systemd-volatile-root.service, systemd-volatile-root - Make the root file system
systemd-volatile-root.service is a service that replaces the root directory with
a volatile memory file system ("tmpfs"), mounting the original
(non-volatile) /usr inside it read-only. This way, vendor data from /usr is
available as usual, but all configuration data in /etc, all state data in /var
and all other resources stored directly under the root directory are reset on
boot and lost at shutdown, enabling fully stateless systems.
This service is only enabled if full volatile mode is selected, for example by
specifying "systemd.volatile=yes" on the kernel command line. This
service runs only in the initial RAM disk ("initrd"), before the
system transitions to the host's root directory. Note that this service is not
used if "systemd.volatile=state" is used, as in that mode the root
directory is non-volatile.