How to choose the correct kernel to boot on CloudLinux OS

Issue

In some cases, it's required to boot the server into a different kernel or switch it from the CentOS kernel to the CloudLinux kernel manually.

Environment

• CloudLinux OS

Solution

1. Check the current available kernels using the following command:

   # awk -F\' '$1=="menuentry " {print i++ " = "$2}' /etc/grub2.cfg

   You will see the output like below:

   0 = CloudLinux (3.10.0-962.3.2.lve1.5.54.el7.x86_64) 7.9 (Boris Yegorov)
   1 = CloudLinux (3.10.0-962.3.2.lve1.5.52.el7.x86_64) 7.9 (Boris Yegorov)
   2 = CentOS Linux (3.10.0-1160.21.1.el7.x86_64) 7 (Core)    

   Note:

   • The list may be different depending on the installed kernels on your server.
   • Please pay attention that the CloudLinux OS kernel contains the word 'LVE' in the name.
   • The position of a menu entry in the list is denoted by a number starting with zero, so we are numbering it especially in a correct way.

2. Select the desired kernel with the command below. Where 0 is the number from the kernel list obtained in step #1:

   # grub2-set-default 0

   Note: Please choose another number if you want to boot any other kernel from the list.

   !!! If you want to boot the CloudLinux kernel - please choose the kernel with 'lve' in the name.

3. Use the following command to check the currently selected kernel to be booted:

   # grub2-editenv list
   saved_entry=0 

Useful links

For more information about GRUB2 customization, refer to the official RedHat guide.