How to Downgrade Kernel in Linux Step-by-Step Methods, Pitfalls, and Best Practices

The Linux kernel is the core component of any Linux-based operating system. It is the intermediary between userland processes and the hardware, managing memory, CPU scheduling, peripheral devices, file systems, and other critical functionalities. When you power your Linux system and launch applications, the kernel ensures everything runs smoothly. Over the years, Linux has become renowned for its versatility, stability, and security, mainly due to its kernel’s robust design and open-source development model.

Even though newer kernel versions often introduce performance improvements, hardware support, and security patches, occasional missteps can occur. Sometimes, an upgrade might break hardware drivers, introduce an unstable patch, or cause performance regressions. When that happens, knowing how to downgrade kernel can save time, frustration, and potential downtime, particularly for production servers or mission-critical systems.

This comprehensive guide will teach you how to revert to an older kernel safely and effectively. You will discover methods tailored to popular Linux distributions such as Ubuntu, Debian, Fedora, CentOS, and Arch Linux. You will also gain insights into best practices, common pitfalls, troubleshooting tips, and steps you can take to avoid automatic kernel upgrades. By the end of this guide, you will be well-equipped to manage your system’s kernel versions with minimal risk.

Downgrading the kernel can be daunting, mainly if you have never performed such an operation. Yet, with sufficient planning, careful consideration, and knowledge of your distribution’s package management tools, the process can be executed smoothly. Whether you are a seasoned system administrator or a curious Linux hobbyist, understanding how to perform kernel downgrades will expand your skill set and help you keep your systems running reliably.

Why Would You Downgrade Your Linux Kernel?

Downgrading the Linux kernel is usually a reactive measure rather than a routine procedure. Sticking to the latest stable kernel is often recommended for security patches, driver updates, and new features. However, there are multiple scenarios where reverting to a previous kernel may be necessary.

• Hardware or Driver Incompatibility
  Newer kernels might drop support for specific older hardware or change APIs in ways that break proprietary drivers (e.g., NVIDIA graphics, certain Wi-Fi chipsets, or specialized hardware controllers). When these incompatibilities occur, reverting to a known stable kernel can restore functionality immediately while waiting for driver updates or patches.
  
• Performance Degradation
  Performance regressions can manifest in many ways: your system may feel sluggish, CPU usage may spike, or specific tasks may take significantly longer. If the root cause is a kernel regression (for instance, a new scheduler tweak), rolling back to a kernel version with proven stable performance can be a worthwhile solution.
  
• Stability Concerns
  Kernel panics, random crashes, or frequent freezes are classic signs of kernel instability. Although the Linux development community thoroughly tests new releases, bugs can still slip through. If a new kernel introduces random system instability, downgrading to a known reliable version is a practical first step, especially for production servers where every second of downtime can be costly.
  
• Application Compatibility
  Specific enterprise software, virtualization tools, or custom kernels may only support specific kernel versions. If your critical software fails after a kernel upgrade, rolling back to a compatible version can restore operation until a patch or update is released.
  
• Regression Testing
  Some system administrators or developers conduct regression tests across various kernel versions to pinpoint where a bug or performance issue was introduced. Installing and running older kernels is essential for effective testing.
  
• Security Anomalies
  Although newer kernels usually address security vulnerabilities, there could be rare cases where a new release inadvertently introduces other security flaws or breaks existing security mechanisms. In such situations, reverting to a prior version might be temporary until an official fix is released.

Downgrading should not be your long-term solution. Typically, the best practice is to monitor the kernel release notes, test new versions in a non-production environment if possible, and only use an older kernel until the issues in the newer one are resolved. Still, knowing how to downgrade is invaluable for any Linux user or administrator.

Key Considerations Before Downgrading

Before you begin the downgrade process, it is essential to assess the potential risks and prepare your system adequately. Downgrading the kernel has its pitfalls, and a misstep can lead to system instability or an unbootable computer.

Data Backup

Always back up important data, configuration files, and unique software settings. Though a kernel downgrade should not directly affect user data, any core system-level operation carries a degree of risk. If something goes wrong, having a reliable backup can be the difference between a quick rollback and a long recovery process.

Security Patches

Older kernels may lack security patches in newer releases, potentially leaving your system vulnerable. If you downgrade, understand that you may expose yourself to threats that newer kernels have mitigated. Keep track of security bulletins for the kernel version you decide to install.

Dependency Conflicts

Some Linux distributions and third-party software may rely on features or APIs available only in the latest kernel versions. Downgrading can cause package conflicts, broken drivers, or missing functionality. Investigate dependencies before proceeding, especially if your system runs services that cannot tolerate downtime.

