I have installed Ubuntu and Linux Mint on separate partitions of a hard drive, with two other partitions to be mounted as
/boot (one for each), and during the installation I chose for each of the two distributions to install its boot loader to its
/boot partition. The idea was to have the two systems completely independent and to select between the two boot loaders through the laptop's UEFI Setup boot menu. I was also hoping to be able to make each boot loader see the other one.
After installing Ubuntu with its boot loader on
/dev/sda2, this boot loader automatically became the laptop's first boot choice. However, after installing Mint with its boot loader
/dev/sda4 something strange happened: not only its boot loader became the first boot choice, but Ubuntu's boot loader is no longer accessible through the boot menu and I found no way to include it back.
What's more, Mint's boot loader now is listed in UEFI boot menu as
ubuntu (P1: HFS128G39MNC-2300A). I am not completely sure, but I can imagine this was the entry for Ubuntu before installing Mint.
I started doubting for a moment that I might have installed Mint's boot loader by mistake on
/dev/sda2, overwriting the one from Ubuntu. However, I mounted and inspected both
/dev/sda4, and it looks like the GRUB menu for loading Mint is well on
/dev/sda4, and the GRUB menu for loading Ubuntu (the one I cannot access anymore) is on
How can this behavior be explained and fixed?