Reposted from Superuser - Installing Ruby on Rails on Ubuntu 10.04: A Living Nightmare

I'm reposting this here from my original post on Superuser[1], to
hopefully get more relevant feedback from more experienced RoR users.
I need to get a RoR environment up and running, because I have a
client that needs some RoR work done on her website. Although I'm new
to RoR, I'm a quick learner and was expecting installing and setting
up the environment was easy, so I could focus my effort on site
development. I've already spent five days trying to get the
environment up so I could just begin working. I'll probably have
follow up questions to this group (seems I can't get script/server to
work at all) - but for now, this is the immediate concern.

Update #3: Starting over from scratch, shortened this post, decided to
re-install a clean copy of Ubuntu 10.04 on a VM and go through the
walk-through[0] again. So, all the steps go without a hitch. As root:

root@ubuntu:~/rubygems-1.3.7# ruby -v
ruby 1.8.7 (2010-01-10 patchlevel 249) [x86_64-linux]
root@ubuntu:~/rubygems-1.3.7# gem -v
1.3.7
root@ubuntu:~/rubygems-1.3.7# rails -v
Rails 2.3.8
Now, as myself (in a separate term):

emptyset@ubuntu:~$ ruby -v
ruby 1.8.7 (2010-01-10 patchlevel 249) [x86_64-linux]
emptyset@ubuntu:~$ gem -v
/usr/local/lib/site_ruby/1.8/rubygems.rb:10:in `require': no such file
to load -- rubygems/defaults (LoadError)
    from /usr/local/lib/site_ruby/1.8/rubygems.rb:10
    from /usr/local/bin/gem:8:in `require'
    from /usr/local/bin/gem:8
emptyset@ubuntu:~$ rails -v
bash: /usr/bin/rails: Permission denied

So, this appears to be a permissions issue, but I don't understand
why. Specifically, if I have to start making things go+rx all over the
place, I really need to understand which specific files need the
permissions change.

Site references:
[0] http://castilho.biz/blog/2010/05/08/how-to-install-ruby-on-rails-on-ubuntu-10-04-lucid-lynx/
[1] http://superuser.com/questions/156498/installing-ruby-on-rails-on-ubuntu-10-04-a-living-nightmare

I installed Ruby and Rails on Ubuntu 10.04 by following this guide:
https://help.ubuntu.com/community/RubyOnRails.
Everything went well.

Quick steps:
1. > sudo apt-get install ruby-full build-essential
2. Download and install latest rubygems. Do not use apt-get because
rubygems update itself and corrupts apt-get.
3. > sudo gem install rails
4. test your environment! > rails ~/my_test_app

I would strongly suggest you look into rvm to manage your ruby/rails
environments. But you might also want to install gem as your own user
as opposed to root. The new gems will be kept somewhere in your home
directory.

- Victor

Victor Stan wrote:

I would strongly suggest you look into rvm to manage your ruby/rails
environments. But you might also want to install gem as your own user
as opposed to root. The new gems will be kept somewhere in your home
directory.

That always seems to cause problems. I'd rather keep gems available
system-wide.

Thanks! I updated my answer on SU and linked to this post. My best
guess is that:

  apt-get install ruby rdoc libopenssl-ruby build-essential

Doesn't quite cover everything that's needed to run gem
effectively...ruby-full on a clean VM install worked great. Much
appreciated.

A guide which I found useful after failing to install properly (I have not created the gem symlink) is http://ubuntuforums.org/showthread.php?t=1459056. Covers pretty much everything I ended up doing through trial and error. Took about 30 mins from start to finish.

Note: - where it gives the link to get rubygems don’t forget to check for the latest version and modify the command to match.