Docker container loses access to port between prints

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What is the problem?

octoprint cannot connect to my printer on fresh boot, consistently.

More specifically, after I finish a print, I come back and try another (often days later), my octokit instance cannot connect to the serial port.

The "fix" is a plain container reboot on my pi (e.g. docker restart abc123). Here's my compose.yml:

version: '2.4'
services:
  octoprint:
    image: octoprint/octoprint
    restart: always #unless-stopped
    ports:
      - 80:80
    privileged: true
    devices:
      - /dev/ttyACM0:/dev/ttyACM0
      - /dev/ttyAMA10:/dev/ttyAMA10

What did you already try to solve it?

Compared the logs in the bad state (pre-restart), and the good state (post docker restart)

Bad:

2025-08-30 06:41:10,478 - octoprint.util.comm - INFO - Serial detection: Performing autodetection with 7 port/baudrate candidates: /dev/ttyACM0@115200, /dev/ttyACM0@250000, /dev/ttyACM0@230400, /dev/ttyACM0@57600, /dev/ttyACM0@38400, /dev/ttyACM0@19200, /dev/ttyACM0@9600
2025-08-30 06:41:10,479 - octoprint.util.comm - INFO - Serial detection: Trying port /dev/ttyACM0, baudrate 115200
2025-08-30 06:41:10,479 - octoprint.util.comm - INFO - Connecting to port /dev/ttyACM0, baudrate 115200
2025-08-30 06:41:10,481 - octoprint.util.comm - INFO - Failed to connect: Port /dev/ttyACM0 is busy or does not exist
...SNIP...
2025-08-30 06:41:10,502 - octoprint.util.comm - INFO - Changing monitoring state from "Detecting serial connection" to "Error"
2025-08-30 06:41:10,503 - octoprint.util.comm - INFO - Changing monitoring state from "Error" to "Offline after error"

Good:

2025-08-30 06:41:56,287 - octoprint.util.comm - INFO - Connecting to port /dev/ttyACM0, baudrate 115200
2025-08-30 06:41:56,295 - octoprint.util.comm - INFO - Serial detection: Handshake attempt #1 with timeout 2.0s
2025-08-30 06:41:56,297 - octoprint.util.comm - INFO - M110 detected, setting current line number to 0
2025-08-30 06:41:56,300 - octoprint.util.comm - INFO - Changing monitoring state from "Detecting serial connection" to "Operational"

Have you tried running in safe mode?

I haven't!

Did running in safe mode solve the problem?

I haven't!

Systeminfo Bundle

octoprint-systeminfo-20250830065930.zip (12.4 KB)

Additional information about your setup

  1. pi5
  2. Docker version 27.4.0, build bde2b89
  3. $ lsb_release -a
    Distributor ID: Ubuntu
    Description: Ubuntu 24.04.1 LTS
    Release: 24.04
    Codename: noble