Install Docker + Docker-compose on Ubuntu

setup_ubuntu_instance.sh

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
sudo apt-get update
apt-cache policy docker-ce
sudo apt-get install -y docker-ce
sudo curl -o /usr/local/bin/docker-compose -L "https://github.com/docker/compose/releases/download/1.21.2/docker-compose-$(uname -s)-$(uname -m)"
sudo chmod +x /usr/local/bin/docker-compose

sudo usermod -a -G docker $USER
# reenter ssh

Install gitlab ci runner

https://about.gitlab.com/2016/04/19/how-to-set-up-gitlab-runner-on-digitalocean/

curl -L https://packages.gitlab.com/install/repositories/runner/gitlab-runner/script.deb.sh | sudo bash
sudo apt-get install gitlab-runner
gitlab-runner --version

# goto project settings -> runners
sudo gitlab-runner register

# if docker executor
sudo usermod -a -G docker gitlab-runner 

# if dind
sudo vim /etc/gitlab-runner/config.toml # to add priviliged flag (https://gitlab.com/gitlab-org/gitlab-runner/issues/1544#note_13439656) 
sudo gitlab-runner restart

# in case "New runner. Has not connected yet"
# https://codereviewvideos.com/blog/how-i-solved-new-runner-has-not-connected-yet-in-gitlab-ci/#comment-5803
sudo chown -R gitlab-runner:gitlab-runner /home/gitlab-runner
sudo systemctl restart gitlab-runner.service

sudo apt-get install git-crypt

https://askubuntu.com/a/833979/696966

sudo nvim /etc/sysctl.conf
sudo sysctl -p
fs.inotify.max_user_watches=1048576