[Resolved] Safe way to boot test a clone of my internal drive?

I’m on Ubuntu 21.04 on my laptop. I’m regularly using Clonezilla to clone my main internal drive to an external USB connected nvme drive. I want to test boot from this external drive to make sure the clone is working good but somewhere I read to never plug in and try to boot from an external clone drive cuz that could mess up the main internal drive.

Is there a software way to disable/disconnect the main internal drive so I can safely boot from and test the external clone drive? I know I can open my laptop and physically remove the internal drive, but it sure would be easier if I could run some command to disable/disconnect the main internal drive.

Even though I’m a newbie I can see that in order to do this I’d have to boot from something like Magic Parted on a USB stick. And then run the hypothetical (mythical?) “disconnect/disable” command from the live Magic Parted instance.

Any way to do this? Thanks.

PS: I just had a thought. Is it possible to unmount the main internal drive from within Magic Parted? Then try the external drive boot test? Then get back in to Magic Parted and re-mount the internal drive?

tl;dr As a general rule choosing which drive to boot from and the boot order is handled by the BIOS settings and the system bootloader such as GRUB (GRand Unified Bootloader). You shouldn’t have any problems.

I’ve not heard of this problem on Linux – I have had issues booting from a clone with Windose. Do you recall where you might have stumbled across this info? There must be a larger context that would help to explain this. FWIW booting from a USB device is a common route you take to FIX an internal drive. While nearly anything is possible, it’s not a great likelihood of doing damage.

Every time you power down the device, all drives are unmounted. Every time you power up the device, drives designated in /etc/fstab are auto mounted. Messing with /etc/fstab can get you in hot water: so backup, backup, backup and read man fstab three times before you try anything. Then test your fstab file with:

sudo mount -a
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The warning is on this page boot - Create bootable backup system image - Ask Ubuntu Search for this text:


  • Never boot the computer with both the original drive and a cloned copy of it connected at the same time. If you do that, there will be confusion because there are pairs of identical partitions and file systems, and the boot system may choose to use them and write to them in a way, that both get damaged, so that they will no longer work.
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Thanks for the details. As a newbie, it’s better for me not to mess with things like /etc/fstab that I know nothing about.

OK, thanks. So if I unmount the internal drive using Magic Parted, it will just remount when power comes back on. So my idea wouldn’t work. Well, the drive is easy to physically remove, so I may just do that once in a while to test.

Could you mark this thread as resolved? Thanks.

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