Set up and use a network of local development VMs

... using Vagrant to manage VirtualBox VMs. (The author of this documentation wasted a lot of time trying to get Vagrant to work with KVM/libvirt. Issues with networking that looked like guest misconfigurations vanished after changing to the better-tested combination of Vagrant and VirtualBox.)

This requires NixOS. Nix without the OS will not work.

Use the local development environment

0. Add VirtualBox to your NixOs system configuration at /etc/nixos/configuration.nix:

   virtualisation.virtualbox.host.enable = true;
   # Save bytes and build time, optional but recommended:
   virtualisation.virtualbox.host.headless = true;

1. Enter the morph local grid directory:

   cd morph/grid/local

2. Enter the project's nix-shell:

   nix-shell ../../../shell.nix

3. Build and start the VMs:

   VAGRANT_DEFAULT_PROVIDER=virtualbox vagrant up

4. Then, add the Vagrant SSH configuration to your user's ~/.ssh/config file:

   install -d ~/.ssh ; vagrant ssh-config >> ~/.ssh/config

Latest Morph honors the SSH_CONFIG_FILE environment variable (since 3f90aa88 (March 2020, v 1.5.0)), so in the future this should get a bit more convenient.

6. Create a public-keys/users.nix file with your SSH key (see public-keys/users.nix.example for the format) so you'll be able to log in after deploying the new configuration:

   $EDITOR public-keys/users.nix

7. Then, build and deploy our software to the Vagrant VMs:

   morph build grid.nix
   morph push grid.nix
   morph deploy grid.nix boot
   vagrant halt
   vagrant up
   morph upload-secrets grid.nix

You should now be able to log in with the users and keys you set in your users.nix file.