But you can't do that on a live system as you can with Windows or macOS. Not a problem for pre release upgrade perhaps. But I'm so missing this feature from macOS.
You can if you're using LVM. Take a snapshot of the logical volume your system is on, then run `dd' against the snapshot, as it's essentially a frozen point-in-time.
I've used this trick many times in a live, rw environment.
Depends on your filesystem. For example, I certainly can as I’m using btrfs. I’m also using Timeshift for easy management of snapshots. As others have mentioned, there are other choices too like Snapper that all work well.
I've used this trick many times in a live, rw environment.