[jeroenhd]

I've used this command to achieve that in the past:

    sudo systemd-nspawn --directory=/ --read-only --ephemeral --volatile=yes

[systemd-nspawn](https://man7.org/linux/man-pages/man1/systemd-nspawn.1.html) would normally be used to run a command inside of a container (a directory), but in some modes you can specify the system root as the "container" path.

I believe this specific set of options relies on (BTRFS) file system snapshots for performance. It's possible that you can get it to work on non-BTRFS systems by providing another combination of command line variables, but the default setting is to copy the file system tree to a temporary path.

You can also pass parameters like --volatile=state (so you can write to /var) and --volatile=overlay (so you can "write" to state, but all changes are discarded after the container exits). --volatile=state is useful for extracting data from a temporary read-only system, --volatile=overlay is useful for running tools that crash if they run on a read-only filesystem.

[ronsor]

> I believe this specific set of options relies on (BTRFS) file system snapshots for performance. It's possible that you can get it to work on non-BTRFS systems by providing another combination of command line variables, but the default setting is to copy the file system tree to a temporary path.

You can use overlayfs + chroot.

[ape4]

--read-only would be a nice option for `run0`