nixCraft posted a guide about debugging crashed Linux application core files

Core dumps are often used to diagnose or debug errors in Linux or UNIX programs. Core dumps can serve as useful debugging aids for sys admins to find out why Application like Lighttpd, Apache, PHP-CGI or any other program crashed. Many vendors and open source project author requests a core file to troubleshoot a program. A core file is generated when an application program abnormally terminates due to bug, operating system security protection schema, or program simply try to write beyond the area of memory it has allocated, and so on. This article explains how to turn on core file support and track down bugs in programs.

  HowTo: Debug Crashed Linux Application Core Files Like A Pro