Famous SELinux Contexts

1. httpd SELinux context

                                        chcon -v --type=httpd_sys_content_t /path/to/dir

2.httpd SELinux context

                   chcon -Rv --type=httpd_sys_content_t /path/to/dir

3. Restore old/default context

                   restorecon -Rv -n /var/www/html

                    ;  -n switch to prevent any relabelling occurring.
4. Changing default port for services permitted SELinux

                                     #  semanage port -l
                    # semanage port -a -t http_port_t -p tcp 81
5. For Nagios

chcon -R -t httpd_sys_content_t /usr/local/nagios


  1st command to see what are the supported services. 2nd one changing default port for http service.

Note: Give me time to write them with proper explanation. 

More: http://wiki.centos.org/TipsAndTricks/SelinuxBooleans