Why isn't the serial port accessible under Trixie?

General
1

I have installed Trixie on one of my Pi’s, but I have problems with a serial device. Docker info:

docker info
Client: Docker Engine - Community
 Version:    29.6.1
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc.)
    Version:  v0.35.0
    Path:     /usr/libexec/docker/cli-plugins/docker-buildx
  compose: Docker Compose (Docker Inc.)
    Version:  v5.3.1
    Path:     /usr/libexec/docker/cli-plugins/docker-compose
  model: Docker Model Runner (Docker Inc.)
    Version:  v1.2.6
    Path:     /usr/libexec/docker/cli-plugins/docker-model

Server:
 Containers: 3
  Running: 1
  Paused: 0
  Stopped: 2
 Images: 4
 Server Version: 29.6.1
 Storage Driver: overlayfs
  driver-type: io.containerd.snapshotter.v1
 Logging Driver: json-file
 Cgroup Driver: systemd
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
 CDI spec directories:
  /etc/cdi
  /var/run/cdi
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 11ce9d5f3c68c941867e82890e93e815c1304f1b
 runc version: v1.3.6-0-g491b69ba
 init version: de40ad0
 Security Options:
  seccomp
   Profile: builtin
  cgroupns
 Kernel Version: 6.18.34+rpt-rpi-2712
 Operating System: Debian GNU/Linux 13 (trixie)
 OSType: linux
 Architecture: aarch64
 CPUs: 4
 Total Memory: 3.954GiB
 Name: Hytte-Pi
 ID: fa911361-5cf0-4d19-b9e5-951f0ad56190
 Docker Root Dir: /media/pi/Docker/Docker-System
 Debug Mode: false
 Experimental: false
 Insecure Registries:
  ::1/128
  127.0.0.0/8
 Live Restore Enabled: false
 Firewall Backend: iptables
  EnableUserlandProxy: true
  UserlandProxyPath: /usr/bin/docker-proxy

WARNING: No memory limit support
WARNING: No swap limit support

Docker compose file:

Docker compose file:

services:
  node-red:
    build:
      dockerfile_inline: | 
        FROM  nodered/node-red:4.0.9-debian
        USER root
        RUN apt-get update \
          && apt-get install -y --no-install-recommends iputils-ping sshpass openssh-client
        USER node-red
    container_name: Node-RED
    privileged: true
    restart: no
    group_add:
        - "20"
    environment:
      - TZ=Europe/Oslo

    network_mode: host 
    devices:
      - /dev/serial/by-id/usb-RFXCOM_RFXtrx433_A119M1VX-if00-port0:/dev/ttyUSB0
    volumes:
      - /media/pi/Docker/Docker-Compose/Node-RED/Data:/data
      - /media/pi/Docker/Docker-Compose:/home/pi/Docker-Compose:ro
      - /home/pi/.ssh/known_hosts:/usr/src/node-red/.ssh/known_hosts
      - type: bind
        source: /home/pi/Node-RED-omstarter.txt
        target: /home/pi/Node-RED-omstarter.txt
      - type: bind
        source: /home/pi/Z-Wave-omstarter.txt
        target: /home/pi/Z-Wave-omstarter.txt

Error message:

Node-RED  | 2026-07-10 21:29:48.895 [rfxcom] on /dev/ttyUSB0 - Error: Permission denied, cannot open /dev/ttyUSB0

I know the device is there, under the correct name. The pi user’s membership in the dialout group is working too. And two other serial devices in two other containers (two instances of Z-Wave JS UI for two different Z-Wave networks) are working. I am using the exact same Docker Compose files as I did under Bookworm, before installing Trixie from the ground up. Does anybody have a clue to why this is happening?

Edit: The command grep dialout /etc/group shows the same result in both: dialout:x:20:pi

2

Finally found it, I needed to add the group plugdev, 46, as well, for some reason. That was not necessary in the Bookworm setup, for some reason.