Morph

This directory contains Nix-based configuration for the grid. This takes the form of Nix expressions in .nix files and some JSON-based configuration in .config.json files.

This configuration is fed to morph to make changes to the deployment.

bootstrap-configuration.nix

This is meant as a minimal system configuration to use as part of crossgrading a Debian install to NixOS. It has a lot of comments explaining different parts of Nix and NixOS. You may want to browse it before looking at other .nix files here.

grid.config.json

This contains configuration for Tahoe-LAFS.

grid.nix

This is the morph entrypoint for the grid. This defines all of the servers that are part of the grid.

The actual configuration is split into separate files that are imported from this one. You can do things like build the network:

morph build grid.nix

<hostname>-hardware.nix

These are the generated hardware-related configuration files for servers in the grid. These files are referenced from the corresponding <hostname>.nix files.

<hostname>-config.nix

Each such file contains a minimal Nix expression supplying critical system configuration details. "Critical" roughly corresponds to anything which must be specified to have a bootable system. These files are referenced by the corresponding <hostname>.nix files.

Configuring New Storage Nodes

Storage nodes are brought into the grid in a multi-step process. Here are the steps to configure a new node, starting from a minimal NixOS 19.03 or 19.09 installation.

1. Copy the remote file /etc/nixos/hardware-configuration.nix to the local file storageNNN-hardware.nix. In the case of an EC2 instance, copy the remote file /etc/nixos/configuration.nix instead.

2. Add "zfs" to boot.supportedFilesystems in storageNNN-hardware.nix.

3. Add a unique value for networking.hostId in storageNNN-hardware.nix.

4. Copy storageNNN-hardware.nix back to /etc/nixos/hardware-configuration.nix.

5. Run nixos-rebuild test.

6. Manually create a storage zpool:

   zpool create -m legacy -o ashift=12 root raidz /dev/disk/by-id/{...}

7. Mount the new ZFS filesystem to verify it is working:

   mkdir /storage
   mount -t zfs root /storage

8. Add a new filesystem entry to storageNNN-hardware.nix:

   # Manually created using:
   #   zpool create -f -m legacy -o ashift=12 root raidz ...
   fileSystems."/storage" = {
     device = "root";
     fsType = "zfs";
   };

9. Create a storageNNN-config.nix containing further configuration for the new host.

10. Add an entry for the new host to grid.nix referencing the new files.

11. Deploy to the new host with morph deploy morph/grid.nix --on <identifier> boot --upload-secrets --reboot.