On Sat, Nov 27, 2010 at 08:23:34PM -0500, Nico Kadel-Garcia wrote:
The "working system" in that analogy is software, not necessarily nor even likely to be the kernel itself. But yes, it can trash a production critical web or software application that didn't follow the sensible, but often poorly understood, policies of SELinux. This is particularly common with 3rd party web applications, the sort of thing we grab from Sourceforge and try ourselves. (Lilac, the Nagios configuration tool, particularly comes to mind.)
I'd have to dig back to rediscover the Lilac issues, but I remember running out of time to sort them all out and having to leave SELinux off of that server.
heh, fail.
You run it in Permissive mode, you deal with the exceptions as they arise while the software is running in its normal environment and while its running normally using any of the documented methods. You thoroughly test the application in such a manner and once you have ironed out any and all issues by putting together a custom policy, setting the right SElinux booleans, etc, you then enable Enforcing mode. There is really no reason that SElinux should have a negative impact on your application or server if you use Permissive first.
John