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Tux Machines (TM)-specific
Selinux can be confusing, but it's ordinary and default configuration is actually pretty simple. We'll examine it on Fedora Core 5.
By default, FC5 installs Selinux in "targeted" mode. You can see this in /etc/selinux/config:
# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
# enforcing - SELinux security policy is enforced.
# permissive - SELinux prints warnings instead of enforcing.
# disabled - SELinux is fully disabled.
# SELINUXTYPE= type of policy in use. Possible values are:
# targeted - Only targeted network daemons are protected.
# strict - Full SELinux protection.
# SETLOCALDEFS= Check local definition changes
As the comments imply, only certain network daemons are affected by Selinux in this configuration.
In related links:
SELinux is a mandatory access control (MAC) system available in Linux kernels as of version 2.6. Of the Linux Security Modules available, it is the most comprehensive and well tested, and is founded on 20 years of MAC research. SELinux combines a type-enforcement server with either multi-level security or an optional multi-category policy, and a notion of role-based access control. See the Resources section later in this article for links to more information about these topics.
Most people who have used SELinux have done so by using an SELinux-ready distribution such as Fedora, Red Hat Enterprise Linux (RHEL), Debian, or hardened Gentoo. These enable SELinux in the kernel, offer a customizable security policy, and patch a great number of user-land libraries and utilities to make them SELinux aware.
If you're like many users who simply want the system to work as before, but a bit more securely, you can query and manipulate SELinux by using familiar applications and by writing security policies using a higher level language.