I finally found the cause, the two big hints were: - 2 fresh installs were in this order sda1, sda2 - only happens with install *without a reformat to sda1*
After the first install to sda1: - MBR (and MBR gap) contains GRUB core pointing to sda1, sda1 contains modules and config, this config on sda1 contains no os-prober entries as this was a fresh install After the second install to sda2: - MBR (and MBR gap) contains GRUB core pointing to sda2, sda2 contains modules and config, this config on sda2 now has os-prober entries for the install on sda1 - everything seems normal - sda1's grub config still doesnt contain os-prober entries, but it is dormant now After the third install *without reformat to sda1*: - MBR contains GRUB core again pointing to sda1, sda1 contains modules and config - while the installer regenerates the GRUB config here, during this re-generation the old config *on sda1* (due to no format) is checked for the presence of os-prober entries, and these won't appear in the dormant config from step 1, thus no new os-prober entries for the install on sda2 will be generated As a result sda1 was just a symptom and not the true cause, the true cause is overwriting an install with a dormant grub config containing no os-prober entries. The reason a no reformat re-install to sda2 didn't trigger is due to the existing grub config containing os-prober entries from step2. If the initial installs were in a different order, e.g. sda2 then after it sda1, then installing without reformat to sda2 will also trigger it. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2060624 Title: lubuntu/xubuntu reinstall (& install) on dual boot system, grub does appear & offer OS choice To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/2060624/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
