sqlite3-ruby Not Needed for Rails?

I've always thought the sqlite3-ruby gem is needed for Rails apps to
use SQLite3 databases, until the other day.

I set up a VM running Ubuntu 9.0.4, 32-bit server edition with Rails
2.2.2 to host an app I had written (by the way, the VM was
surprisingly easier to setup than the Mac it replaced).

I had neglected to install the sqlite3-ruby gem on the VM, which I had
installed on the Mac, but my app runs just fine on the VM anyway.
What gives?

If someone can enlighten me, I'd appreciate it.

Thanks!

Your first thought was correct. If you're using sqlite3 to support
your app's DB you can't even do "rake db:migrate" without having
sqlite3-ruby installed. My guess is that the either gem was already
in place or you had a "config.gem 'sqlite3-ruby'..." line in your
app's environment.rb and ran "rake gems:install" as part of the app
port to the server.

Your first thought was correct. If you're using sqlite3 to support
your app's DB you can't even do "rake db:migrate" without having
sqlite3-ruby installed. My guess is that the either gem was already
in place or you had a "config.gem 'sqlite3-ruby'..." line in your
app's environment.rb and ran "rake gems:install" as part of the app
port to the server.

You need sqlite3-ruby, but it doesn't have to be installed as a gem.
Linux distros often make ruby libraries available via their own
packaging system, if sqlite3-ruby was installed in that way then you
wouldn't need the gem on top of that.

Fred