I am not understanding how it comes to know which kernel image to load?
I have so many.
Once I had created my own kernel and recompiled.
How does it come to know that this is the one to load?
I am not understanding how it comes to know which kernel image to load?
I have so many.
Once I had created my own kernel and recompiled.
How does it come to know that this is the one to load?
To answer your final question:
You can put the new menuentry anywhere in /etc/grub.d/40_custom.
Then edit /etc/default/grub, and change the DEFAULT to the name of the menuentry that you added to 40_custom. (Using the name rather than a 0-indexed number is best because it allows for the possibility of more kernel images being added or deleted later: see grub2 infopage).
Then make sure to run sudo update-grub2
(or your changes won't be written to grub.cfg).
Reasoning: 40_custom gets added to grub menu underneath any kernel images that grub-update2 finds, so the order within 40_custom won't overide the kernels found by 10_linux.