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Network Printer Drop-Print (Host CUPS Mode)

Quick start

version=$(cat ${PWD}/VERSION)
docker build -t registry.gitlab.com/tdmsa/service-printer:$version .

mkdir -p ${PWD}/printdrop

# Grant container access to the host CUPS socket's group
CUPS_GID=$(stat -c %g /run/cups/cups.sock)

docker run --rm \
  --name printer-service \
  --network=host \
  --user $(id -u):$(id -g) \
  --group-add ${CUPS_GID} \
  -e DISCOVERY_METHODS=cups,mdns \
  -e CUPS_SERVER=/run/cups/cups.sock \
  -v /run/cups/cups.sock:/run/cups/cups.sock \
  -v /etc/cups:/etc/cups:ro \
  -v ${PWD}/printdrop:/data/printers \
  registry.gitlab.com/tdmsa/service-printer:$version

Drop PDFs into /srv/printdrop/<queue_name>/. Each file is submitted to CUPS and then moved into /srv/printdrop/<queue_name>/archive/.

PRINTER_STATIC_JSON

  • If set, it explicitly controls which queues the container manages. Only those listed will get folders and be monitored. Format:
[
  { "name": "QueueA" },
  { "name": "HP_Color_LaserJet_M455_B94849" }
]
  • If not set, at startup the container will:
    • Discover available queues from CUPS,
    • Manage those queues,
    • Print a ready-to-copy PRINTER_STATIC_JSON suggestion to the logs so you can pin the set of managed queues and restart with it.

This makes it easy to lock down exactly which printers are used.

Environment variables

  • BASE_PATH=/data/printers
  • ARCHIVE_SUBDIR=archive
  • DISCOVERY_METHODS=cups,mdns (comma list: cups, mdns, static)
  • FILE_STABLE_SECONDS=2
  • PRINT_RETRY_COUNT=3
  • PRINT_RETRY_DELAY=5
  • INCLUDE_REGEX=
  • EXCLUDE_REGEX=
  • PRINTER_STATIC_JSON=
  • LOG_LEVEL=INFO
  • USE_PYCUPS=1
  • CREATE_MISSING=1
  • CUPS_SERVER=
    • Set to /run/cups/cups.sock to use the mounted host socket.
    • Or host:port to target remote CUPS directly.

Notes

  • Managing only CUPS queues by default avoids mDNS-only devices that are not set up as queues (which would fail). You can still keep mdns in discovery to aid future queue setup.
  • If you see “printer or class does not exist,” ensure:
    • You mounted the socket and added its group to the container (see quick start).
    • The queue exists in host CUPS (lpstat -p on host).
    • CUPS_SERVER is correct.

Troubleshooting

  • Permission denied on /data/printers: run with --user $(id -u):$(id -g) or chown/chmod the host directory for write access.
  • No queues discovered: verify CUPS is running; socket is mounted; container has the socket’s group; and CUPS_SERVER=/run/cups/cups.sock is set.
  • Jobs fail for statically listed queues: ensure the queue name exactly matches CUPS (lpstat -p), and that the container can reach CUPS.