CentOS7-bootfix.md

1. Current Situation:

   • The system has multiple kernel versions installed:
     • 4.9.127-32.el7.x86_64 (newest)
     • 3.10.0-1160.11.1.el7.x86_64 (currently booting)
     • 3.10.0-957.21.3.el7.x86_64 (your preferred version)
     • Several debug kernels

2. The Issue:

   • The grubenv file shows that the system is set to boot into the debug version of 3.10.0-1160.11.1
   • This is likely happening because of the savedefault option in each menu entry, which saves the last booted entry as the default

3. Why It Changes:

   • When security updates install new kernels, they typically become the default boot option
   • The savedefault feature then remembers whatever kernel was last booted
   • If the system was ever booted into the debug kernel, it would remember that choice

4. To Fix This, you would need to run these commands on the remote system:

# To set the preferred kernel as default (957.21.3):
grub2-set-default "CentOS Linux (3.10.0-957.21.3.el7.x86_64) 7 (Core)"

# Verify the setting:
grub2-editenv list

# Regenerate the grub config:
grub2-mkconfig -o /boot/grub2/grub.cfg

5. To Prevent Future Issues:
   • Edit /etc/default/grub to set GRUB_SAVEDEFAULT=false
   • This will prevent the system from automatically changing the default kernel
   • Then regenerate the grub config again