Docker Installation Instructions For Zorin OS 15.2 (Based on Ubuntu 18.04 Bionic Beaver)

Commands come from Syed Komail Abbas' and Brian Hogan's Docker tutorials

Add GPG key for official Docker repo

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

Flags:
-f Fail silently and don't show HTTP errors
-s Don't show progress
-S Show error if curl fails
-L Allow for redirects

Add the Docker Stable repo to a .list file in /etc/apt/sources.list.d/

echo 'deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable' | sudo tee --append /etc/apt/sources.list.d/docker.list

Note:
tee allows for reading from standard input and writing to a file. --append flag wil not overwrite the file if it already exists and will just append to the file.

Doing something like sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable" is also an option, which will add the repo to /etc/apt/sources.list. I like having the repos in individual .list files in case I need to change something or just need to get rid of the repo, so I don't have to go in the sources.list file to look for the specific repo.

Update your package database to pull in the new Docker repo and make sure there are no errors

sudo apt update

Ensure you're installing from the Docker repo and not Ubuntu default repo

apt-cache policy docker-ce

Output will look something like the below:

docker-ce:
  Installed: (none)
  Candidate: 18.03.1~ce~3-0~ubuntu
  Version table:
     18.03.1~ce~3-0~ubuntu 500
        500 https://download.docker.com/linux/ubuntu bionic/stable amd64 Packages

Install Docker Community Edition

sudo apt install -y docker-ce

Check Docker staus And make sure it's running

sudo systemctl status docker

Output:

● docker.service - Docker Application Container Engine
   Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: 
   Active: active (running) since Fri 2020-05-03 17:43:31 PDT; 11min ago
     Docs: https://docs.docker.com
 Main PID: 8324 (dockerd)
    Tasks: 12
   Memory: 40.3M
   CGroup: /system.slice/docker.service
           └─8324 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/contai

May 31 17:43:31 <youruser> dockerd[8324]: time="2020-05-03T17:43:31.366671980-07:00
May 31 17:43:31 <youruser> dockerd[8324]: time="2020-05-03T17:43:31.366682440-07:00
May 31 17:43:31 <youruser> dockerd[8324]: time="2020-05-03T17:43:31.367023487-07:00
May 31 17:43:31 <youruser> dockerd[8324]: time="2020-05-03T17:43:31.368620032-07:00
May 31 17:43:31 <youruser> dockerd[8324]: time="2020-05-03T17:43:31.529253221-07:00
May 31 17:43:31 <youruser> dockerd[8324]: time="2020-05-03T17:43:31.655852930-07:00
May 31 17:43:31 <youruser> dockerd[8324]: time="2020-05-03T17:43:31.797542770-07:00
May 31 17:43:31 <youruser> dockerd[8324]: time="2020-05-03T17:43:31.797631727-07:00
May 31 17:43:31 <youruser> systemd[1]: Started Docker Application Container Engine.
May 31 17:43:31 <youruser> dockerd[8324]: time="2020-05-03T17:43:31.821129140-07:00

Add your user to the Docker group to avoid having to use sudo each time with Docker

sudo usermod -aG docker ${USER}

Confirm that your user is part of the Docker group. May need to logout or reboot

id -nG

Flags:
-n Print a name instead of a number
-G Print the group IDs

Output:
<youruser> adm sudo docker

Pull down Geographica's Postgres/PostGIS Docker image. At the time this image was using PostgreSQL 12.2 PostGIS 3.0.1 GEOS 3.8.0, PROJ 6.3.1.

docker pull geographica/postgis

Check and make sure the above is in your Docker images

docker images list

Create a data directory for your container so the data is persistent (othewise data is lost once the container is shutdown)

mkdir -p $HOME/docker/volumes/postgres

Flags:
-p Will create directory if it doesn't exist and won't complain with errors (even if it does already exist)

Startup the new Docker container from your downloaded image

docker run --rm --name <name for your container> -e POSTGRES_PASSWORD=<password> -d -p 5432:5432 -v $HOME/docker/volumes/postgres:/var/lib/postgresql/data geographica/postgis:latest

You can also add this command to an alias in your .bashrc file so you don't have to remember this insanely long command each time you want to run you container. Would be something like alias pg-docker='docker run --rm --name <name for your container> -e POSTGRES_PASSWORD=<password> -d -p 5432:5432 -v $HOME/docker/volumes/postgres:/var/lib/postgresql/data geographica/postgis:latest

Flags:
--rm Removes the container and its file system once container has been shutdown. It's generally regarded as good practice to pass this flag and if data needs to be persisten the --v flag can be passed.
--name Name you would like for the container to identify it.
--e Expose the POSTGRES_PASSWORD varible so we can set a a password for the DB.
-d Launch the container in the background.
-p Bind port on local host to port in container. So in this instance port 5432 on local host is bound to 5432 of the container. Port 5432 should be available on your local host but may not be if you're already running a PostgreSQL instance. You can use something like -p 5433:5432 if this is the case.
-v Mount the newly created $HOME/docker/volumes/postgres dir to the /var/lib/postgresql/data dir of the container so the data is persistent.

A docker compose file can also be used instead of using the above command or adding it to an alias

• Install docker-compose with sudo apt install docker-compose if not already installed
• Create a docker-compose.yml file with the text below

version: "3.2"
services:
    gisdata:
     image: geographica/postgis
     ports:
      - "5432:5432"
     volumes:
      - type: bind
        source: $HOME/docker/volumes/postgres
        target: /var/lib/postgresql/data
     environment:
        POSTGRES_PASSWORD: '<password>'

• Run docker-compose up -d within the directory where the compose file is located to start the container

Determine IP of your container so you can connect to it with pgAdmin or something like DBeaver. Depends on your preference if you want a stand-alone desktop application (DBeaver) or one that lanuches in a browser (pgAdmin)

docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' pg-docker

Launch your preferred DB tool to connect with and connect to your database with the IP from above.