man: encourage the creation of empty machine-id instead of deleting it

Current text hints that machine-id in template image should be empty
if the system is read-only. But most of the bare metal systems and
regular VMs have /etc read-only at this phase of boot.

(cherry picked from commit 64fcb07199f8409a074575eda5abb69b0caab06f)
(cherry picked from commit 5f55879673b119ebc98280518a9ab5bb7f4b1c5d)

diff --git a/man/machine-id.xml b/man/machine-id.xml
index b142d2f0b5d49a85be6b63935dba96a19daf9761..04676ab382090bc749ab76a49ed189c4f2ad5f4c 100644 (file)
--- a/man/machine-id.xml
+++ b/man/machine-id.xml
@@ -84,9 +84,9 @@
     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>
+    empty file in place is recommended because it allows a temporary file to be bind-mounted over the real file,
+    in case the image is used read-only and when <filename>/etc</filename> is mounted read-only in the early boot.
+    Also see <ulink url="https://systemd.io/BUILDING_IMAGES">Safely Building Images</ulink>.</para>
 
     <para><citerefentry><refentrytitle>systemd-firstboot</refentrytitle><manvolnum>1</manvolnum></citerefentry>
     may be used to initialize <filename>/etc/machine-id</filename> on mounted (but not