Debugging sigsegv faulting Apache

Question

What's the best way to get meaningful gdb backtraces from Apache server which misbehaves on production?

 [Tue Aug 02 16:07:12 2011] [notice] child pid 27681 exit signal Segmentation fault (11)

It's probably some Apache module doing bad things, but I need symbolic gdb traceback to get started debugging what and where.

• How to enable debug symbols for Apache on Ubuntu

• How to extract one and only one core dump from Apache child

• How to reopen this file in gdb

Ubuntu 8.04 / Linux.

Answer 1

See configure an Apache web server for core dump on segmentation faults.

You might also have to set core dump size limit to unlimited in /etc/security/limits.conf:

*    hard    core    unlimited

Log in, check that core size is not limited by saying ulimit -a and restart apache.

To analyze the core file, start gdb:

gdb /usr/lib/apache2/mpm-worker/apache2 /path/to/core.dump

gdb command bt prints out the stack trace.