my init.d script is blocking

[mercxi]

how do I run my init.d script in the background
Currently I have this:
/etc/init.d/sandbox
su -c /files/sandbox

[schragge]

Ubuntu uses upstart (http://manpages.ubuntu.com/manpages/precise/en/man7/upstart.7.html) instead of SysV init. It will still execute legacy init scripts on startup, but honestly I don't know how it is implemented in detail. See community/UpstartHowto.

In Debian, you manage your /etc/init.d scripts with update-rc.d (http://manpages.ubuntu.com/manpages/precise/en/man8/update-rc.d.8.html). This command generates appropriate links under /etc/rc[0-6S].d/. There's also sysv-rc-conf (http://manpages.ubuntu.com/manpages/precise/en/man8/sysv-rc-conf.8.html) in repositories. It has curses interface and is modeled after RedHat's chkconfig.

Init scripts are supposed to be automatically executed on boot, why would you want to run them in background? Certainly, they can start services or daemons that are then themselves running in background. For this, the start-stop-daemon (http://manpages.ubuntu.com/manpages/precise/en/man8/start-stop-daemon.8.html) command is usually invoked inside an init script.