Error installing ffi gem

If you have problems installing a gem and get a error collect2: error: ld returned 1 exit status it's due to missing development headers of a library (ld is the linker).

For example, with this output:

$ gem install json
Building native ...

When you get this while installing the raspell gem:

ERROR:  Error installing raspell:  
ERROR: Failed to build gem native extension.

You need some libraries:

sudo apt-get install libaspell-dev

You're better off using debugger-ruby_core_source:

gem install debugger-ruby_core_source

If you can't do this, try the following.

Here is how to fix the following error when installing the debugger gem fails:

Gem::Instal...

Recent Bundler (1.16.1) started complaining about missing dependencies in the Gemfile. This is due to a stricter handling of specifications (see attached link).

The error message looks like this:

Downloading example-gem-1.2.3 revealed depend...

So you're getting an error like this:

undefined method `activate_bin_path' for Gem:Module (NoMethodError)

Here is what happened:

• You installed a recent version of Rubygems
• You installed some gems that install a binary (like `bun...

If you get an error like this:

An error occurred while installing pg (0.17.1), and Bundler cannot continue.
Make sure that gem install pg -v '0.17.1' succeeds before bundling.

Then do this:

sudo apt-get install libpq-dev

... an...

So you got this error, even though your Gemfile bundles mysql2:

!!! Missing the mysql2 gem. Add it to your Gemfile: gem 'mysql2'

or

Please install the mysql adapter: `gem install activerecord-mysql-adapter` (mysql is not par...

You are probably using Ruby 1.8.7 with a too recent versions of Rubygems.

Downgrade your Rubygems to the latest version that works with 1.8.7.

See also

• [Fix Rubygems warning: Gem.source_index is deprecated, use Specifica...

When Rack::Bug has been added to your project and your Apache2/Passenger only replies with an Error 500 (Internal Server Error) you won't get any love from both application and Apache logs.

You can start a script/server and try connecting t...

You can download .gem files using gem fetch:

gem fetch activesupport consul

This will produce files like active-support-5.0.0.gem and consul-0.12.1.gem in your working directory.

Dependencies will not be downloaded.