compose > /dev/null
    set +ex
    echo "STATUS: docker-compose: installed"
fi
```

Run this file as a non-root user who can have `sudo` privileges

```shell
./init-docker.sh
```

Enable docker to run at startup

For Ubuntu:

```shell
systemctl --user enable docker
```

For Centos / Amazon Linux

```shell
sudo service docker start
sudo chkconfig docker on
```

## Optional hardening steps

- Allow Docker processes to be long-running and not get terminated on
  User-shell logout
  Users cannot set user services to run at boot time by default. The admin must
  enable this on an individual basis for each user. From the
  [documentation](https://www.freedesktop.org/software/systemd/man/loginctl.html):

  > Enable/disable user lingering for one or more users. If enabled for
  > a specific user, a user manager is spawned for the user at boot and
  > kept around after logouts. This allows users who are not logged in to
  > run long-running services. Takes one or more user names or numeric UIDs
  > as argument. If no argument is specified, enables/disables lingering for
  > the user of the session of the caller.

  ```shell
  sudo loginctl enable-linger $(whoami)
  ```

- Prevent Docker daemon crashes to terminate the processes. By default, when the Docker daemon terminates, it shuts down running containers. You can configure the daemon so that containers remain running if the daemon becomes unavailable. This functionality is called live restore. The live restore option helps reduce container downtime due to daemon crashes, planned outages, or upgrades