After updating a server, rebooting it to load the new Kernel, removing the old Kernel and rebooting again, I got the GRUB minimal BASH-like prompt (I still can’t understand why, honestly), as if GRUB wasn’t able to see any info on how it should load the Kernel and the OS.
I know I could be very distracted but deleting all the Kernels seemed a little too much so I tried to manually boot the Kernel.
First, I checked what GRUB could see:
grub> ls (hd0) (hd0,msdos1) (hd0,msdos2)
Listed the content of the disks to see what files were present and determine which one was the root filesystem:
grub> ls (hd0,1)/ lost+found/ vmlinuz-5.10.21-200... initramfs-5.10.21-200....img vmlinuz-0-rescue... initramfs-0-rescue....img
Set it as boot volume:
grub> root=(hd0,msdos1)
Loaded the Kernel image and RAM disk:
grub> linux /vmlinuz-5.10.21-200... root=/dev/sda1 grub> initrd initramfs-5.10.21-200....img
And finally booted the system:
grub> boot
Just in case, I also created a new GRUB config based on the currently running system:
grub2-mkconfig -o /boot/grub2/grub.cfg