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#1782·beszel

[Bug]: Root disk reports container overlay (10MB) instead of host filesystem when running on ZFS (TrueNAS)

Author: jboctorCreated Mar 1, 2026Updated Sep 7, 2026
Labelsbug

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  • I have read the Documentation
  • I have checked the Common Issues Guide and my problem was not mentioned there.
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Component

Agent

Problem Description

[Bug]: Root disk reports container overlay (10MB) instead of host filesystem when running on ZFS (TrueNAS)

Component: Agent

Agent version: 0.18.4

Deployment: Docker (on TrueNAS Scale 25.10)

Description

When running the containerized agent on TrueNAS Scale (which uses ZFS exclusively), the root disk always reports the container's own overlay filesystem (~10MB) instead of the host's actual boot drive. The FILESYSTEM env var has no effect because Disk partitions=[] is always empty inside the container — ZFS datasets don't appear in the standard partition detection path.

Extra filesystems mounted via /extra-filesystems/ work correctly and report accurate usage. The issue is only with the root/primary disk.

Root cause

TrueNAS Scale's root filesystem is a ZFS dataset (boot-pool/ROOT/25.10.0), not a traditional block partition. Inside a Docker container, the agent's partition detection returns an empty list because ZFS datasets aren't enumerated through the standard /proc filesystem paths the agent uses. Since no partitions are found, the FILESYSTEM env var has nothing to match against, and the agent falls back to the container's own / overlay.

Host df -h output (relevant lines)

boot-pool/ROOT/25.10.0       198G  105M  198G   1% /
mypool/dataset1               30T  2.2T   28T   8% /mnt/mypool/dataset1
mypool/dataset2               48T   21T   28T  43% /mnt/mypool/dataset2
mypool/dataset3               29T  664G   28T   3% /mnt/mypool/dataset3

Agent debug logs

DEBUG Disk partitions=[]
WARN Partition details not found filesystem="Boot Pool__nvme0n1"
WARN Root device not detected; root I/O disabled mountpoint=/

Extra filesystems are detected and report correctly:

DEBUG Extra FS data="map[dataset1:0x... dataset2:0x... nvme0n1:0x... dataset3:0x...]"
ExtraFsPct:map[dataset1:7.2 dataset2:42.11 nvme0n1:1.41 dataset3:2.29]

Docker compose (relevant parts)

yaml
services:
  beszel-agent:
    privileged: true
    container_name: beszel-agent
    image: henrygd/beszel-agent
    network_mode: host
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
      - /proc:/host/proc:ro
      - /sys:/host/sys:ro
      - ./beszel_agent_data:/var/lib/beszel-agent
      - /usr:/extra-filesystems/Boot Pool__nvme0n1:ro
      - /mnt/mypool/dataset1:/extra-filesystems/dataset1:ro
      - /mnt/mypool/dataset2:/extra-filesystems/dataset2:ro
      - /mnt/mypool/dataset3:/extra-filesystems/dataset3:ro
    environment:
      FILESYSTEM: "Boot Pool__nvme0n1"
      HOST_PROC: /host/proc
      HOST_SYS: /host/sys
      LOG_LEVEL: debug

What I've tried

Configuration Result
FILESYSTEM: /mnt/mypool ZFS parent dataset shows 0% (child dataset accounting)
FILESYSTEM: nvme0n1p3 Shows as extra FS, root still 10MB
FILESYSTEM: /extra-filesystems/nvme0n1p3 Root still 10MB
FILESYSTEM: /host-root with /:/host-root:ro Root still 10MB
FILESYSTEM: "Boot Pool__nvme0n1" Partition not found, root still 10MB

All approaches fail because Disk partitions=[] means FILESYSTEM has nothing to match.

Environment

  • TrueNAS Scale 25.10 (Debian-based, ZFS only)
  • Docker with ZFS storage driver
  • Beszel Agent 0.18.4 (container)
  • AMD Ryzen with 6x HDD + 1x NVMe

Expected Behavior

Expected behavior

The root disk should report the host's actual boot drive usage (105M / 198G) rather than the container's overlay filesystem (~10MB). The FILESYSTEM env var should be able to override the root disk source even when partition detection returns empty results.

Steps to Reproduce

Steps to reproduce

  1. Install TrueNAS Scale (or any ZFS-only Linux system)
  2. Deploy the beszel-agent as a Docker container with LOG_LEVEL=debug
  3. Observe that Disk partitions=[] in the agent logs
  4. Observe that the root disk reports ~10MB (the container overlay) instead of the host's boot drive
  5. Attempt to override with FILESYSTEM env var pointing to any value — root disk remains at ~10MB

OS / Architecture

linux/amd64 (agent & hub)

Beszel version

0.18.4

Installation method

Docker

Configuration

yaml

Hub Logs

json

Agent Logs

bash

Source: henrygd/beszel

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