Package unikernels as containers for urunc with Nix

This repository contains all the necessary files to package unikernels as container images that can be deployed in urunc.

Requirements

Since the packaging take place with Nix, we need to install Nix package manger or run it NixOS. For up-to-date instructions on installing Nix package manger, please check here. According to that page, a (recommended) multi-user installation can take place with the following command.

sh <(curl -L https://nixos.org/nix/install) --daemon

Usage guide

After installing Nix packages, a user can package urunc containers simply with:

nix-build default.nix

The above command will create a Docker image tar using the information in args.nix file. In particular, the args.nix file has the following fields:

• name: The name of the final container image
• tag: The tag of the final container image
• files: A list of local files to copy inside the container's rootFS. Every entry has a key, which is the path to the local file (relative to CWD) and a value, which is the path inside the container rootfs, where the file will be placed.
• annotations: A list of all annotations that urunc supports.

For exmaple the default content of args.nix is the following one:

{
  name = "hello-rumprun";
  tag = "latest";
  files = {
    "./hello1.hvt" = "/unikernel/hello.hvt";
  };
  annotations = {
    unikernelType = "rumprun";
    hypervisor = "hvt";
    binary = "/unikernel/hello.hvt";
    cmdline = "hello";
    unikernelVersion = "";
    initrd = "";
    block = "";
    blkMntPoint = "";
  };
}

Therefore, the Nix build will:

1. Copy the file hello.hvt in CWD inside container;s rootfs under /unikernel/hello.hvt.
2. Setup the urunc annotations, creating a urunc.json file inside the container rootfs.
3. It will name the final container image after the hello-rumprun name and it will tag it with the tag latest.

When running nix-build the output will be a Docker image tar file in the Nix store. Nix by default, wil lalso create a symlink, called result in our CWD poinitng to the respctive path in the Nix store.

We can load the Docker image with:

docker load < result