Enable core dumps in Apache

apache-2.2arch-linuxdump

I would like to enable core dumps in my Apache web server.
Since I have PHP 5.5 and OPcache my Mediawiki site crashes with the following error:

child pid ... exit signal Segmentation fault (11)

So I would like to get more information through the core dump.

I created a directory: /tmp/apache-coredump owned by http:http (my apache user and group) and with the 777 rights.
I added to the httpd.conf file:

CoreDumpDirectory   "/tmp/apache-coredump"

But, now (with the CoreDumpDirectory instruction) my Apache server crashes on start-up:

sudo systemctl restart httpd

Job for httpd.service failed. 
See 'systemctl status httpd.service' and 'journalctl -xn' for details.

The journal give me the following info

apachectl[4149]: CoreDumpDirectory /tmp/apache-coredump does not exist

I checked, the directory exist 0_°

Edit:
I changed the CoreDumpDirectory instruction in the httpd.conf file and it allows me to start my web server 

CoreDumpDirectory /tmp

Without the CoreDumpDirectory instruction, there is no core dump generated in the ServerRoot (/etc/httpd) directory.
I'm on Archlinux 3.10.6-2 64-bits with Apache/2.2.25 Prefork

Best Answer

Core dumps are generally disabled by default since they tend to waste disk space, you need to switch them on for your apache session.

$ ulimit -a
core file size          (blocks, -c) 0
[...]
$ ulimit -c unlimited
$ systemctl restart httpd

Also, do you have SELinux enabled? Output of ls -alZ /tmp/apache-coredump

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