How to boot external disk with Linux Mint on UEFI Windows 10

[vlatomico]

Hello, dear community.
I want to perform a simple task, i want to boot Linux Mint from external SSD where it is alrdy installed.

I have preinstalled windows 10 in UEFI/GPT on HP notebook.
And I have installed Linux mint on external SSD disk probably in MBR/legacy that i was using before.
I realy dont want to reinstall or instal new linux to dual boot on notebook.
I just want to use both systems that i alrdy installed, bcs i have there a lot of installed aplications and data. My imagination was just to plug-in external disk and then boot linux when needed.

Secure Boot is disabled and there is no option for booting external device.
I tried to change UEFI to legacy in bios but there was warning :"Changing this setting may make the system unable to boot the os windows 10". So i rather did nothing.

Q: Changing this setting can corrupt instalation of windows where i cant go back?
I was not sure if i can just change UEFI to Legacy for booting Linux and then go back to UEFI and boot windows.

Thank you for reading and some sugestions.
Sincerely Vladimír.

 

[Alabalcho]

Vlad, you have three options:
- take out existing HDD/SSD from your laptop, switch over to Legacy, and see whether you can boot off your external HDD;
- make recovery Windows 10 bootable media (DVD/USB), and bite the bullet by performing above, back and forth, then repairing (or restoring) Windows installation;
- reinstall your Mint onto that same laptop, with UEFI/GPT scheme.

 

[vlatomico]

Taking out HDD is not an option right now, my notebook is still in varancy and sealed. And I dont see reinstall of OS as a solution.

But I am thinking about other option: changing Windows to MBR and change bios boot to legacy, it should be possible with easus app.


Q: And I still would like to know if changing boot mode to legacy is irreversible in a way where uefi windows cant be booted again without recovery.
If someone tried this or knows the answer please let me know.

Thank you for your answers and suggested options.