Easiest way to make an ephemeral VM (reboot to restore)?

[PAI5REECHO]

I'd like to be able to launch my VMs to use an in-memory disk or run in some way as to not commit any changes to my real drive

[Mic92]

Maybe you can use this? https://github.com/nix-community/impermanence

[Mic92]

Otherwise just delete nixos.qcow2 after each run.

[chrissound]

I'd like to be able to launch my VMs to use an in-memory disk or run in some way as to not commit any changes to my real drive

I think you can just run this from within a directory that is in a tmpfs/ramfs, so the file being written to is literally in ram. Maybe there would still be some overhead from needing to serialize the file though, but still would give you ephemeral functionality + likely fast IO performance.