"kill -0" has no effect, use "kill -9" instead

cat app_path/current/tmp/pids/unicorn.pid
# 8727
kill -0 `cat app_path/current/tmp/pids/unicorn.pid`
ps aux | grep "unicorn"
# ... 8727 ... app_pathl/current/config/unicorn/production.rb -E deployment -D ...