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Chapter 6. Configuring basic system security

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Computer security is the protection of computer systems and their hardware, software, information, and services from theft, damage, disruption, and misdirection. Ensuring computer security is an essential task, in particular in enterprises that process sensitive data and handle business transactions.

This section covers only the basic security features that you can configure after installation of the operating system.

6.1. Enabling the firewalld service

A firewall is a network security system that monitors and controls incoming and outgoing network traffic according to configured security rules. A firewall typically establishes a barrier between a trusted secure internal network and another outside network.

The firewalld service, which provides a firewall in Red Hat Enterprise Linux, is automatically enabled during installation.

To enable the firewalld service, follow this procedure.


  • Display the current status of firewalld:

    $ systemctl status firewalld
    ● firewalld.service - firewalld - dynamic firewall daemon
       Loaded: loaded (/usr/lib/systemd/system/firewalld.service; disabled; vendor preset: enabled)
       Active: inactive (dead)
  • If firewalld is not enabled and running, switch to the root user, and start the firewalld service and enable to start it automatically after the system restarts:

    # systemctl enable --now firewalld

Verification steps

  • Check that firewalld is running and enabled:

    $ systemctl status firewalld
    ● firewalld.service - firewalld - dynamic firewall daemon
       Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; vendor preset: enabled)
       Active: active (running)

Additional resources

6.2. Managing basic SELinux settings

Security-Enhanced Linux (SELinux) is an additional layer of system security that determines which processes can access which files, directories, and ports. These permissions are defined in SELinux policies. A policy is a set of rules that guide the SELinux security engine.

SELinux has two possible states:

  • Disabled
  • Enabled

When SELinux is enabled, it runs in one of the following modes:

  • Enabled

    • Enforcing
    • Permissive

In enforcing mode, SELinux enforces the loaded policies. SELinux denies access based on SELinux policy rules and enables only the interactions that are explicitly allowed. Enforcing mode is the safest SELinux mode and is the default mode after installation.

In permissive mode, SELinux does not enforce the loaded policies. SELinux does not deny access, but reports actions that break the rules to the /var/log/audit/audit.log log. Permissive mode is the default mode during installation. Permissive mode is also useful in some specific cases, for example when troubleshooting problems.

Additional resources

6.3. Ensuring the required state of SELinux

By default, SELinux operates in enforcing mode. However, in specific scenarios, you can set SELinux to permissive mode or even disable it.


Red Hat recommends to keep your system in enforcing mode. For debugging purposes, you can set SELinux to permissive mode.

Follow this procedure to change the state and mode of SELinux on your system.


  1. Display the current SELinux mode:

    $ getenforce
  2. To temporarily set SELinux:

    1. To Enforcing mode:

      # setenforce Enforcing
    2. To Permissive mode:

      # setenforce Permissive

      After reboot, SELinux mode is set to the value specified in the /etc/selinux/config configuration file.

  3. To set SELinux mode to persist across reboots, modify the SELINUX variable in the /etc/selinux/config configuration file.

    For example, to switch SELinux to enforcing mode:

    # 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 - No SELinux policy is loaded.

    Disabling SELinux reduces your system security. Avoid disabling SELinux using the SELINUX=disabled option in the /etc/selinux/config file because this can result in memory leaks and race conditions causing kernel panics. Instead, disable SELinux by adding the selinux=0 parameter to the kernel command line. For more information, see Changing SELinux modes at boot time.

Additional resources

6.4. Additional resources

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