https://systemd.io/JOURNAL_FILE_FORMAT
+ * The interface for containers (https://systemd.io/CONTAINER_INTERFACE)
+ has been extended by a set of environment variables that expose
+ select fields from the host's os-release file to the container
+ payload. Similarly, host's os-release files can be mounted into the
+ container underneath /run/hosts. Together, those mechanisms provide a
+ standardized way to expose information about the host to the
+ container payload. Both interfaces are implemented in systemd-nspawn.
+
* All D-Bus services shipped in systemd now implement the generic
LogControl1 D-Bus API which allows clients to change log level +
target of the service during runtime.