- <para>For operating system images which are created once and used on multiple
- machines, for example for containers or in the cloud,
- <filename>/etc/machine-id</filename> should be either missing or an empty file in the generic file
- system image (the difference between the two options is described under "First Boot Semantics" below). An
- ID will be generated during boot and saved to this file if possible. Having an empty file in place is
- useful because it allows a temporary file to be bind-mounted over the real file, in case the image is
- used read-only.</para>
+ <para>For operating system images which are created once and used on multiple machines, for example for
+ containers or in the cloud, <filename>/etc/machine-id</filename> should be either missing or an empty
+ file in the generic file system image (the difference between the two options is described under "First
+ Boot Semantics" below). An ID will be generated during boot and saved to this file if possible. Having an
+ empty file in place is useful because it allows a temporary file to be bind-mounted over the real file,
+ in case the image is used read-only. Also see <ulink url="https://systemd.io/BUILDING_IMAGES">Safely
+ Building Images</ulink>.</para>