I know it's sacrilegious for some to disable a security feature on a platform, but SELinux (an enhanced Linux security feature) has left me no choice but doing exactly that on Linux.
SELinux was added to Linux to give it additional security measures beyond what it inherited From Unix. By default many of the Linux distros such as Fedora have SELinux built into their kernels and enabled upon install.
The issue is that SELinux can be so restricting and obsessive about curbing malicious activity that it can also hinder normal operations leading to server stress or errors. Having been bitten by SELinux multiple times, I have vowed to deactivate it every time I install Linux on a host. The one time I forgot to disable it, the Varnish server I have setup for my company nearly died taking the company's web site along for the ride. Looking inside the messages file, this arcane message is what I saw in prodigious numbers:
setroubleshoot: SELinux is preventing irqbalance from mmap_zero access on the memprotect Unknown. For complete SELinux messages. run sealert -l efce…
I know the security sticklers would accuse me of not setting up SELinux correctly and for the record SELinux is very configurable. But my most favorite setting for SELinux is disabling it in the /etc/selinux/config file by setting SELINUX=disabled.
I don't have the time nor the inclination to learn SELinux's every minutia, which may or may not protect my hosts completely anyways. The old fashion file permissions, file ownership, suexec, sudo, suid, running daemons with least privilege, and a good dose of firewalling is good enough for me. Feel free to disagree.