Configuring the Client to Boot from the New Kernel

You must configure the client to boot from the new kernel that you just installed. On Red Hat and CentOS based operating systems, this can be done with grubby. For distributions that do not have grubby, refer to the official OS documentation to ensure that the latest kernel is set for boot.

1. Identify the installed kernel from Installing the Latest Kernel on the Client. In this example we will assume it is kernel kernel-ml-5.4.11-1.el7.elrepo.x86_64. In your case, the kernel will be a newer and higher number.
2. Find the new kernel grub entry with the following command: $ grubby --info=ALL
3. Identify the new kernel index in the output list of the command above. In the following example, the new kernel has an index value of 0 because it is at the top of the list of available kernels.

index=0

kernel=/boot/kernel-ml-5.4.11-1.el7.elrepo.x86_64

args="ro crashkernel=auto rd.lvm.lv=CentOS_rack05-server67/root rd.lvm.lv=CentOS_rack05-server67/swap rhgb quiet LANG=en_US.UTF-8"

root=/dev/mapper/CentOS_rack05--server67-root

initrd=/boot/initramfs-kernel-ml-5.4.11-1.el7.elrepo.x86_64.img

title=CentOS Linux (kernel-ml-5.4.11-1.el7.elrepo.x86_64) 7 (Core)

index=1

kernel=/boot/vmlinuz-3.10.0-957.el7.x86_64

args="ro crashkernel=auto rd.lvm.lv=CentOS_rack05-server67/root rd.lvm.lv=CentOS_rack05-server67/swap rhgb quiet LANG=en_US.UTF-8"

root=/dev/mapper/CentOS_rack05--server67-root

initrd=/boot/initramfs-3.10.0-957.el7.x86_64.img

title=CentOS Linux (3.10.0-957.el7.x86_64) 7 (Core)

index=2

kernel=/boot/vmlinuz-0-rescue-9758554168974f5dbe0d6dac5a6ac621

args="ro crashkernel=auto rd.lvm.lv=CentOS_rack05-server67/root rd.lvm.lv=CentOS_rack05-server67/swap rhgb quiet"

root=/dev/mapper/CentOS_rack05--server67-root

initrd=/boot/initramfs-0-rescue-9758554168974f5dbe0d6dac5a6ac621.img

title=CentOS Linux (0-rescue-9758554168974f5dbe0d6dac5a6ac621) 7 (Core)

index=3

non linux entry

4. Use the following command to set the default kernel index value.

In this example, the new kernel grub entry index value number is 0. So we set the default index to 0. This will make the OS boot off of this kernel on the next boot.

$ grubby --set-default-index 0

5. Verify the correct kernel version is set. $ grubby --default-kernel /boot/kernel-ml-5.4.11-1.el7.elrepo.x86_64

6. Reboot the system to load the Lightbits kernel. $ shutdown -r now

7. After the client reboots, you must log in and verify that the client is now running from the new kernel using the Linux command uname -r. For example: $ uname -r kernel-ml-5.4.11-1.el7.elrepo.x86_64