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Dual Window Grub Bootloader
If Windows update overwrites the Grub bootloader. Simple way to restore is to copy the debian bootloader (grubx64.efi) over the windows bootloader. Open CMD prompt as “Administrator” and mount the EFT partition as E: drive with:
mountvol E: /S
E:\EFI>dir
Volume in drive E has no label.
Volume Serial Number is 502B-5BC6
Directory of E:\EFI
06-12-2016 20:05 <DIR> .
06-12-2016 20:05 <DIR> ..
06-12-2016 20:05 <DIR> Microsoft
13-02-2021 19:01 <DIR> Boot
27-11-2021 20:18 <DIR> HP
13-02-2021 08:35 <DIR> debian
0 File(s) 0 bytes
6 Dir(s) 160.800.768 bytes free
copy debian\grubx64.efi over Microsoft\Boot\bootmgfw.efi
BCDedit
C:\WINDOWS\system32>bcdedit
Windows Boot Manager
identifier {bootmgr} device partition=\Device\HarddiskVolume1 path \EFI\Microsoft\Boot\bootmgfw.efi description Windows Boot Manager locale nl-NL inherit {globalsettings} default {current} resumeobject {6beefd36-680a-11eb-ac07-a7444769703e} displayorder {current} toolsdisplayorder {memdiag} timeout 0
Windows Boot Loader
identifier {current} device partition=C: path \WINDOWS\system32\winload.efi description Windows 10 locale nl-NL inherit {bootloadersettings} recoverysequence {5c5834f8-aff6-11e9-ac26-ce270aa00281} displaymessageoverride Recovery recoveryenabled Yes isolatedcontext Yes allowedinmemorysettings 0x15000075 osdevice partition=C: systemroot \WINDOWS resumeobject {6beefd36-680a-11eb-ac07-a7444769703e} nx OptIn bootmenupolicy Standard
bcdedit /set {bootmgr} path \EFI\debian\grubx64.efi bcdedit /set {bootmgr} path \EFI\Microsoft\Boot\bootmgfw.efi
bcdedit /enum firmware bcdedit /timeout 10 bcdedit /copy {current} /d “Linux”
Windows Boot Manager
identifier {6beefd39-680a-11eb-ac07-a7444769703e} device partition=\Device\HarddiskVolume1 path \EFI\Microsoft\Boot\bootmgfw.efi description Linux locale nl-NL inherit {globalsettings} default {current} resumeobject {6beefd36-680a-11eb-ac07-a7444769703e} displayorder {current} toolsdisplayorder {memdiag} timeout 10