I cannot find any Mabox-specific packages that would be updating grub to boot into the latest installed kernel after a system update, so I’ve asked the Manjaro folks this as well:
Anyone have any idea why, after a system upgrade and reboot, grub will boot the latest kernel version I have installed, whether or not I was using it before the update? Right now I have 5.4 and 5.10 installed, and I have been running 5.4. After an update/reboot, if I don’t get to the grub menu before it disappears, it will boot into 5.10.
I have looked at the grub pacman hook but cannot find any reason to believe it would be resetting GRUB_DEFAULT, for instance–it just runs update-grub, and /etc/defaults/grub is unchanged (I may get a .pacnew, but my old configs stay put). And I have poked into all the grub dirs I can find under /etc or /usr, but nothing is obviously causing this.
I don’t know grub well enough to know where else to look for the answer. I can live with it: it is not massively annoying to check if I am still running the kernel I was yesterday and to reboot if not.
But it is annoying enough for me to want to change this behavior. Anyone know why/how it happens?
Maybe for your situation solution will be pacman hook which will modify GRUB_DEFAULT option to point wished kernel. Alternatively you can use grub-set-default command. Look into Grub documentation to see how these options works