Systemd 254 - now with soft-reboot

Systemd 254 released and now has a new soft-reboot option:

<span style="color:#323232;">    * A new "soft-reboot" mechanism has been added to the service manager.
</span><span style="color:#323232;">      A "soft reboot" is similar to a regular reboot, except that it
</span><span style="color:#323232;">      affects userspace only: the service manager shuts down any running
</span><span style="color:#323232;">      services and other units, then optionally switches into a new root
</span><span style="color:#323232;">      file system (mounted to /run/nextroot/), and then passes control to a
</span><span style="color:#323232;">      systemd instance in the new file system which then starts the system
</span><span style="color:#323232;">      up again. The kernel is not rebooted and neither is the hardware,
</span><span style="color:#323232;">      firmware or boot loader. This provides a fast, lightweight mechanism
</span><span style="color:#323232;">      to quickly reset or update userspace, without the latency that a full
</span><span style="color:#323232;">      system reset involves. Moreover, open file descriptors may be passed
</span><span style="color:#323232;">      across the soft reboot into the new system where they will be passed
</span><span style="color:#323232;">      back to the originating services. This allows pinning resources
</span><span style="color:#323232;">      across the reboot, thus minimizing grey-out time further. This new
</span><span style="color:#323232;">      reboot mechanism is accessible via the new "systemctl soft-reboot"
</span><span style="color:#323232;">      command.>
</span>