A server administrator recently installed a kernel update to test functionality Upon reboot, the administrator determined the new kernel was not compatible with certain server hardware and was unable to uninstall the update. Which of the following should the administrator do to mitigate further issues with the newly instated kernel version?

When a new kernel is installed, the bootloader (e.g., GRUB2) configuration is typically updated to make the new kernel the default boot option. If this new kernel is incompatible with the hardware, the most direct and least destructive method to resolve the issue is to change the bootloader's default entry back to the previous, known-good kernel. Editing the bootloader configuration file to modify the default stanza (the first entry) to load the older kernel files ensures the server boots into a stable state on subsequent restarts. This allows the administrator to keep the server operational while investigating the incompatibility.

B. A complete OS reinstall is an extreme measure that causes significant downtime and potential data loss. It is unnecessary for resolving a kernel boot issue when a previous working kernel is still available.
C. While moving the new kernel's stanza might result in the older kernel becoming the default, the more explicit and standard approach is to directly modify the default boot entry, as described in option A.
D. Setting a BIOS password is a physical and firmware-level security control. It has no impact on the operating system's kernel selection during the boot process and does not solve the software incompatibility. ---

1. Red Hat Enterprise Linux 8 Documentation, System Administrator's Guide. Chapter 26, "Working with the GRUB 2 boot loader," Section 26.5, "Changing the default boot entry." This official vendor documentation details the procedure for changing the default kernel for booting. It states, "To change the default operating system or kernel, you can modify the GRUB 2 configuration... by setting the GRUBDEFAULT option in the /etc/default/grub file." This aligns with the principle of modifying the bootloader configuration to select a known-good kernel.

2. GNU GRUB Manual 2.06. Section 5.1, "Simple configuration." The official manual for the GRUB bootloader explains the GRUBDEFAULT setting. It states, "This option sets the default menu entry. A value of ‘0’ sets the first menu entry as the default..." This confirms that the first entry is the default and that its target can be changed to control which kernel boots.

3. University of California, Berkeley, EECS Course CS162: Operating Systems and System Programming. Lecture 18, "File Systems & Booting." Course materials often describe the boot sequence, where the bootloader (like GRUB) reads a configuration file to present a menu of kernels and loads the default one if there is no user interaction. This foundational knowledge supports the solution of editing this configuration to change the default. (Example courseware structure, specific content may vary by semester).