I need to write a script which prompts information to the user in case of an error. Is this possible using
/etc/init.d scripts +
update-rc.d? Is there any other way?
Sure, it's just a standard init script that reads input. Plenty of scripts do it in special circumstances. Be really careful, though; unless the problem you're prompting about would result in the system being completely unusable and unable to get to even the most minimal of recovery environments up and running, all your init script will do is cause the system to fail to boot, making recovery much harder.