Install docker and runner on bare bone Linux 18.04.1 machine

gitlab-runner.sh

#chmod +x gitlab-runners.sh
#Set memory allocation for each runner.
sudo sysctl -w vm.max_map_count=262144


sudo apt install apt-transport-https ca-certificates curl software-properties-common
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 focal stable"
sudo apt update
sudo apt install docker-ce
sudo usermod -aG docker $USER

# Docker-compose
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
sudo chmod +x /usr/local/bin/docker-compose
docker-compose --version

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
echo "In order to register gitlab runners run: sudo gitlab-runner register"


### Troubleshooting###
## If docker-compose gives permission error, first just try plain restart, then below items:

#As second step states. Apply executable permissions to the binary:

sudo chmod +x /usr/local/bin/docker-compose;
#In addition to the comments provided in the question

sudo usermod -aG docker $USER                  # to add myself to docker group
sudo chgrp docker /usr/local/bin/docker-compose     # to give docker-compose to docker group,
sudo chmod 750 /usr/local/bin/docker-compose   # to allow docker group users to execute it
#You might want to try running newgrp docker

sudo usermod -aG docker $USER