How to Check and Disable SELinux on CentOS 6.3

Security-Enhanced Linux (SELinux) is a feature inherent to Linux that provides a robust security mechanism for supporting access control security policies at the kernel level. SELinux performs checks for allowed operations after the standard Linux discretionary access controls have been checked.

This tutorial will guide you through the process of checking the SELinux status and disabling SELinux on CentOS 6.3. This is a crucial step for webmasters and website administrators who are looking to optimize their server’s performance and security settings.

Checking SELinux Status on CentOS 6.3

To check the status of SELinux on your CentOS 6.3 system, you can use the following commands:

[root@centos63 ~]# sestatus
SELinux status:                 enabled
SELinuxfs mount:                /selinux
Current mode:                   enforcing
Mode from config file:          enforcing
Policy version:                 24
Policy from config file:        targeted

or

[root@centos63 ~]# getenforce
Enforcing

These commands will provide you with the current status of SELinux on your system, whether it is enabled or disabled, and the current mode of operation.

Disabling SELinux on CentOS 6.3 Permanently

To disable SELinux on CentOS 6.3 permanently, you need to modify the SELinux configuration file. You can view the current configuration using the cat command:

[root@centos63 ~]# cat /etc/selinux/config

# 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.
SELINUX=enforcing
# SELINUXTYPE= can take one of these two values:
#     targeted - Targeted processes are protected,
#     mls - Multi Level Security protection.
SELINUXTYPE=targeted

or

[root@centos63 ~]# cat /etc/sysconfig/selinux

# 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.
SELINUX=enforcing
# SELINUXTYPE= can take one of these two values:
#     targeted - Targeted processes are protected,
#     mls - Multi Level Security protection.
SELINUXTYPE=targeted

To disable SELinux, you need to change the SELINUX=enforcing line to SELINUX=disabled:

# 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.
SELINUX=disabled
# SELINUXTYPE= can take one of these two values:
#     targeted - Targeted processes are protected,
#     mls - Multi Level Security protection.
SELINUXTYPE=targeted

Please note that this change will take effect after your next system reboot. You can check the status of SELinux after the reboot using the sestatus command:

[root@centos63 ~]# sestatus
SELinux status: disabled

Disabling SELinux on CentOS 6.3 Immediately Without Reboot

If you want to disable SELinux on CentOS 6.3 immediately without having to reboot your system, you can use the setenforce command:

[root@centos63 ~]# setenforce 0

After running this command, you can check the status of SELinux using the getenforce command:

[root@centos63 ~]# getenforce
Permissive

This command will set SELinux to permissive mode, effectively disabling it until the next system reboot.

Commands Mentioned

• sestatus – Checks the status of SELinux
• getenforce – Checks the enforcing mode of SELinux
• cat /etc/selinux/config – Displays the current SELinux configuration
• setenforce 0 – Sets SELinux to permissive mode, effectively disabling it until the next reboot

Conclusion

Understanding and managing SELinux is a vital aspect of maintaining a secure and efficient Linux server. This tutorial has provided you with the necessary steps to check the status of SELinux and disable it, either permanently or temporarily, on CentOS 6.3.

Remember, while disabling SELinux might be necessary for certain applications to function correctly, it’s generally recommended to keep it enabled whenever possible to benefit from the additional layer of security it provides.

By following these guides and understanding the underlying principles, you can ensure that your server is optimized for performance, security, and reliability.

FAQs

1. What is SELinux?

   SELinux, or Security-Enhanced Linux, is a security feature of Linux that provides a mechanism for supporting access control security policies in the Linux kernel.

2. How do I check the status of SELinux?

   You can check the status of SELinux using the ‘sestatus’ or ‘getenforce’ commands in the terminal.

3. How do I disable SELinux permanently?

   To disable SELinux permanently, you need to modify the SELinux configuration file (/etc/selinux/config) and change ‘SELINUX=enforcing’ to ‘SELINUX=disabled’. This change will take effect after the next system reboot.

4. How do I disable SELinux without rebooting?

   You can disable SELinux without rebooting by using the ‘setenforce 0’ command. This will set SELinux to permissive mode, effectively disabling it until the next system reboot.

5. What is the difference between enforcing, permissive, and disabled modes in SELinux?

   In enforcing mode, SELinux enforces the security policy on the system. In permissive mode, SELinux does not enforce the security policy but instead logs policy violations. In disabled mode, no SELinux policy is loaded on the system.