Chapter 2. Specifying the RHEL kernel to run

Procedure

1. To configure kernel-rt as the default boot kernel, enter the following command:

   # grubby --set-default=<RT_VMLINUZ>

   RT_VMLINUZ is the name of the vmlinux file that is associated with the kernel-rt kernel. For example:

   # grubby --set-default=/boot/vmlinuz-6.12.0-284.11.1.rt14.296.el0_0_2.x86_64+rt

2. To configure kernel-rt as default boot kernel on system updates, enter the following command:

   # sed -i 's/UPDATEDEFAULT=.*/UPDATEDEFAULT=yes/g' /etc/sysconfig/kernel
   # sed -i 's/DEFAULTKERNEL=.*/DEFAULTKERNEL=kernel-rt-core/g' /etc/sysconfig/kernel

   The UPDATEDEFAULT variable when specified as yes, sets the default kernel to change with system updates.

   In the example output, the path for the default kernel is specific to the kernel-rt-core package installed. You can determine the path to the kernel from a package by using the rpm -q kernel-rt-core command.

   1. Optional: If you need to determine the path to the kernel from a package, first list the installed packages:

      # rpm -q kernel-rt-core
        kernel-rt-core-6.12.0-55.14.1.el10_0.x86_64
        kernel-rt-core-6.12.0-55.13.1.el10_0.x86_64
        kernel-rt-core-6.12.0-55.12.1.el10_0.x86_64

   2. To use the latest installed package as the default, enter the following command to find the path to the boot image from the package:

      # rpm -ql kernel-rt-core-6.12.0-55.14.1.el10_0.x86_64 | grep '^/boot/vmlinu'
      /boot/vmlinuz-6.12.0-55.14.1.el10_0.x86_64+rt

   3. To configure kernel-rt as the default boot kernel, enter the following command:

      # grubby --set-default=/boot/vmlinuz-6.12.0-55.14.1.el10_0.x86_64+rt