One machine, Two systems (a dailydriver and a playground)

[Funkygoby]

Hello,

My mother is currently using Debian on her one and only laptop. She is kind of curious about understanding the system (cli, firewall) and already comfortable with apt udate/upgrade.
I would like to give her a "second" system she could play with and possibly break without consequence.

A spare machine is not possible, neither a 2nd harddrive. What would be possible options and which one would be the most practical (for me as the support and her as the user)? So far I am considering:
- VM: Install Debian in a qemu machine. I like qemu and have used it few time to test distros
- Docker. I started to use this at work. Maybe I could build an image, give it to her and then she could create a persistent container to play with? Spawn a new one when needed
- chroot and derivatives. I never used this but the simplicity of it is appealing (no service needed). Is it sufficient for my need ?

The guest's system needs to be separated from the host: trashing the guest's drive/network/root folder should not impact the host at all. I am not talking about bulletproof isolation, my mom won't exploit the kernel for escalation and such. All is needed here is enough separation for foot-shooting situations.

What are you thoughts on this?
Thanks

[Head_on_a_Stick]

Why not dual boot?

I use btrfs subvolumes to fit any number of distributions in a single partition. LVM can be used in a similar fashion with ext4 or xfs.