Add CUPS print server container for Brother HL-4150CDN

README.md

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+# Printserver
+
+A containerized CUPS print server that shares a **Brother HL-4150CDN** network
+printer over IPP and advertises it via AirPrint (mDNS/DNS-SD), so client
+devices can print without installing the Brother driver themselves.
+
+The container bundles:
+
+- CUPS (IPP/IPP Everywhere + web admin on port 631)
+- Avahi / DNS-SD for AirPrint discovery (UDP 5353)
+- The Brother HL-4150CDN LPR + CUPS wrapper drivers and 32-bit runtime libs
+
+## Layout
+
+| Path | Purpose |
+| --- | --- |
+| `Containerfile` | