One of the most confusing things about learning rails is in dealing with the Ruby Version Manager (RVM). Being a noob myself in the Ruby world, I wanted to give some clarification on stuff that I’d wondered at the outset regarding this tool.

RVM is basically a package manager (like apt for fellow linux users); it upgrades packages, downgrades them, allows you to switch out versions, etc. The big question on my mind was “why doesn’t ruby just use apt!?” Indeed, apt had served me well for php and it seemed to be a needless complication to use some other package manager for this language.  “Why was Ruby so special that it needed its own package manager!?”  I’m still not entirely sure of the rationale behind this, but my guess is that one of the things that makes Ruby so useful is its “Gems” (Rails is one of them), for which Ruby sort of acts as a package manager in itself.  I figure this makes it much more important for users to have a more control over the versions of ruby that they’re using; either way RVM (and a few others like it) are the ways to manage ruby, so here are a few tips to make it work.

Note: These instructions might have an Ubuntu flavor to them here and there, because that’s what I use.  For the most part, they’re universal though.

To install RVM:
\curl -sSL https://get.rvm.io | bash -s stable --ruby

To check the version of ruby:
ruby -v

How can I upgrade to the latest version of ruby!?
There is no way to just upgrade ruby to the latest (whatever it happens to be). RVM seems to be all about giving control to YOU; it’s not going to make the choice for you. Here’s how I go about it.
First, I update my list of known stable ruby versions
rvm get master
Then, I check that updated list with:
rvm list known
My output looked like this:

# MRI Rubies
[ruby-]1.8.6[-p420]
[ruby-]1.8.7[-head] # security released on head
[ruby-]1.9.1[-p431]
[ruby-]1.9.2[-p330]
[ruby-]1.9.3[-p551]
[ruby-]2.0.0[-p598]
[ruby-]2.1.4
[ruby-]2.1[.5]
[ruby-]2.2.0
[ruby-]2.2-head
ruby-head
# for forks use: rvm install ruby-head- --url https://github.com/github/ruby.git --branch 2.1

The real output was actually a lot longer as it gives you ALL the packages you can get with RVM but I cut it off (we’re not interested in JRuby or anything like that).  Anyway, I checked out the list and saw that 2.2.0 was the latest so I entered:
rvm install 2.2.0

Managing installed versions:
RVM also allows a user to have many “Rubies” installed (versions of ruby).  To see which ones are installed:
rvm list
Mine looks like this:

rvm rubies

ruby-1.9.2-p320 [ x86_64 ]
* ruby-1.9.3-p392 [ x86_64 ]
=> ruby-2.2.0 [ x86_64 ]

# => – current
# =* – current && default
# * – default

I’m using 2.2.0. If I wanted to use the version of 1.9.3 I have, I would type
rvm use ruby-1.9.3-p392
Also my default was 1.9.3. If I wanted to change the default to 2.2.0, I would enter
rvm --default use 2.2.0

Upgrading RVM:
Every month or so it’s good to upgrade your rvm. To do so:
rvm get stable