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: 
According to your init script, "/bin/init.d/unicorn restart" sends HUP signal to unicorn master process

------cropped

```
restart|reload)
    sig HUP && echo reloaded OK && exit 0
    echo >&2 "Couldn't reload, starting '$CMD' instead"
    su - $USER -c "$CMD"

```

-----cropped

This is what HUP does to unicorn process :

reloads config file and gracefully restart all workers. If the “preload\_app” directive is false (the default), then workers will also pick up any application code changes when restarted. If “preload\_app” is true, then application code changes will have no effect.

What you are looking for is USR2 signal which your upgrade parameter to unicorn is already doing !

USR2 signal re-executes the running binary. A separate QUIT should be sent to the original process once the child is verified to be up and running.
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 =)