Run yum install setroubleshoot-server-3.0.47-11.el6.x86_64 which will bring in
a bunch of packages. /usr/sbin/setroubleshootd starts a daemon so when you
tail -f /var/log/messages you'll see translated selinux errors, such as:
Jul 8 21:03:45 localhost setroubleshoot: SELinux is preventing
/usr/sbin/nginx from getattr access on the file /srv/wordpress/index.php. For
complete SELinux messages. run sealert -l 1aa6ca64-b20c-4081-bf70-039aedf7cce6
When you run the recommended command, it gives a very thorough breakdown of what went wrong and why, along with recommended fixes.
In this instance, fixingallow nginx access to that directory involved doing the
following: semanage fcontext -a -t httpd_sys_content_t "/srv/(/.*)?" followed
by restorecon -R -v /srv
More information here: https://www.nginx.com/blog/nginx-se-linux-changes-upgrading-rhel-6-6/