Selecting the Correct Version

Carefully select the kernel version to which you plan to revert. If you have been running a 5.8.x kernel and you know that 5.7.x was stable, it makes sense to revert to 5.7.x. However, if 5.4.x is the Long Term Support (LTS) kernel that worked flawlessly in the past, consider reverting to that version instead. Ensure the version you choose is compatible with critical drivers and applications.

Bootloader Configuration

If you install more than one kernel package, your bootloader (often GRUB) will list multiple kernel entries. Make sure you know how to configure GRUB to set the default kernel. This includes editing /etc/default/grub or using GRUB utilities to set the desired entry as your system’s first boot option.

Rollback Plan

Before you downgrade, have a strategy for what to do if the older kernel introduces new issues or fails to resolve the original problem. Often, the best approach is to keep several kernels installed at once. You can try different versions or revert to your latest working configuration anytime without reinstalling from scratch.

By considering these factors, you will be better prepared to handle any complications that arise and ensure the smoothest possible downgrade experience.

How to Identify Your Current Kernel Version

Before downgrading, you should confirm which kernel version you are currently running. This helps you decide which older version you want to revert to and ensures you have the correct starting point for troubleshooting.

Use the following command in the terminal:

uname -r

This will display the exact kernel version, such as 5.15.0-60-generic, 6.0.12-arch1-1, or 4.18.0-240.el8.x86_64. If you want more detailed system information, including your distribution name and architecture, you can use the following:

uname -a

Once you have identified your current kernel, you can investigate which older versions are available in your distribution’s repositories or which ones you have previously installed. That knowledge will guide the downgrade process effectively.

Downgrading on Ubuntu and Debian-Based Distributions

Ubuntu, Debian, Linux Mint, and other Debian-based distributions utilize the .deb package format and the APT package manager (alongside tools like dpkg). Reverting to an older kernel is typically straightforward if the version you want is still available in the repositories or remains installed on your system.

Checking Installed Kernels

First, list all installed kernel images:

dpkg --list | grep linux-image

You will see packages named something like linux-image-5.15.0-60-generic or linux-image-5.4.0-104-generic. If the older kernel you want is already on your system, you can configure your bootloader to use it without installing anything new.

Installing an Older Kernel

If your preferred older kernel is not installed, you can attempt to install it from the repositories:

sudo apt-get update
sudo apt-get install linux-image-5.4.0-104-generic

Replace 5.4.0-104-generic with the exact version you desire. If that package is no longer available in the default repositories, you might have to search in “old releases” or “archive” repositories. Alternatively, you can manually download the .deb files from Ubuntu’s or Debian’s official archives and install them with dpkg -i. Ensure you also install the matching headers package (e.g., linux-headers-5.4.0-104-generic) if needed for proprietary drivers.

Updating GRUB

After installing the older kernel, update GRUB:

sudo update-grub

On reboot, access the GRUB menu often by pressing Shift or Esc during startup and select “Advanced options for Ubuntu” (or Debian) to choose the newly installed kernel. If you want this older kernel to be your default, you can configure it by editing /etc/default/grub and using commands like sudo grub-set-default.

Keeping or Removing the Newer Kernel

You can keep multiple kernel versions installed, often recommended for testing and fallback purposes. If you want to remove the newer kernel to avoid confusion, use:

sudo apt-get remove linux-image-<newer-kernel-version>

However, always ensure at least one known good kernel remains installed so you can still boot if your preferred kernel fails.

Downgrading on Fedora and CentOS

Fedora, CentOS, and Red Hat Enterprise Linux (RHEL) rely on the RPM package format and use package managers such as dnf or yum. Though the commands differ, the kernel downgrading procedure is comparable to Debian-based distributions.

Checking Current and Available Kernels

On Fedora, check which kernels are installed with:

dnf list installed kernel

On CentOS:

yum list installed kernel

This will show the kernel packages currently on your system. Depending on your distribution, you can use the dnf list available kernel or yum list available kernel to see what is available in the repositories.

Installing an Older Kernel

If the older kernel you want is listed, install it as follows:

Fedora:

sudo dnf install kernel-5.15.6-200.fc35

CentOS:

sudo yum install kernel-3.10.0-1160.el7

Replace the version number with the kernel you need. If the kernel package is no longer in the standard repositories, search for it in archive repositories or manually download the RPM from a trusted source. You may also need to install kernel headers and kernel-devel packages that match your kernel version, mainly if you use proprietary drivers or compile modules.

Updating GRUB

Fedora and CentOS use GRUB (or a variant) for boot management. After installing the older kernel, GRUB should automatically detect it. However, you can manually rebuild the GRUB configuration if necessary:

sudo grub2-mkconfig -o /boot/grub2/grub.cfg

The location for UEFI systems may differ, often /boot/efi/EFI/fedora/grub.cfg or /boot/efi/EFI/centos/grub. cf.

