From 4a05010532564ef4d6c6f435bf029eacdf13b5f6 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@amutable.com>
Date: Fri, 29 May 2026 18:31:17 +0200
Subject: [PATCH] rules: auto-tag host from the SYSTEMD_MACHINE_TAG udev
 property

When a device carries a SYSTEMD_MACHINE_TAG udev property, tag it for
systemd and pull in systemd-machine-tag@<tag>.service, which adds the
given tag to the host's machine tags. In other words, attaching the
property to a device makes the host auto-tag itself with the specified
machine tag.
---
 rules.d/99-systemd.rules.in | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/rules.d/99-systemd.rules.in b/rules.d/99-systemd.rules.in
index 98f483503e..0dfed01dfd 100644
--- a/rules.d/99-systemd.rules.in
+++ b/rules.d/99-systemd.rules.in
@@ -95,4 +95,7 @@ SUBSYSTEM=="tpm", KERNEL=="tpm[0-9]*", TAG+="systemd"
 SUBSYSTEM=="block", ENV{ID_PART_GPT_AUTO_ROOT_DISK_NEEDS_LOOP}=="1", \
   ENV{SYSTEMD_WANTS}+="systemd-loop@.service"
 
+# A device carrying the SYSTEMD_MACHINE_TAG property auto-tags the host with the specified machine tag.
+ENV{SYSTEMD_MACHINE_TAG}=="?*", TAG+="systemd", ENV{SYSTEMD_WANTS}+="systemd-machine-tag@$env{SYSTEMD_MACHINE_TAG}.service"
+
 LABEL="systemd_end"