Red Hat Enterprise Linux 5 Administration Unleashed

58CHAPTER 2Post-Installation ConfigurationFIGURE 2.1Welcome to the Setup AgentThe first task is to read the License Agreement, which explains that the software can becopied, modified, and redistributed with the exception of a few image files such as the RedHat logo. You must agree to the license before continuing to use Red Hat Enterprise Linux.The next step is to determine whether or not to enable the built-in firewall (see Figure2.2). If you prefer to configure a custom firewall using IPTables (refer to Chapter 24,“Configuring a Firewall”) you can either disable the built-in firewall or enable it for nowand then disable it later after configuring IPTables.To modify the firewall settings later, start the Security Level Configuration Tool by selectingthe System menu from the top panel of the desktop and selecting Administration,Security Level and Firewall or by executing the system-config-securitylevelcommand. If you are not root when you run the tool, you will be prompted to enter theroot password before continuing.Security-Enhanced Linux, or SELinux, allows administrators to add an additional layer ofsecurity to Linux. Instead of relying on users to secure their files with file permissions andsoftware distributors to make the default file permissions of critical system files secure,SELinux only allows processes access to files they absolutely need to function. For detailson SELinux, refer to Chapter 23, “Protecting Against Intruders with Security-EnhancedLinux.” Select one of three SELinux modes (see Figure 2.3):. Enforcing: Configure SELinux for the system using the default targeted policy. Permissive: Only warn about services protected by SELinux. Disabled: Turn off SELinux