Question: Following is link to my init script for unicorn.
<https://gist.github.com/1466775>

Restart command has never worked for me. I am using upgrade to restart unicorn after each deploy. But whenever there is major changes like new gems being added, upgrade won't work. Recently, i replaced hoptoad gem with airbrake and it errors out saying 'uninitialized constant Airbrake (NameError)'. But when i stopped and started unicorn again, it worked fine. Does the problem lies in init script or its different problem?

Thanks.

Answer: 
I had a very similar problem and finally [found the solution](http://blog.willj.net/2011/08/02/fixing-the-gemfile-not-found-bundlergemfilenotfound-error/)

I had looked through the logs before but obviously failed to see the `(Bundler::GemfileNotFound)` error. Turns out there are old references to earlier releases and once the gem file changes, the new master silently fails. Tail -f your unicorn log to see what happens. My issues were all fixed as per the link with the following in my unicorn.rb

```
 before_exec do |server|
    ENV['BUNDLE_GEMFILE'] = "#{root}/Gemfile"
 end 

```
I had the same issue, but I was using rbenv which was installed on per user basis.
I used this [init script](https://github.com/railscasts/335-deploying-to-a-vps/blob/master/blog-nginx/config/unicorn_init.sh)

I figured out that since my rbenv installed on per user basis I need to slightly change this:

```
CMD="cd $APP_ROOT; bundle exec unicorn -D -c $APP_ROOT/config/unicorn.rb -E production"

```

with this:

```
CMD="cd $APP_ROOT; ~/.rbenv/bin/rbenv exec bundle exec unicorn -D -c $APP_ROOT/config/unicorn.rb -E production"

```

Hope it will help you!

P.S. or somebody else since it's an old question =)