printserver/entrypoint.sh

#!/bin/sh
# Startup script for the containerized CUPS print server.
#
# Starts the D-Bus system bus, Avahi (mDNS/DNS-SD) and CUPS, then registers
# the Brother HL-4150CDN queue if it does not exist yet. The CUPS daemon is
# kept in the foreground so the container lives as long as the print server.
#
# The queue uses Brother's BR-Script3 (PostScript 3) PPD and, by default,
# sends jobs to the printer over raw AppSocket (socket://<ip>:9100). CUPS
# converts client documents to PostScript and the PPD turns device options
# (tray, duplex, colour, ...) into PostScript "setpagedevice" instructions.
#
# Configuration (all optional, via environment):
#   PRINTER_IP           IP address / host name of the network printer.
#   PRINTER_URI          Full device URI; overrides PRINTER_IP when set.
#   PRINTER_PROTOCOL     socket (default), lpd or ipp - used with PRINTER_IP.
#   PRINTER_NAME         CUPS queue name and advertised (DNS-SD) name.
#   PRINTER_DESCRIPTION  CUPS Description (lpadmin -D) shown in the web UI.
#   PPD_FILE             PPD used for the queue.
set -eu

PRINTER_NAME="${PRINTER_NAME:-HL4150CDN}"
PRINTER_IP="${PRINTER_IP:-}"
PRINTER_URI="${PRINTER_URI:-}"
PRINTER_PROTOCOL="${PRINTER_PROTOCOL:-socket}"
PRINTER_DESCRIPTION="${PRINTER_DESCRIPTION:-}"
PPD_FILE="${PPD_FILE:-/usr/share/cups/model/BR4150_2.PPD}"

LOG_PREFIX="[entrypoint]"
log() { echo "${LOG_PREFIX} $*"; }

# Build a device URI from PRINTER_IP unless an explicit PRINTER_URI is given.
# Raw AppSocket is the default: the HL-4150CDN accepts PostScript directly on
# port 9100 (its BR-Script3 interpreter auto-detects the job language).
if [ -z "${PRINTER_URI}" ] && [ -n "${PRINTER_IP}" ]; then
    case "${PRINTER_PROTOCOL}" in
        socket)
            PRINTER_URI="socket://${PRINTER_IP}:9100"
            ;;
        lpd)
            PRINTER_URI="lpd://${PRINTER_IP}/binary_p1"
            ;;
        ipp)
            PRINTER_URI="ipp://${PRINTER_IP}/ipp/print"
            ;;
        *)
            log "unknown PRINTER_PROTOCOL '${PRINTER_PROTOCOL}', defaulting to socket"
            PRINTER_URI="socket://${PRINTER_IP}:9100"
            ;;
    esac
fi

# --- D-Bus system bus -------------------------------------------------------
mkdir -p /run/dbus /var/lib/dbus
if [ ! -s /etc/machine-id ] && [ ! -s /var/lib/dbus/machine-id ]; then
    log "generating D-Bus machine id"
    dbus-uuidgen > /var/lib/dbus/machine-id
fi
if [ ! -S /run/dbus/system_bus_socket ]; then
    log "starting dbus-daemon (system bus)"
    dbus-daemon --system --fork
fi

# --- Avahi / mDNS -----------------------------------------------------------
mkdir -p /run/avahi-daemon
if ! pgrep -x avahi-daemon >/dev/null 2>&1; then
    log "starting avahi-daemon"
    avahi-daemon --daemonize --no-chroot
fi

# --- CUPS -------------------------------------------------------------------
log "starting cupsd"
/usr/sbin/cupsd -f &
CUPSD_PID=$!

# Wait until CUPS accepts requests.
i=0
while [ "$i" -lt 30 ]; do
    if lpstat -r >/dev/null 2>&1; then
        break
    fi
    i=$((i + 1))
    sleep 0.5
done

# Share printers on the network and allow remote administration.
cupsctl --share-printers --remote-admin >/dev/null 2>&1 || true

# --- Brother HL-4150CDN queue ----------------------------------------------
if lpstat -p "${PRINTER_NAME}" >/dev/null 2>&1; then
    log "printer ${PRINTER_NAME} already exists"
elif [ -n "${PRINTER_URI}" ]; then
    if [ -f "${PPD_FILE}" ]; then
        log "adding printer ${PRINTER_NAME} -> ${PRINTER_URI}"
        lpadmin -p "${PRINTER_NAME}" -E -v "${PRINTER_URI}" -P "${PPD_FILE}" \
            || log "warning: lpadmin failed to add ${PRINTER_NAME}"
    else
        log "warning: PPD ${PPD_FILE} not found; skipping printer creation"
    fi
else
    log "neither PRINTER_URI nor PRINTER_IP is set; skipping automatic printer creation"
fi

# Make sure the queue is shared, named for advertising and set as default.
if lpstat -p "${PRINTER_NAME}" >/dev/null 2>&1; then
    lpadmin -p "${PRINTER_NAME}" -o printer-is-shared=true -E >/dev/null 2>&1 || true
    if [ -n "${PRINTER_DESCRIPTION}" ]; then
        lpadmin -p "${PRINTER_NAME}" -D "${PRINTER_DESCRIPTION}" >/dev/null 2>&1 || true
    fi
    lpadmin -d "${PRINTER_NAME}" >/dev/null 2>&1 || true
    log "queue ${PRINTER_NAME} is shared and set as default"
fi

# --- Verify CUPS is reachable on the network --------------------------------
# cupsd also runs with nothing but its domain socket, e.g. when it cannot bind
# the privileged port 631 (rootless Podman with host networking). It then still
# advertises the queue over mDNS, so clients see a printer they cannot reach.
# Detect that and fail loudly instead of reporting a healthy server.
if ! curl -fsS --noproxy '*' --max-time 2 -o /dev/null http://127.0.0.1:631/ 2>/dev/null; then
    log "ERROR: cupsd is not listening on TCP 631 - network clients (AirPrint/IPP) cannot reach this server"
    if [ -f /var/log/cups/error_log ]; then
        log "       recent CUPS errors:"
        tail -n 5 /var/log/cups/error_log | sed 's/^/         /'
    fi
    log "       If the log shows 'Unable to open listen socket for address 0.0.0.0:631 - Permission denied',"
    log "       port 631 is privileged and this rootless container may not bind it on the host network."
    log "       Either allow unprivileged binding of 631 (host, needs root), persistently:"
    log "         echo 'net.ipv4.ip_unprivileged_port_start=631' > /etc/sysctl.d/90-unprivileged-ports.conf"
    log "         sysctl --system"
    log "       or run this container as a rootful (system) service."
    log "       See the Troubleshooting section of the README."
    exit 1
fi

log "ready: CUPS on 631/tcp, mDNS on 5353/udp"

# Keep the container running by waiting on cupsd.
wait "${CUPSD_PID}"