In Part 1 of this series, we discussed the basics of host
security through traditional security mechanisms (DAC) and newer
efficient mechanisms (MAC). We also understood that the right
combination of both the Access Control Methods eventually leads
to an effective security policy that can be applied to any host.
We learnt that applying security to an operating system as a
whole was far more practical and efficient than applying
security to each individual application running on the operating
system, and that SELinux was one such mechanism. SELinux
achieves MAC objectives by applying a ‘Security Context’ to
subjects and objects, and by controlling access of subjects to
objects based on access control rules. In Part I, we also learnt
to enable SELinux on Red Hat Enterprise Linux. The steps are
briefly summarised below: /etc/sysconfig/selinuxand make sure it
contains the lines: - Reboot and check. In this article, we will
explore Permissive and Reboot and check. Enforcing Modes. We
will also learn a few SELinux