Erlang Cowboy - Dependency crypto is specified as a dependency but is not reachable by the system

Question

I have installed Erlang vesion 19.3 on CentOS 7 linux server. Yesterday, I downloaded Cowboy HTTP server (latest version). In the examples/hello_world directory I have run make (version 4.1) command and got the following error

Dependency crypto is specified as a dependency but is not reachable by the system.

Can anyone help me to resolve the problem?

Answer 1

crypto should be part of your Erlang distribution since it is part of standard library. But if you look closer into documentation you can find that

The current implementation of the Erlang Crypto application is based on the OpenSSL package version 0.9.7 or higher. There are source and binary releases on the web.

Source releases of OpenSSL can be downloaded from the OpenSSL project homepage, or mirror sites listed there.

I would guess that you have those missing. In fact, standard Erlang installation will notify you if binary are missing (package manager might be suppressing those messages)

APPLICATIONS DISABLED (See: ~.kerl/builds/19.3/otp_build_19.3.log)
* crypto         : No usable OpenSSL found
* ssh            : No usable OpenSSL found
* ssl            : No usable OpenSSL found

Just try to install some OpenSSL implementation from your package manager and reinstall Erlang.

As footnote kerl is a good project for managing, testing and fine tuning you VM.