Booting windows 10 doesn't boot from external hard disk

I’m running KDE Plasma 5.23.4 on my internal hard drive and I need to boot Windows 10 from an external one.
The problem is it doesn’t appear as a boot option.
The disk is mounted and if I run fdisk -l, it appears.
I’ve manually inserted it the boot and it shows an error: sparse file not allowed. When I tried to fix that by changing /etc/default/grub, it says it doesn’t exist.
I’m kind of lost at this point and if anyone has any ideas, I’d be happy to try them.

To clarify first:

  • Your PC or laptop internal drive has Manjaro KDE Plasma installed (no other OSes like other GNU/Linux or Windows).
  • You have an external HDD/SSD/thumbdrive by USB connection that has live-Windows OS inside.

Also, when you said the external drive didn’t appear as a boot option, did you mean it didn’t show in the GRUB bootloader (the one you can see a list of OSes and you can choose one)?

I’m not sure what you were doing with the “/etc/default/grub” or if you try mounting the external drive to the /boot directory, but it’s better not to touch this for now or you risk make your system unbootable.

If you are booting from an external drive and you are not going to keep it connected all of the time, then you should just enter your bios/UEFI and select that drive to boot from in either override each time or if you can, you MAY be able to select that drive as the default boot option and the other drive as the fallback. This would depend on how your bios is set up.

You should leave grub out of it if you are disconnecting the drive at times, because I think it’ll erase the option when it doesn’t see it there.

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Windows 10 doesn’t doesn’t boot from External Drives.

First and foremost - this is not the place to seek advise on adding foreign systems to a Manjaro installation.

Secondly - from my bag of knowledge (admitting I may not be completely updated on Windows) I recall that Windows is not designed to install onto a removable media. The windows installer leaves out removable devices much like Calamares for Manjaro.

Closing as off topic for the Manjaro forum.

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