# Add the GPG key curl -s 'https://nobodyinperson.gitlab.io/sshtunnel/gpg.key' | sudo apt-key add - # Add the repository echo 'deb https://nobodyinperson.gitlab.io/sshtunnel/ unstable main' | sudo tee -a /etc/apt/sources.list.d/sshtunnel.list # Update your package cache sudo apt-get update # Install packages from the repository sudo apt-get install sshtunnel