# Docker

Information on how to install and use Docker.

Docker is an open-source project that automates the deployment of applications inside software containers.

## Prerequisites

Ensure you have the following:

- a (fresh) install of Ubuntu LTS with SSH enabled and VSCode installed including a `sudo` user

  >- SSH: `sudo apt install openssh-server`
  >- VSCode: download `.deb` package from [this URL](https://code.visualstudio.com/download)

- OR a Windows machine including a `Administrator` user with VSCode installed

  >- VSCode: download `Windows installer` package from [this URL](https://code.visualstudio.com/download)

## Install Docker on Ubuntu

### Step 1 - Installing Docker

Add the `docker-ce` repo:

```bash
sudo apt update
sudo apt install apt-transport-https ca-certificates curl software-properties-common gnupg lsb-release

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

sudo apt update
```

Install `docker`:

```bash
sudo apt install docker-ce
```

### Step 2 - Executing the Docker Command Without Sudo

```bash
sudo usermod -aG docker ${USER}
```

Reboot your machine:

```bash
sudo reboot
```

### Step 3 - Installing docker-compose

`Docker Compose` is a tool that allows you to run multi-container application environments based on definitions set in a YAML file. It uses service definitions to build fully customizable environments with multiple containers that can share networks and data volumes.

```bash
mkdir -p ~/.docker/cli-plugins/
curl -SL https://github.com/docker/compose/releases/download/v2.3.3/docker-compose-linux-x86_64 -o ~/.docker/cli-plugins/docker-compose

chmod +x ~/.docker/cli-plugins/docker-compose
```

To verify that the installation was successful, you can run:

```bash
docker compose version
```

You'll see output similar to this:

```bash
Docker Compose version v2.3.3
```

## Setting Up a `docker-compose.yml` file

To demonstrate how to set up a `docker-compose.yml` file and work with `Docker Compose`, you'll create a **postgres** environment using the official `postgres` image from `Docker Hub`, the public **Docker registry**. This containerized environment will serve a `postgres` service.

Start off by creating a new directory in your home folder, and then moving into it:

```bash
mkdir ~/docker-repo
cd ~/docker-repo
```

In this directory, set up an application folder to serve as the document root for your **postgres** environment and an *running* folder to serve as **persistent** "rundir" root:

```bash
mkdir postgres
mkdir runnning
```

Next, create the `docker-compose.yml` file:

```bash
vi docker-compose.yml
```

Insert the following content in your `docker-compose.yml` file:

```yaml
version: '3.7'

services:
  postgres:
    image: postgres:11
    container_name: postgres
    network_mode: bridge
    restart: always
    ports:
      - 5432:5432
    environment:
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=my_password
    volumes:
      - /home/$USER/docker-repo/running/postgres/data:/var/lib/postgresql/data
```

Save and close the file.

## Running docker-compose

With the `docker-compose.yml` file in place, you can now execute `Docker Compose` to bring your environment up. The following command will download the necessary `Docker` images, create a container for the **postgres** service, and run the containerized environment in background mode:

```bash
docker-compose -f docker-compose.yml up -d
```

`Docker Compose` will first look for the defined image on your local system, and if it can't locate the image it will download the image from `Docker Hub`.

Your environment is now up and running in the background. To verify that the container is active, you can run:

```bash
docker ps
```

## Usefull commands

Go inside the container:

```bash
docker exec -it postgres /bin/bash -l
```

Stop, start or restart the container:

```bash
docker stop postgres
docker start postgres
docker restart postgres
```

> Tips for Daniele

```bash
docker exec -it postgres /bin/bash -l
apt update
apt install postgis
exit
```

> Tips for Daniele (Configure a database and dump the content from `dbexport.pgsql`)

```bash
psql -h localhost -p 5432 -U postgres

CREATE ROLE livestock WITH SUPERUSER CREATEDB CREATEROLE LOGIN ENCRYPTED PASSWORD 'happycattle';
CREATE DATABASE livestock_db;
GRANT ALL PRIVILEGES ON DATABASE livestock_db TO livestock;
\q

psql -h localhost -p 5432 -U livestock livestock_db

CREATE SCHEMA postgis;
CREATE EXTENSION postgis SCHEMA public;
\q

psql -h localhost -p 5432 -U livestock livestock_db < dbexport.pgsql

psql -h localhost -p 5432 -U livestock livestock_db

SELECT * FROM livpop ORDER BY livpop DESC LIMIT 10;
\q
```

## Install Docker on Windows

### Install interactively

- Downloaded the installer (`Docker Desktop Installer.exe`) from [Docker Hub](https://docs.docker.com/desktop/install/windows-install/)
- Double-click `Docker Desktop Installer.exe` to run the installer
- When prompted, ensure the **Use WSL 2** instead of **Hyper-V** option on the *Configuration page* is selected or not depending on your choice of backend
  > If your system only supports one of the two options, you will not be able to select which backend to use
- Follow the instructions on the installation wizard to authorize the installer and proceed with the install
- When the installation is successful, click *Close* to complete the installation process

### Start Docker Desktop

Docker Desktop does not start automatically after installation. To start Docker Desktop:

- Search for Docker, and select `Docker Desktop` in the search results
- The Docker menu displays the *Docker Subscription Service Agreement* window.
- Select *Accept* to continue. `Docker Desktop` starts after you accept the terms