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I messed around with bcdedit {bootmgr} and {fwbootmgr} on Windows, and now I cannot boot windows from the grub menu (it exists but just returns me to the grub menu).

In trying to deal with one of the 500 problems arising from this: imagine I don't know on which disk windows was installed. How do I find out?

Thanks

EDIT: It seems I can find out using sudo fdisk -l:

Disk /dev/sdb: 232.9 GiB, 250059350016 bytes, 488397168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 1AFAA023-DCDF-4E17-8F4F-535A544DA063

Device         Start       End   Sectors   Size Type
/dev/sdb1       2048    616447    614400   300M Windows recovery environment
/dev/sdb2     616448    819199    202752    99M EFI System
/dev/sdb3     819200   1081343    262144   128M Microsoft reserved
/dev/sdb4    1081344 486635411 485554068 231.5G Microsoft basic data
/dev/sdb5  486635520 488396799   1761280   860M Windows recovery environment

Ordinarily, I think a good idea for others would be to use sudo os-prober, but this returns nothing for me (probably because it's broken).

  • You can start with this command lsblk -o NAME,FSTYPE and look for NTFS partitions. – schrodigerscatcuriosity May 1 at 14:17
  • Or better sudo blkid | grep ntfs – schrodigerscatcuriosity May 1 at 14:30
  • Grub only boots working Windows. So if Windows did an update which you may not have seen, it may have turned fast start up back on. Then grub would not boot it. If UEFI, you should be able to directly boot from UEFI boot menu, same key you use to boot USB flash drive. Most Windows fixes need a Windows repair disk. Grub boots Windows files in ESP if UEFI or in Windows Boot partition if BIOS. – oldfred May 1 at 14:40
  • I updated the question. I found the windows partition, but os-prober doesn't find it (after reinstalling grub, there are no longer any windows options, oops). Thanks anyway, what I wanted to know was solved! – ricky116 May 1 at 14:47
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The Windows partition should be called (Windows SyS Drive) in Gnome Disks in Ubuntu!

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