Ubuntu – /usr/bin/ruby1.9.1: No such file or directory — /usr/share/rubygems-integration/1.9.1/gems/bundler-1.3.5/bin/bundle (LoadError)

The PATH is what the env program uses to search for your executables. You can change this per-user (in the $HOME/.bashrc). In order to do that, run nano $HOME/.bashrc and go to the last line, add a new line

export PATH=$PATH:/usr/local/rvm/rubies/ruby-2.1.1/bin

To change it at a system level you sudo nano /etc/login.defs and change this line

ENV_PATH        PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games

to

ENV_PATH        PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/usr/local/rvm/rubies/ruby-2.1.1/bin

The default PATH crontab is using is "only" /usr/bin:/bin, however you can adjust it.

Instead of writing the things in that script try adding it directly into the crontab command:

@reboot PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/rvm/gems/ruby-1.9.2-p180/bin"; /etc/init.d/unicorn_myapp start > /home/username/unicorn_start.out 2>&1

You can also add the path variable above every cronjob so it's applicable to every task you put in there:

 PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/rvm/gems/ruby-1.9.2-p180/bin"
 #
 #
 * * * * * myjob.sh
 @reboot /home/username/unicorn_start.sh > /home/username/unicorn_start.out 2>&1