Container detection returns null on cgroups v2 / Debian 13

[joegharbi]

Environment

• OS: Debian 13
• cgroups: v2 (cgroup2fs)
• Docker version: 29.2.1, build a5c7197
• Scaphandre version: 1.0.2

Problem

With scaphandre json --containers -f output.json, all consumers have container: null in the JSON output. The same workflow worked on Debian 12.

Cgroup path example

Container processes have cgroup paths like:
0::/system.slice/docker-cb6970b7e0a606b4d7d25f4f0ef37a51efcd99a57c56d95c0a70bf645151bcd8.scope

Steps to reproduce

1. Run a Docker container: docker run -d --name test-container
2. Run Scaphandre: sudo scaphandre json --containers -f output.json (let it run a few seconds, then Ctrl+C)
3. Inspect output: jq '.[0].consumers[:3]' output.json
4. Observe: all consumers have "container": null

Related

• Issue containers option does not work with Linux containers #257
• Same benchmark setup works with Scaphandre's container field on Debian 12