Selecting or Setting the Default Kernel

Reboot and access the GRUB menu. You should see multiple kernel entries. Choose the older kernel to verify functionality. If you want to set it as the default, identify the menu entry index:

sudo awk -F\' '$1=="menuentry " {print i++ " : " $2}' /boot/grub2/grub.cfg

Then, set the default kernel by its index:

sudo grub2-set-default <index-number>

Verify with:

sudo grub2-editenv list

Reboot to confirm the older kernel is the default. You may remove the newer kernel if desired, but keeping at least one additional kernel for fallback is generally safer.

Downgrading on Arch Linux

Arch Linux is a rolling-release distribution that constantly delivers the newest packages, including the kernel. This model makes Arch extremely up-to-date but can complicate downgrades since older packages are quickly removed from the primary repositories.

Using the Arch Linux Archive (ALA)

The Arch Linux Archive provides snapshots of the official repositories from specific dates in the past. To downgrade your kernel:

1. Choose a date before the problematic kernel update occurred.

Edit /etc/pacman.conf to temporarily point to that snapshot:
[core]
Server = https://archive.archlinux.org/repos/2022/01/01/core/os/$arch
[extra]
Server = https://archive.archlinux.org/repos/2022/01/01/extra/os/$arch
[community]
Server = https://archive.archlinux.org/repos/2022/01/01/community/os/$arch

2. Run

sudo pacman -Syy 

to refresh the package databases, install the older linux package with 

sudo pacman -S linux

3. Remember to install Linux headers if you need to compile modules.

Once you have verified that the old kernel works, you can revert your /etc/pacman.conf to the default repositories or keep the snapshot references until you upgrade.

Downgrading with the downgrade AUR Package

An alternative approach is to install the downgrade script from the AUR (Arch User Repository). This tool simplifies finding and installing older package versions:

1. Install downgrade using your preferred AUR helper (e.g., yay -S downgrade).
2. Run sudo downgrade linux. You will see a list of available older kernel packages.
3. Select the version you want; the script will handle the installation and necessary steps.

The script also references archived packages, so you do not have to manually configure the Arch Linux Archive.

Preventing Pacman from Upgrading the Kernel

After downgrading, you may not want pacman to install the latest kernel automatically. You can add the following line to your /etc/pacman.conf:

IgnorePkg = linux linux-headers

This ensures Pacman skips those packages for system upgrades. Remember that ignoring kernel updates can expose you to unresolved security vulnerabilities. Use this measure as a temporary solution until you verify that future kernel versions address your current issue.

Updating GRUB

Thanks to Pacman hooks, Arch Linux automatically updates GRUB configurations or kernel packages when installed. If needed, you can manually regenerate the GRUB configuration with:

sudo grub-mkconfig -o /boot/grub/grub.cfg

Reboot and confirm that the downgraded kernel is available and working as expected.

Preventing Automatic Kernel Upgrades

One of the frustrations in downgrading kernels is having the system upgrade itself again. Each distribution offers a way to pin, exclude, or ignore packages to avoid automatic kernel updates.

Pinning Packages on Debian/Ubuntu

On Debian-based systems, you can pin a specific kernel version:

Create or edit a file in /etc/apt/preferences.d/, for example,

/etc/apt/preferences.d/pin-kernel:

Package: linux-image-5.4.0-104-generic

Pin: version 5.4.0-104-generic

Pin-Priority: 1001

Update your package list with sudo apt-get update. A pin priority above 1000 ensures APT does not replace this package, even if newer versions are available.

Excluding Kernel Packages on Fedora/CentOS

For Fedora or CentOS, add an exclude line in your dnf or yum configuration file:

exclude=kernel*

This means the package manager ignores any package that begins with “kernel” when performing upgrades. Remove or comment on this line if you ever want to upgrade your kernel.

Ignoring Packages on Arch Linux

As mentioned above, add the following to your /etc/pacman.conf:

IgnorePkg = linux linux-headers

This ensures that pacman does not automatically update those packages. Remove or comment on this line later if you decide to upgrade.

Common Pitfalls and Troubleshooting Tips

Kernel downgrades can be tricky. Below are common pitfalls and suggested solutions to help you manage potential hurdles.

Unbootable System

If a newly installed older kernel fails to boot, you might face a situation where the system cannot start. Possible causes include missing bootloader entries, corrupted GRUB configurations, or missing drivers. To resolve this:

• Boot from a Live USB environment.
• Mount your system partitions.
• Use chroot to install or remove kernel packages or to fix GRUB.
• Reinstall or reconfigure GRUB if needed.

