Nerves

v1.0.0-rc.0

Nerves

Updating Projects

Please review this guide before updating your projects. Help is available via the #nerves channel on the elixir-lang slack and the Elixir forum.

Contents:

Updating from v0.8 to v0.9

Nerves v0.9.0 contains changes that require updates to existing projects. All users are highly encouraged to update, but if you cannot, be sure to force the Nerves version in your mix.exs dependencies.

Update Nerves Bootstrap to v0.8.1

Nerves Bootstrap is an Elixir archive that provides a new project generator and some logic required for the Nerves integration into mix. Nerves v0.9 requires updates to this archive.

Install the latest Nerves Bootstrap archive by running:

mix local.nerves

or

mix archive.install hex nerves_bootstrap

Update mix.exs aliases (old)

IMPORTANT: If you’re upgrading to Nerves v1.0, this step has been superceded.

Nerves requires that you add aliases to your project’s mix.exs to pull in the firmware creation and crosscompilation logic. Previously, you needed to know which aliases to override. Nerves v0.9 added a new alias. Rather than add this alias, we recommend using the new alias helper in your mix.exs. To do this, edit the target aliases function to look like this:

defp aliases(_target) do
  [
    # Add custom mix aliases here
  ]
  |> Nerves.Bootstrap.add_aliases()
end

This only works with nerves_bootstrap v0.7.0 and later, so if you get an error, be sure to update your Nerves Bootstrap as described in the previous section.

For those interested in more details, the reason behind this change was to move precompiled artifact downloads from the mix compile step to the mix deps.get step. That entailed adding additional logic to the deps.get step and hence an additional alias.

Replace Bootloader with Shoehorn

During this release, we renamed one of our dependencies from bootloader to shoehorn to prevent overloading the term bootloader in the embedded space. This requires a few updates:

First, update the dependency by changing:

{:bootloader, "~> 0.1"}

to

{:shoehorn, "~> 0.2"}

Next, update the distillery release config in rel/config.exs. Look for the line near the end that looks like:

plugin Bootloader.Plugin

or

plugin Bootloader

and change it to

plugin Shoehorn

Finally, change references to bootloader in your config/config.exs to shoehorn. For example, change:

config :bootloader,
  init: [:nerves_runtime],
  app: :my_app

to

config :shoehorn,
  init: [:nerves_runtime],
  app: :my_app

Artifact checksums

Some Nerves dependencies reference a large precompiled version of their build products to significantly reduce compilation time. These are called artifacts and due to their size, they cannot be hosted on hex.pm. Nerves downloads these automatically as part of the dependency resolution process. It is critical that they match the corresponding source code and the previous method of checking version numbers was insufficient. Nerves v0.9.0 now uses a checksum of the projects source files. This works for all projects no matter what version control system they use or how they are stored.

If you have created a custom Nerves system or toolchain, you will need to update your project’s mix.exs to ensure that the checksum covers the right files. This is done using the :checksum key on the nerves_package. Since the files that you checksum are likely identical to those published on hex.pm, we recommend creating a package_files/0 function that’s used by both.

Here’s an example from nerves-project/nerves_system_rpi0:

  def nerves_package do
    [
      # ... Other Options
      checksum: package_files()
    ]
  end

  defp package do
    [
      maintainers: ["Timothy Mecklem", "Frank Hunleth"],
      files: package_files(),
      licenses: ["Apache 2.0"],
      links: %{"Github" => "https://github.com/nerves-project/#{@app}"}
    ]
  end

  defp package_files do
    [
      "LICENSE",
      "mix.exs",
      "nerves_defconfig",
      "README.md",
      "VERSION",
      "rootfs_overlay",
      "fwup.conf",
      "fwup-revert.conf",
      "post-createfs.sh",
      "post-build.sh",
      "cmdline.txt",
      "linux-4.4.defconfig",
      "config.txt"
    ]
  end

Easier artifact creation

Prior to Nerves v0.9.0, creating artifacts for Nerves systems and toolchains required manual steps. Nerves v0.9.0 adds the nerves.artifact mix task to make this easier. Please update your CI scripts or build instructions to use this new method.

Nerves makes it easier to predigest artifacts for systems and toolchains with the added mix task mix nerves.artifact <app_name> Ommitting <app_name> will default to the app name of the parent mix project. This is useful if you are calling mix nerves.artifact from within a custom system or toolchain project.

For example, lets say we have a custom rpi0 system and we would like to create an artifact. mix nerves.artifact custom_system_rpi0

This will produce a file in the current working directory with a name of the format <app_name>-<host_tuple | portable>-<version>-<checksum><extension>

For example, custom_system_rpi0-portable-0.11.0-17C58821DE265AC241F28A0A722DB25C447A7B5FFF5648E4D0B99EF72EB3341F.tar.gz

Artifact sites

Once you’ve created the artifact (or had CI create it for you), you can then upload this to Github releases and instruct the artifact resolver to fetch this artifact following deps.get. Update the Nerves package config by editing the :nerves_package options of Mix.project/0 for your custom system or toolchain to set the sites for which the artifact is available on.

This can be passed as {:github_releases, "<orginization>/<repository>"} or specified as url / path prefixes {:prefix, "/path/to/artifact_dir"} {:prefix, http://artifact_server.com/artifacts}

def nerves_package do
  [
    # ... Other Options
    artifact_sites: [
      {:github_releases, "nerves-project/custom_system_rpi0"}
    ]
  ]
end

The artifact resolver will attempt to fetch from each site listed until it successfully retreives an artifact or it reaches the end of the list.

Updating from v0.9 to v1.0.0-rc.0

Update to Nerves Bootstrap v1.0.0-rc.0

Nerves Bootstrap is an Elixir archive that provides a new project generator and some logic required for the Nerves integration into mix. Nerves v1.0-rc requires updates to this archive.

Install the latest Nerves Bootstrap archive by running:

mix local.nerves

or

mix archive.install hex nerves_bootstrap

Update project dependencies

You will need to update the version string for nerves and nerves_bootstrap in your projects to enable the usage of 1.0-rc. Open your mix.exs file and start by updating the nerves_bootstrap archive:

  # mix.exs

  def project do
    [
      # ...
      archives: [{:nerves_bootstrap, "~> 1.0-rc"}],
    ]
  end

Then update the nerves dep:


  # Run "mix help deps" to learn about dependencies.
  defp deps do
    [{:nerves, "~> 1.0-rc", runtime: false}] ++ deps(@target)
  end

You may have to set override: true if you are using other Nerves packages that have not been updated to depend on Nerves 1.0-rc yet

If you wish to revert, you lock to a specific version using ~> 0.8.0 or = 0.8.0

Update mix.exs aliases

nerves_bootstrap 1.0-rc manages its own aliases on Application.start/1 and is invoked by setting MIX_TARGET to value other then host. Update your mix.exs file to add the bootstrap/1 function and change the aliases to [loadconfig: [&bootstrap/1]]:


  # mix.exs

  def project do
    [
      # ...
      aliases: [loadconfig: [&bootstrap/1]],
    ]
  end

  # Starting nerves_bootstrap pulls in the Nerves hooks to mix, but only
  # if the MIX_TARGET environment variable is set.
  defp bootstrap(args) do
    Application.start(:nerves_bootstrap)
    Mix.Task.run("loadconfig", args)
  end