I have set up a dual boot in my laptop two months ago, and it has worked fine until recently, when the Windows 10 entry in GRUB menu has disappeared. It happened after a Windows update, but I don’t know how to get it back.
If I run sudo update-grub I get
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-5.10-x86_64
Found initrd image: /boot/intel-ucode.img /boot/initramfs-5.10-x86_64.img
Found initrd fallback image: /boot/initramfs-5.10-x86_64-fallback.img
Found linux image: /boot/vmlinuz-5.4-x86_64
Found initrd image: /boot/intel-ucode.img /boot/initramfs-5.4-x86_64.img
Found initrd fallback image: /boot/initramfs-5.4-x86_64-fallback.img
Warning: os-prober will not be executed to detect other bootable partitions.
Systems on them will not be added to the GRUB boot configuration.
Check GRUB_DISABLE_OS_PROBER documentation entry.
Adding boot menu entry for UEFI Firmware Settings ...
Found memtest86+ image: /boot/memtest86+/memtest.bin
I think the key is the error message os-prober will not be executed to detect other bootable partitions. Systems on them will not be added to the GRUB boot configuration. Check GRUB_DISABLE_OS_PROBER documentation entry.
os-prober seems to detect the Windows boot normally:
Grub got some needed security updates . Note that os-prober is now disabled by default for security reasons: broken patch ; fixed patch . More infos about it here . To restore the old behavior, open a terminal and issue sudo echo GRUB_DISABLE_OS_PROBER=false >> /etc/default/grub && sudo update-grub