How do I fix psych module not being found or being the right version Ruby

Question

I get the following error when trying to do anything with Ruby, specifically ruby gems:

/usr/local/rvm/rubies/ruby-2.4.5/lib/ruby/2.4.0/yaml.rb:5:in `<top (required)>':
It seems your ruby installation is missing psych (for YAML output).
To eliminate this warning, please install libyaml and reinstall your ruby.
/usr/local/rvm/rubies/ruby-2.4.5/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:130:in `require': incompatible library version - /usr/local/rvm/gems/ruby-2.4.5/gems/psych-3.1.0/lib/psych.so (LoadError)
    from /usr/local/rvm/rubies/ruby-2.4.5/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:130:in `rescue in require'
    from /usr/local/rvm/rubies/ruby-2.4.5/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:34:in `require'
    from /usr/local/rvm/gems/ruby-2.4.5/gems/psych-3.1.0/lib/psych.rb:16:in `rescue in <top (required)>'
    from /usr/local/rvm/gems/ruby-2.4.5/gems/psych-3.1.0/lib/psych.rb:13:in `<top (required)>'
    from /usr/local/rvm/rubies/ruby-2.4.5/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:54:in `require'
    from /usr/local/rvm/rubies/ruby-2.4.5/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:54:in `require'
    from /usr/local/rvm/rubies/ruby-2.4.5/lib/ruby/2.4.0/yaml.rb:6:in `<top (required)>'
    from /usr/local/rvm/rubies/ruby-2.4.5/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:54:in `require'
    from /usr/local/rvm/rubies/ruby-2.4.5/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:54:in `require'
    from /usr/local/rvm/rubies/ruby-2.4.5/lib/ruby/site_ruby/2.4.0/rubygems.rb:729:in `load_yaml'
    from /usr/local/rvm/rubies/ruby-2.4.5/lib/ruby/site_ruby/2.4.0/rubygems/config_file.rb:349:in `load_file'
    from /usr/local/rvm/rubies/ruby-2.4.5/lib/ruby/site_ruby/2.4.0/rubygems/config_file.rb:202:in `initialize'
    from /usr/local/rvm/rubies/ruby-2.4.5/lib/ruby/site_ruby/2.4.0/rubygems/gem_runner.rb:79:in `new'
    from /usr/local/rvm/rubies/ruby-2.4.5/lib/ruby/site_ruby/2.4.0/rubygems/gem_runner.rb:79:in `do_configuration'
    from /usr/local/rvm/rubies/ruby-2.4.5/lib/ruby/site_ruby/2.4.0/rubygems/gem_runner.rb:44:in `run'
    from /usr/local/rvm/rubies/ruby-2.4.5/bin/gem:21:in `<main>'

I believe the line of note is this one:

LoadError: incompatible library version - /usr/local/rvm/gems/ruby-2.4.5/gems/psych-3.1.0/lib/psych.so

I get this from gem install puppet , gem update , etc. I tried uninstalling and reinstalling libyaml, and same with Ruby. The error happened after I did bundle uninstall puppet to get it to stop pointing to the 6.3.0 gem and point to the 4.10.2 executable. I need Ruby to be able to use Rspec to test the modules. Does anyone know how I can fix this?

Answer 1

Without steps to reproduce the broken system it is hard to say what happened, but I can say in general how you can set this up correctly to use a specific version of Puppet.

Does this help? In the worst case, you can probably uninstall RVM and reinstall it.

---

Before I continue, let me note that Puppet 4.10.2 and 4.10.3 have both been removed from Rubygems. (Although I was able to install it with PDK.)

For the remainder I assume 4.10.4 instead (just to distinguish it from latest 4.10).

---

The recommended approach is to use Puppet Development Kit (pdk) . If you download and install PDK, you probably just need to do these steps:

pdk convert
rm Gemfile.lock
PUPPET_GEM_VERSION=4.10.4 bundle update # If that version isn't already in PDK.
pdk test unit --puppet-version 4.10.4

---

If you don't want to go down the PDK path, you can try these alternatives:

1. Hardcode the version of Puppet you want in Gemfile.

gem 'puppet', '4.10.4'

Or:

gem 'puppet', '~> 4.10' # latest 4.10

Then update your bundle:

rm -f Gemfile.lock
bundle update

2. Or, you can implement the PUPPET_GEM_VERSION feature by adding this code (this is what I do, for what it's worth):

if puppetversion = ENV['PUPPET_GEM_VERSION']
  gem 'puppet', puppetversion
else
  gem 'puppet'
end

And then:

rm -f Gemfile.lock
PUPPET_GEM_VERSION='~> 4.10' bundle update

Now you can run your unit tests against a specific version of Puppet per normal:

bundle exec rake spec

Or however you set it up.