How to Replace the Hardened Kernel of cPanel with a Standard Kernel?

In web hosting, cPanel is a common, graphical, third-party control panel that helps in the administration of website hosting accounts through a simpler process and the use of automation. CPanel also employs several key strategies. For instance, they employ the KernelCare kernel, which effectively enhances security by patching the kernel live. However, there may be some cases where it may be necessary to replace the hardened kernel with a regular one due to compatibility issues, for what have you, or performance dependency.

This blog post will explain how to remove the Rock and replace it. Let’s get started!

Understanding Kernels and Their Roles

Hardened Kernel

A hardened kernel is modified to enhance security, reducing vulnerabilities that can be exploited by attackers. KernelCare, used by cPanel, ensures that security patches are applied without needing to reboot the server, minimizing downtime.

Standard Kernel

A standard kernel, often provided by distributions like CentOS or Ubuntu, doesn't include the extra security modifications and live patching features of a hardened kernel. It follows the updates and patches provided by the operating system’s maintainers.

Why Replace the Hardened Kernel?

While the hardened kernel offers significant security benefits, there might be reasons to switch to a standard kernel:

Compatibility Issues: Some applications or custom modules might not be compatible with the hardened kernel.

Specific Requirements: Certain performance or functionality requirements might necessitate using the standard kernel.

Preference: Administrators might prefer using the default kernel provided by their operating system for simplicity or consistency across different servers.

Steps to Replace the Hardened Kernel

1. Preparing the Environment

Before making any changes, ensure you have proper backups and access to your server's console. This is crucial as kernel changes can render your system unbootable if not done correctly.

2. Identifying the Current Kernel

First, check the current kernel version to confirm you are using a hardened kernel:

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uname -r

This command will display the current kernel version. If it's KernelCare or another hardened version, proceed with the following steps.

3. Installing the Standard Kernel

For CentOS/RHEL systems, you can install the standard kernel using the following commands:

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yum install kernel

For Ubuntu/Debian systems, use:

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apt-get install linux-image-generic

4. Updating the Bootloader

After installing the standard kernel, you need to update the bootloader to ensure the system boots with the new kernel. On CentOS/RHEL systems, this can be done using:

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grub2-set-default 0

For Ubuntu/Debian systems:

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Update-grub

5. Removing the Hardened Kernel

To prevent the system from reverting to the hardened kernel, you should remove it. On CentOS/RHEL, use:

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yum remove kernelcare

For Ubuntu/Debian:

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apt-get remove kernelcare

6. Rebooting the Server

After making these changes, reboot the server to apply the new kernel:

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Reboot

7. Verifying the Changes

Once the server has rebooted, verify that it is using the standard kernel:

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uname -r

Ensure the output matches the version of the standard kernel you installed.

Post-Replacement Considerations

Security Patching

Without KernelCare, you'll need to manually apply security patches and updates to your kernel. Regularly check for updates and apply them using:

For CentOS/RHEL:

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yum update kernel

For Ubuntu/Debian:

bash

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apt-get update && apt-get upgrade

Monitoring and Maintenance

Keep an eye on your system’s performance and stability. Replacing the kernel can have implications on your server's behavior, so monitoring tools like Nagios, Zabbix, or even simple logging can help you catch any issues early.

Backup and Recovery

Maintain a robust backup and recovery plan. Kernel updates and changes can sometimes lead to unexpected problems, so having recent backups ensures you can quickly restore your system if needed.

Final Words

Replacing cPanel's hardened kernel with a standard kernel involves several critical steps, from installing the new kernel to updating the bootloader and removing the hardened kernel. While this process can provide compatibility and performance benefits, it also requires diligent security patching and system monitoring. That’s it! You can now successfully transition to a standard kernel while maintaining the stability and security of your cPanel server.