How can I read a crash file on Ubuntu 12.04?

Question

php5-fpm crashed on us and we'd like to get information as to what was getting executed at the time. We can't get that from xdebug as it's been happening on production.

I mounted the drive of the failed instance onto another one (/mnt) and tried to read the crash file:

Version info

root@dev:/mnt/var/crash# cat /mnt/etc/lsb-release 
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=12.04
DISTRIB_CODENAME=precise
DISTRIB_DESCRIPTION="Ubuntu 12.04.4 LTS"

Trying to open crash file with gdb .. but this is not recognized:

root@dev:/mnt/var/crash# gdb /mnt/usr/sbin/php5-fpm _usr_sbin_php5-fpm.1002.crash 
GNU gdb (Ubuntu/Linaro 7.4-2012.04-0ubuntu2.1) 7.4-2012.04
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
For bug reporting instructions, please see:
<http://bugs.launchpad.net/gdb-linaro/>...
Reading symbols from /mnt/usr/sbin/php5-fpm...(no debugging symbols found)...done.
"/mnt/var/crash/_usr_sbin_php5-fpm.1002.crash" is not a core dump: File format not recognized

Then trying with crash:

root@dev:/mnt/var/crash# crash _usr_sbin_php5-fpm.1002.crash 

crash 6.1.6
Copyright (C) 2002-2013  Red Hat, Inc.
Copyright (C) 2004, 2005, 2006, 2010  IBM Corporation
Copyright (C) 1999-2006  Hewlett-Packard Co
Copyright (C) 2005, 2006, 2011, 2012  Fujitsu Limited
Copyright (C) 2006, 2007  VA Linux Systems Japan K.K.
Copyright (C) 2005, 2011  NEC Corporation
Copyright (C) 1999, 2002, 2007  Silicon Graphics, Inc.
Copyright (C) 1999, 2000, 2001, 2002  Mission Critical Linux, Inc.
This program is free software, covered by the GNU General Public License,
and you are welcome to change it and/or distribute copies of it under
certain conditions.  Enter "help copying" to see the conditions.
This program has absolutely no warranty.  Enter "help warranty" for details.

crash: _usr_sbin_php5-fpm.1002.crash: not a supported file format

The file itself has some basic info but the guts of it seem to be base64 encoded:

[...]
Signal: 11
Uname: Linux 3.2.0-59-virtual x86_64
UserGroups:
CoreDump: base64
 H4sICAAAAAAC/0NvcmVEdW1wAA==
[...]

Any idea on how I can read this?

Answer 1

You want to read the "How do I use these crash reports?" section here.

Use apport-unpack to unpack the core dump, which GDB will be able to analyze.