Home Assistant addon crashes on startup with NullPointerException in CgroupV2Subsystem (bare-metal cgroupv2 kernel)

Problem

The CompreFace Home Assistant addon enters a crash loop on startup with the following error:

java.lang.NullPointerException: null
    at java.base/jdk.internal.platform.cgroupv2.CgroupV2Subsystem.getInstance(CgroupV2Subsystem.java:81)

Environment: bare-metal x86/NUC running Home Assistant OS with a pure cgroupv2 kernel.

How to confirm: In the addon logs (HA → Settings → Add-ons → CompreFace → Log) you'll see Started FrsApplication immediately followed by Application run failed with the NPE above, repeating in a loop.

Root Cause

The JVM attempts to read the cgroup hierarchy via /sys/fs/cgroup/ and /proc/1/cgroup. On bare-metal systems with a pure cgroupv2 kernel, this fails with a NullPointerException in CgroupV2Subsystem.getInstance().

Fix

Two complementary fixes resolve the issue:

1. cgroup_fix.so (LD_PRELOAD) — a C library that intercepts open, open64, openat, fopen, fopen64 calls for /proc/1/cgroup and /proc/self/cgroup, returning fake cgroupv1 content (1:name=systemd:/)
2. -XX:-UseContainerSupport in a java_wrapper script — disables JVM container detection entirely, preventing CgroupV2Subsystem from being instantiated

Working Solution

I have published a corrected Docker image and full build instructions (Dockerfile, C source, java_wrapper script) here:

https://github.com/mdaraujoGit/compreface-fixed

The fixed image is available at ghcr.io/mdaraujogit/compreface-fixed:1.1.0 and can be used directly as a drop-in replacement for the original addon image.

Notes

• Related to issue #1291 (addon not starting in Home Assistant OS)
• Tested on Intel NUC, Home Assistant OS, OpenJDK 11, CompreFace 1.1.0