I'm looking for good resources to learn more about how to write/debug/maintain init.d scripts on Ubuntu.
Do you have any links or books to recommend ?
These days init is actually being replaced by upstart in Ubuntu server. So what you probably want to do if you are writing these scripts is to try to write upstart ones instead of init. Here is a Getting Started Guide for upstart in Ubuntu.
This seemed pretty good. You also want to learn as much about bash as you can.
Remember that everything in the specific runlevel directory,
The first letter of the link,
Debugging is accomplished through liberal use of the