Missing Modules or Headers

Proprietary drivers (e.g., NVIDIA) or VirtualBox often require kernel headers for module compilation. If you installed only the kernel image without the headers, functionality might break. Install or downgrade the headers as well:

sudo apt-get install linux-headers-<version>
sudo dnf install kernel-headers-<version>

Make sure the version number matches your downgraded kernel.

Dependency Conflicts

Specific packages rely on newer kernel features. Check for messages about broken dependencies or attempts to remove essential software. If conflicts arise, you may need to temporarily remove or downgrade those packages. Document every change carefully so you can revert if necessary.

Signature Verification Errors

If your system does not recognize the package signature when manually downloading and installing packages, you may see errors. Update your distribution’s keyrings or import the GPG keys associated with that package. Using official or well-known repository archives reduces the likelihood of encountering signature issues.

SELinux and Security Modules

If you are running SELinux (common on Fedora, CentOS, and RHEL) or AppArmor (common on Ubuntu), issues with labeling or permissions might pop up after a kernel downgrade. Temporarily disabling SELinux or AppArmor can help you isolate the problem. Then, once your downgraded kernel is functioning, re-enable your security modules to preserve system protection.

Best Practices for Downgrading the Linux Kernel

Downgrading the kernel is best approached methodically. Below are a few tips to reduce your risks:

Always Maintain Backups

Back up critical data, system configurations, and the entire operating system or a disk image. Should anything go awry, you can revert quickly without losing important information.

Keep Multiple Kernels Installed

Avoid removing every other kernel version. Multiple kernels ensure you can quickly switch if the newly installed older kernel does not fix your issue or introduce new problems. This approach is critical on servers that cannot tolerate extended downtime.

Install Matching Headers and Modules

If you rely on proprietary drivers or use virtualization software, ensure that headers and kernel modules align with your chosen kernel version. Mismatched kernel and header versions can lead to failed module builds.

Use Official or Trusted Sources

Whenever possible, downgrade using official repositories or archives for your distribution. If you must install a kernel manually, only download from trusted sources to minimize the risk of installing compromised or incompatible software.

Test Thoroughly

After you downgrade, thoroughly test hardware drivers, network connectivity, and software applications. Scan system logs (/var/log/syslog, dmesg, journalctl) for errors or warnings. This diligence helps confirm that the system runs stably under the older kernel.

Document Every Step

Keep notes or a script of the commands you use, which packages you install or remove, and any modifications to configuration files. This documentation helps you remember what you did and aids others who may need to replicate or reverse your process in a team environment.

Plan Future Upgrades

While downgrading might solve your immediate problems, it is wise to monitor new kernel releases. A better-maintained kernel often means crucial security updates and performance improvements. Monitor distribution channels, bug trackers, or relevant mailing lists so you can upgrade confidently once a fix or stable release is available.

Conclusion

Downgrading the Linux kernel is critical for those who manage or rely on Linux systems in high-stakes environments. Despite its challenges, reverting to a previous kernel can restore functionality, stability, and performance when newer releases introduce unexpected issues. By carefully planning your downgrade process, backing up essential data, verifying dependencies, installing matching headers, and updating your bootloader, you can mitigate risks and seamlessly roll back your kernel.

Throughout this guide, you have learned:

• Why you might choose to downgrade your kernel, such as driver incompatibilities or performance issues.
• Before initiating the downgrade, what considerations should be considered, including data backups and potential security implications?
• How do you identify your current kernel version and select a suitable older version?
• Specific steps for downgrading on major distributions like Ubuntu, Debian, Fedora, CentOS, and Arch Linux.
• Methods to prevent automatic kernel updates, ensuring that your system stays on the desired version until you are ready to upgrade again.
• Common pitfalls and troubleshooting tips include unbootable systems, missing modules, or dependency conflicts.
• Best practices include maintaining multiple kernels, thoroughly testing, and staying informed about future updates.

Downgrading is temporary, giving you time to await a patched release of the newer kernel or plan a better upgrade path. Keeping your Linux system secure and stable is always paramount, and staying current with patches and updates should remain a long-term objective.

By applying the knowledge provided here, you will be better prepared to navigate kernel downgrades effectively and confidently. Whether you are fine-tuning a development environment, ensuring uptime on production servers, or simply exploring the deep layers of Linux, learning how to revert to an older kernel is an invaluable addition to your system administration skill set. With the proper preparations, best practices, and patience, kernel downgrading can be a smooth, controlled process, enabling you to keep your systems running at their optimum stability and performance level.

About the writer

Vinayak Baranwal wrote this article. Use the provided link to connect with Vinayak on LinkedIn for more insightful content or collaboration opportunities