I hope this will prove useful for other readers of the book.

I was working through chapter 20 OTP: Applications and run to issues with the example for creating a release using Distillery.

The command mix release --env=prod failed with an error like

** (Mix) Could not invoke task “release”: 1 error found!
–env : Unknown option

Since Elixir 1.9 brings releases directly into Elixir, the mix release -command previously used with distillery now overlaps with the Elixir release command.
Distillery version 2.1 works with Elixir 1.9 and updates the distillery release command to mix distillery.release.

I made the following changes to be able to locally follow the distillery release example in the book.

Elixir and OTP versions used:

$ elixir --version
Erlang/OTP 23 [erts-11.0.2] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [hipe]

Elixir 1.10.4 (compiled with Erlang/OTP 22)

I don’t have relevant pages as my kindle only shows “locations”, but I have included the section topics.

Section “Your First Release”

1 Change dependency to distillery 2.1 in mix.exs
{:distillery, “~> 1.5”, runtime: false}
{:distillery, “~> 2.1”, runtime: false}

2 Use the updated command for initializing the release
mix release.init
mix distillery.init

3 Create the first release (0.0.1)
mix release --env=prod
MIX_ENV=prod mix distillery.release --env=prod

This first failed for me (after following the book example) with

Release failed: could not load /path/config/config.exs

I got around it by adding a minimal config.exs file
mkdir config && echo “import Config” > config/config.exs

Side note:
In the book the deploy commands are run with ssh.
I tried, instead, to run the deploy commands directly from the _build -directory and found out that consecutive releases don’t work properly that way.

“I only just noticed that the original issue confirms that this issue was occurring because of running from _build.”
Successive hot upgrade releases produce error · Issue #160 · bitwalker/distillery · GitHub

This might be documented on the distillery documentation, but I haven’t made it there yet.

Section “A Second Release”

4 Create the first upgrade release (0.2.0)
mix release --env=prod --upgrade
MIX_ENV=prod mix distillery.release --env=prod --upgrade

5 Upgrade running code
This might be because I didn’t use ssh, but instead just copied the archives to separate directory,
but the command deploy/bin/sequence upgrade 0.2.0 failed with

Node user@host is not running!

To successfully run the upgrade I changed the following:
Update node name, -name argument, in rel/vm.args with the right node name. You can check the node name in the iex console with Node.self command.
Not sure if relevant, but I updated the set cookie option (environment :prod) in rel/config.exs with the value in ~/.erlang.cookie

Section “Migrating Server State”
6. Create the second release
mix release --env=prod --upgrade
MIX_ENV=prod mix distillery.release --env=prod --upgrade

That did it for me