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If you want to be able to install gems locally on a Dreamhost shared hosting plan, you should be able to do it. You’ll need to set some environment variables; here’s what I’ve done.

If you try to install a gem in your dreamhost shared hosting account, you’ll get a permission denied error. That’s because rubygems is trying to put the gem in /usr/local/lib/ruby/gems/1.8/ and, I’m sorry, but you can’t write to there. Now, you can do this:

[your-DH-server]$ mkdir ~/mygems
[your-DH-server]$ gem install some_gem --install-dir ~/mygems

This will let you install a gem, but there’s still a problem: rubygems is not going to be able to find the gems you install in that directory. You could change the GEM_HOME environment variable to point to ~/mygems (or whatever you want to call your gem directory), but that would be a bad idea: rubygems would no longer be able to find the gems that are already on the Dreamhost server (and there are quite a few). Also, GEM_HOME (as I understand it) should only point to one gem repository. However, there is another environment variable, GEM_PATH, which can have multiple directories in it. So, we’ll do this:

Basically, what you just did is tell bash to set a couple environment variables as soon as you start a new shell, ie, any time you log in with ssh, for example. By setting GEM_HOME first, and adding it to GEM_PATH, you make sure that all Dreamhosts gems will still be findable. So will yours.

Now, other than to confirm that this all seems to work, I haven’t tested this extensively, yet. Use at your own risk.

I believe you can also put libraries which would normally be installed as gems into your vendor/ directory in your Rails project — Mephisto does this, for example. Presumably, this is to make Mephisto easier to install — they don’t need to have a long “howto” about installing various plugins or gems before Mephisto will work.

I started out wanting to talk about Rails on shared hosting in general, but I’ll save that for another post. If this post was helpful or interesting, please consider leaving some feedback in the comments. Also, if I have anything wrong, or if what I’ve suggested could cause some other problem that I haven’t considered, please let me know!