Packer

Packer is a tool for creating identical machine images for multiple platforms from a single source configuration.

Using Packer with plugins

Packer's functionality is extended through plugins. Rather than letting Packer download plugins at runtime, you can build a Packer wrapper that bundles the plugins you need with packer.withPlugins.

packer.withPlugins takes a function that receives the set of available plugins and returns the list of plugins to include:

packer.withPlugins (ps: [ ps.docker ])

This produces a packer executable wrapped with the PACKER_PLUGIN_PATH environment variable set, so the selected plugins are available without a separate packer plugins install step.

For example, to get a development shell with Packer and the Docker plugin:

{
  pkgs ? import <nixpkgs> { },
}:

pkgs.mkShell {
  packages = [
    (pkgs.packer.withPlugins (ps: [ ps.docker ]))
  ];
}

Multiple plugins can be selected at once:

packer.withPlugins (ps: [
  ps.docker
  ps.qemu
])

Listing available plugins

The packaged plugins are exposed as the packer.plugins attribute set. To list every plugin available in your version of Nixpkgs, query its attribute names:

$ nix eval nixpkgs#packer.plugins --apply builtins.attrNames
[ "docker" "qemu" ]

Without flakes:

$ nix-env -f '<nixpkgs>' -qaP -A packer.plugins
packer.plugins.docker  packer-plugin-docker-1.1.2
packer.plugins.qemu    packer-plugin-qemu-1.1.4

The attribute name (for example docker or qemu) is what you pass to packer.withPlugins.

Notes:

• mkPackerPlugin currently only supports fetchFromGitHub as the fetcher.

nixos.org/manual/nixpkgs/stable/packages/packer.html