Why cAdvisor shows zero memory on Raspberry Pi 5 (ARM64 + cgroup v2)

Short answer: there are two separate causes, and most guides only cover the first. (1) Raspberry Pi OS ships with the memory cgroup controller disabled by default, so no tool can read container memory until you enable it. (2) Even after you enable it, cAdvisor still mis-reports container_memory_working_set_bytes on ARM64 + cgroup v2 — a known, unfixed upstream bug. Below: how to tell which one you're hitting, and how to fix both.

Layer 1 — memory cgroups are disabled by default

Out of the box, Raspberry Pi OS boots with the kernel's memory cgroup controller disabled. docker stats and every exporter (cAdvisor included) then read zero memory, because the kernel isn't accounting it.

Fix it by adding one flag to /boot/firmware/cmdline.txt (all on the existing single line) and rebooting:

cgroup_enable=memory

Use the current flag

Older (2022-era) tutorials tell you to add cgroup_memory=1 cgroup_enable=memory. On current Raspberry Pi OS, cgroup_enable=memory alone is correct — and cgroup v1 reporting was dropped entirely in Linux kernel 6.12+, so v2-only guidance now applies.

Confirm it took effect after reboot:

docker info | grep -i memory        # should NOT say "WARNING: No memory limit support"
cat /sys/fs/cgroup/memory.current   # a real number, not missing

This requirement is not going away. The Raspberry Pi kernel maintainers confirm memory cgroups are intentionally disabled by default and must be opted in (raspberrypi/linux#6980) — reconfirmed on the 2026 Raspberry Pi OS "Trixie" release (pi-gen#917). Enabling memory cgroups is a permanent step, not a temporary one.

Layer 2 — cAdvisor still gets it wrong on ARM64 + cgroup v2

Here's the part almost no article covers. After you enable memory cgroups, docker stats shows correct numbers — but cAdvisor still reports container_memory_working_set_bytes as zero on Raspberry Pi 5 (ARM64 + cgroup v2).

This is an upstream bug, not your configuration: cAdvisor #3469 — "Memory Usage always zero" (HW: Raspberry Pi 5) was closed "not planned" on 2025-12-09. A commenter who had already applied the cgroup_enable=memory fix still saw incorrect memory readings. Broader ARM-side pain is tracked in cAdvisor #2523. cAdvisor isn't sized or maintained for single-board ARM homelabs.

How to tell which layer you're at

Symptom	Cause	Fix
docker stats and cAdvisor both show zero memory	Layer 1 — cgroups disabled	Add cgroup_enable=memory, reboot
docker stats correct, but cAdvisor shows zero / wrong	Layer 2 — cAdvisor ARM64 bug	Use docker-exporter

The fix: read the stats API directly

docker-exporter sidesteps Layer 2 entirely. It reads the Docker stats API directly and computes the working set using the kernel's own definition:

• cgroup v2: usage − inactive_file
• cgroup v1: usage − cache

It uses the same metric name as cAdvisor (container_memory_working_set_bytes), so your Grafana panels light up again — with real numbers instead of zero. It runs in ~7 MiB of RAM (full footprint benchmark →), read-only on the socket, non-root.

docker run -d \
  --name docker-exporter \
  -v /var/run/docker.sock:/var/run/docker.sock:ro \
  -p 9713:9713 --restart unless-stopped \
  ghcr.io/dlepaux/docker-exporter:latest

Install guide → · docker-exporter vs cAdvisor →

FAQ

Why does cAdvisor show zero memory on a Raspberry Pi 5?

Two separate causes. First, Raspberry Pi OS ships with the memory cgroup controller disabled by default, so no tool can read container memory until you add cgroup_enable=memory to /boot/firmware/cmdline.txt and reboot. Second, even after that, cAdvisor still mis-reports container_memory_working_set_bytes on ARM64 with cgroup v2 — upstream bug #3469, closed "not planned".

What is the correct flag to enable memory cgroups on Raspberry Pi OS?

Add cgroup_enable=memory to /boot/firmware/cmdline.txt (on the existing single line) and reboot. The older cgroup_memory=1 cgroup_enable=memory form from 2022-era guides is no longer needed — cgroup_enable=memory alone is correct on current Raspberry Pi OS.

Will Raspberry Pi OS ever enable memory cgroups by default?

No. The Raspberry Pi kernel team has confirmed memory cgroups are intentionally available but disabled by default and must be opted into (raspberrypi/linux#6980). It's a deliberate, permanent decision, so the requirement is evergreen.

How do I fix cAdvisor's zero memory on ARM64?

If memory is still zero or wrong after enabling memory cgroups, it's cAdvisor bug #3469, not a config error. Use docker-exporter, which reads the Docker stats API directly and computes the working set correctly on cgroup v2 (usage − inactive_file).

Is this the same as the "No memory limit support" warning?

That warning is Layer 1 (cgroups disabled). Fix it with cgroup_enable=memory. If memory is still wrong after the warning is gone, you're at Layer 2.

Does enabling memory cgroups cost performance?

A small, fixed amount of kernel memory accounting overhead — negligible on a Pi 5, and required for any per-container memory metrics.

Why not just patch cAdvisor?

The upstream issue is closed "not planned," and cAdvisor's architecture walks the whole host/kernel/hardware topology by design — heavy for a single-board computer. A purpose-built exporter is the smaller, durable fix.