title: New Ubuntu install, trying to install Ruby 2.3.1 alongside 2.5.0 for another project
body: <p>So I've just installed Ubuntu, installed Ruby on Rails (the latest) based on the article here: <a href="https://gorails.com/setup/ubuntu/17.10" rel="nofollow noreferrer">https://gorails.com/setup/ubuntu/17.10</a></p>
  
  <p>I can run rails just fine on a brand new application; however, I'm trying to run an application that requires Ruby 2.3.1. If I go to the rails directory of that application and try to do bundle install, I get:</p>
  
  <p><code>Your Ruby version is 2.5.0, but your Gemfile specified 2.3.1</code></p>
  
  <p>I tried to install Ruby 2.3.1 using <code>rbenv install 2.3.1</code> but I get an error log that looks like a memory stack or something. Nothing that seems to be of any help.</p>
  
  <p>How can I go about installing Ruby 2.3.1 without screwing up my other installation of 2.5.0 since this isn't working? This is the error log I get when trying to install 2.3.1 using rbenv.</p>
  
  <pre><code>~/apps/smartadmin(master*) » rbenv install 2.3.1                                        4:33PM/01.11
  Downloading ruby-2.3.1.tar.bz2...
  -&gt; https://cache.ruby-lang.org/pub/ruby/2.3/ruby-2.3.1.tar.bz2
  Installing ruby-2.3.1...
  
  BUILD FAILED (Ubuntu 17.10 using ruby-build 20171226-3-g01e7b7b)
  
  Inspect or clean up the working tree at /tmp/ruby-build.20180111163349.20841
  Results logged to /tmp/ruby-build.20180111163349.20841.log
  
  Last 10 log lines:
   RAX: 0x0000000000000000 RBX: 0x00005600d84126c0 RCX: 0x0000000200000040
   RDX: 0x00005600d840cf60 RDI: 0x00005600d840cf70 RSI: 0x000000000010dbd0
    R8: 0x00000000ffffffff  R9: 0x00005600d8099000 R10: 0x00005600d8367d40
   R11: 0x00005600d83d1dc8 R12: 0x00005600d840cf70 R13: 0x00005600d79c522a
   R14: 0x00007ffde1bf3fc0 R15: 0x00005600d84126c0 EFL: 0x0000000000010202
  
  -- C level backtrace information -------------------------------------------
  Segmentation fault (core dumped)
  uncommon.mk:654: recipe for target 'enc.mk' failed
  make: *** [enc.mk] Error 139
  </code></pre>
  
  <p>Before I got too ahead of myself and trying to install rvm and using rvm to install 2.3.1, I wanted to get some advice here. I've already had to spin up a fresh VM after getting into a big mess with this.</p>