Mention required Ruby version

doc/install/installation.md

@@ -107,9 +107,16 @@ Then select 'Internet Site' and press enter to confirm the hostname.
 
 ## 2. Ruby
 
-The use of Ruby version managers such as [RVM](https://rvm.io/), [rbenv](https://github.com/sstephenson/rbenv) or [chruby](https://github.com/postmodern/chruby) with GitLab in production frequently leads to hard to diagnose problems. For example, GitLab Shell is called from OpenSSH and having a version manager can prevent pushing and pulling over SSH. Version managers are not supported and we strongly advise everyone to follow the instructions below to use a system Ruby.
+_**Note:** The current supported Ruby versions are 2.1.x. Ruby 2.2 and 2.3 are
+currently not supported._
 
-Remove the old Ruby 1.8 if present
+The use of Ruby version managers such as [RVM], [rbenv] or [chruby] with GitLab
+in production, frequently leads to hard to diagnose problems. For example,
+GitLab Shell is called from OpenSSH, and having a version manager can prevent
+pushing and pulling over SSH. Version managers are not supported and we strongly
+advise everyone to follow the instructions below to use a system Ruby.
+
+Remove the old Ruby 1.8 if present:
 
     sudo apt-get remove ruby1.8
 
@@ -555,3 +562,7 @@ this is likely due to an outdated Nginx or Apache configuration, or a missing or
 misconfigured gitlab-workhorse instance. Double-check that you've
 [installed Go](#3-go), [installed gitlab-workhorse](#install-gitlab-workhorse),
 and correctly [configured Nginx](#site-configuration).
+
+[RVM]: https://rvm.io/ "RVM Homepage"
+[rbenv]: https://github.com/sstephenson/rbenv "rbenv on GitHub"
+[chruby]: https://github.com/postmodern/chruby "chruby on GitHub"

doc/install/requirements.md

@@ -32,9 +32,12 @@ Please consider using a virtual machine to run GitLab.
 
 ## Ruby versions
 
-GitLab requires Ruby (MRI) 2.1
+GitLab requires Ruby (MRI) 2.1.x and currently does not work with versions 2.2
+and 2.3.
+
 You will have to use the standard MRI implementation of Ruby.
-We love [JRuby](http://jruby.org/) and [Rubinius](http://rubini.us/) but GitLab needs several Gems that have native extensions.
+We love [JRuby](http://jruby.org/) and [Rubinius](http://rubini.us/) but GitLab
+needs several Gems that have native extensions.
 
 ## Hardware requirements