I tried to deploy new Rails app code to a production server the other
day and took down the live site in production.  I'd like to avoid this
in the future.  Something happened in the process that affected the
live site.  The error log showed that fastthread was not found.  I had
to go into the fastthread gem and run setup.rb.  Then it told me that
Rails was not installed so I had to do a gem install Rails.  Then
there were other gems that were needed by the application and not
found so I had to reinstall those too.

I have my own staging server that this all worked on, but the staging
server is able to serve multiple sites so it is not an exact replicate
of the client's production box.  The Apache setup is such that only
one site can be served from this machine - the document root in Apache
is /project/public.

I've got a couple of questions. 1- Any idea why gems would need to be
reinstalled?  2- Can I deploy Capistrano without restarting Passenger
to put the code onto the production server and then once it's all
there, change the document root in Apache then do a deploy with the
Passenger restart?