Using a non-NixOS distro as a nixos-container host

1. Install Nix in multi-user mode (https://nixos.org/nix/manual/#sect-multi-user-installation)

2. Install required packages for systemd-nspawn

e.g. on debian: apt install systemd-container

3. As root install container-system

nix-env -iE 'f: import "${builtins.fetchGit http://github.com/corngood/portable-nixos-container.git}/container-system.nix"'

4. Symlink systemd units into host system

ln -s ~/.nix-profile/etc/systemd/system/{nat,container@}.service /etc/systemd/system
systemctl daemon-reload

5. Start and enable nat service (required for containers to have network access)

systemctl start nat
mkdir -p /etc/systemd/system/network.target.wants
ln -s ~/.nix-profile/etc/systemd/system/nat.service /etc/systemd/system/network.target.wants

6. Create containers using nixos-container or by deploying with nixops

7. Permanently enable a container

ln -s /etc/systemd/system/container@.service /etc/systemd/system/multi-user.target.wants/container@[container-name].service

8. Expose ports

Edit /etc/containers/[container-name].conf and add to HOST_PORT. Each word will correspond to the value of a systemd-nspawn --port argument.

You must restart the container for configuration changes to have an effect systemctl restart container@[container-name].

WARNING these ports may not be forwarded from the loopback interface.

9. Configure systemd-nspawn

Edit /etc/containers/[container-name].conf and add EXTRA_NSPAWN_FLAGS. This variable will be appended to the nspawn arguments, and can contain anything from man systemd-nspawn.

e.g. to create a bind mount: --bind=/mnt/container/var:/var

systemd-nspawn may also be configured using /etc/systemd/nspawn/[container-name].nspawn according to the manual.