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: <code> 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

<code>

copy debian\grubx64.efi over Microsoft\Boot\bootmgfw.efi

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