Another approach I miss from SmartOS.

It boots from a USB stick, loads system to a RAM disk, mounts configuration from a directory, and then hosts VM zones from ZFS datasets. The “root” system remains immutable.

To patch or upgrade, you just write a new system image to the USB stick and reboot. It’s great.

To skip the USB stick, you can do the whole thing over PXE.

After running a cluster on SmartOS for many years, moving back to Linux and installing the OS feels fragile, dirty, and weird.