From df41db03779d7aaebc0982c6ae74c7a604fb07d5 Mon Sep 17 00:00:00 2001
From: Adrian Vladu <avladu@cloudbasesolutions.com>
Date: Thu, 24 Oct 2024 14:37:06 +0000
Subject: [PATCH] cgroupv1: abort the update if Flatcar version does not
 support it

See: https://github.com/systemd/systemd/releases/tag/v256-rc3
See: https://github.com/flatcar/scripts/pull/2145
---
 flatcar-postinst | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/flatcar-postinst b/flatcar-postinst
index 5ee639a..2277d82 100644
--- a/flatcar-postinst
+++ b/flatcar-postinst
@@ -244,6 +244,14 @@ if mountpoint -q /etc; then
   unshare -m sh -c "umount /etc && mkdir -p /etc/extensions && attr -R -r overlay.opaque /etc/extensions || true"
 fi
 
+# Systemd version >= 256 does not boot anymore if cgroupv1 is enabled or SYSTEMD_CGROUP_ENABLE_LEGACY_FORCE=1 is set
+# See: https://github.com/systemd/systemd/releases/tag/v256-rc3
+NO_CGROUPV1_VERSION_ID=5000
+if [ ! -f "/sys/fs/cgroup/cgroup.controllers" ]; then
+    echo "Flatcar version ${NO_CGROUPV1_VERSION_ID} or higher does not support cgroupv1 anymore. Aborting the update..." >&2
+    exit 1
+fi
+
 # Keep old nodes on cgroup v1
 if [[ "${BUILD_ID}" != "dev-"* ]]; then
     if [ "${VERSION_ID%%.*}" -lt 2956 ]; then