Problem: Qubes OS entry disappeared from the boot menu.
I had installed Qubes concurrent with a Windows 10 installation and another Linux and the boot menu listed all 3. Everything worked fine. But one day I took out the drive, put in another and booted from that, and then put the original drive back in. From then on, the boot menu only had Windows and the other Linux, but Qubes OS had mysteriously disappeared. No software was installed during this time.
I was able to follow the ‘Installation finished but “Qubes” boot option is missing and xen.cfg is empty’ troubleshooting instructions to recreate a Qubes entry.
But I’m puzzled as to what could make the entry disappear in the first place and what can be done to prevent it?