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SELinux
The diagram below shows the process a process requesting access to a file goes through before it is granted access using SELinux:
Reference:
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/5/html/Deployment_Guide/images/SELinux_Decision_Process.png
SELinux Modes:
1) Enforcing - AVC is checked, logged and enforced
2) Permissive - AVC is checked and logged however rules are NOT enforced
3) Disabled
Managing SELinux
1) SELinux Tools
2) /etc/sysconfig/selinux
Resolving Label Issue
If SELinux has been disabled for a while, chances are the labels for some directories and files will be incorrect. To reset the system to the correct labels you will need to create the following file and then reboot the system:
/.autolabelWhen the system reboots then this file will cause the relabel to happen early in the boot process.
SE Policies
SELINUXTYPE
E.g.
You are able to target the following daemons: dhcpd, httpd (apache.te), named, nscd, ntpd, portmap, snmpd, squid
SELINUXTYPE=httpd|strict