In the transition to CentOS 8, Oracle Linux 8, and RHEL 8, many users have noticed that the traditional linux16 lines in the /boot/grub2/grub.cfg file have seemingly vanished. This change may leave users puzzled, especially those accustomed to previous versions of these distributions where linux16 was a familiar term in the GRUB configuration. Below, we will explore what these lines were, why they are no longer present, and how the boot process has evolved in these modern Linux distributions.
Original Scenario
The issue stems from the linux16 lines in the /boot/grub2/grub.cfg, which many users expect to see when configuring their boot settings. Here's an example of what these lines may have looked like in previous versions:
linux16 /vmlinuz-4.x.x.el8.x86_64 root=UUID=<UUID> ro
Why Are the linux16 Lines Gone?
Starting with CentOS 8, Oracle Linux 8, and RHEL 8, the bootloader configuration has shifted towards a more unified approach, primarily driven by the adoption of the GRUB2 bootloader. In earlier versions, linux16 was used to specify the Linux kernel image for 16-bit mode. However, the need for 16-bit mode has largely diminished with advancements in hardware and kernel support.
What Replaces linux16?
With this transition, the boot process now utilizes the linux line instead of linux16. The shift reflects modern hardware capabilities where 32-bit and 64-bit modes are the standard, allowing a more streamlined and simplified configuration. Instead of using a separate line for legacy compatibility, the new configurations are optimized for current systems.
Here’s an example of the updated line in the new GRUB configuration:
linux /vmlinuz-4.x.x.el8.x86_64 root=UUID=<UUID> ro
Boot Process Changes
- Unified Boot Entries: The removal of
linux16indicates that there is a single unified approach to defining boot entries. - Easier Management: This change simplifies GRUB configuration management, reducing complexity for users and administrators.
- Increased Compatibility: As hardware continues to evolve, maintaining legacy support (like 16-bit) may lead to potential compatibility issues and performance inefficiencies.
Implications for Users
For system administrators and end-users, this change offers both opportunities and challenges. While the simplification is beneficial, it may require some adjustment for those familiar with earlier configurations. Users should ensure they are familiar with the new configuration syntax when managing boot entries, especially when troubleshooting boot issues or customizing the boot process.
Practical Example of Customizing GRUB2
Here’s how to update GRUB2 settings if you need to modify kernel parameters in CentOS 8 or its derivatives:
-
Open a terminal and edit the GRUB configuration file:
sudo nano /etc/default/grub -
Modify the
GRUB_CMDLINE_LINUXline to add or change parameters. For example:GRUB_CMDLINE_LINUX="quiet splash rd.lvm=0" -
After saving changes, regenerate the GRUB configuration:
sudo grub2-mkconfig -o /boot/grub2/grub.cfg -
Reboot the system to apply changes.
Conclusion
The transition from linux16 to a more simplified GRUB2 configuration reflects the ongoing evolution of Linux distributions, catering to modern hardware and user needs. While users of CentOS 8, Oracle Linux 8, and RHEL 8 may initially feel lost without the familiar linux16 lines, this change ultimately contributes to a cleaner and more efficient boot process.
Useful Resources
For more information on managing GRUB2 in CentOS, Oracle Linux, or RHEL 8, consider the following resources:
By keeping these changes in mind and utilizing the resources available, users can adapt to the modernized boot processes within these distributions effectively.
