archiso/mkarchiso: write "uninitialized" to /etc/machine-id

This is a new value introduced in systemd v247. It makes sure a new
machine-id is generated, but is handled as first boot as well.

See "First Boot Semantics" in machine-id(5) for details.

2 files changed, 6 insertions, 2 deletions

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 4966b84..19a4d91 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -18,6 +18,9 @@ Changed
 - Error out early if any of the code signing certificate files passed with option ``-c`` do not exist.
 - Use LZMA compressed EROFS image for the baseline profile. Now that xz 5.4 is out and erofs-utils is built with LZMA
   support, using a higher compression is possible.
+- Add ``/etc/machine-id`` with special value ``uninitialized``. The final id is generated at boot time, and systemd's
+  first-boot mechanim (see ``First Boot Semantics`` in ``machine-id(5)``) applies. No functional change unless that
+  ``ConditionFirstBoot=yes`` is true and passive unit ``first-boot-complete.target`` activates for ordering.
 
 Removed
 -------
diff --git a/archiso/mkarchiso b/archiso/mkarchiso
index 8449f51..7331bb0 100755
--- a/archiso/mkarchiso
+++ b/archiso/mkarchiso
@@ -163,9 +163,10 @@ _cleanup_pacstrap_dir() {
     [[ -d "${pacstrap_dir}/var/tmp" ]] && find "${pacstrap_dir}/var/tmp" -mindepth 1 -delete
     # Delete package pacman related files.
     find "${work_dir}" \( -name '*.pacnew' -o -name '*.pacsave' -o -name '*.pacorig' \) -delete
-    # Create an empty /etc/machine-id
+    # Create /etc/machine-id with special value 'uninitialized': the final id is
+    # generated on first boot, systemd's first-boot mechanism applies (see machine-id(5))
     rm -f -- "${pacstrap_dir}/etc/machine-id"
-    printf '' > "${pacstrap_dir}/etc/machine-id"
+    printf 'uninitialized\n' > "${pacstrap_dir}/etc/machine-id"
 
     _msg_info "Done!"
 }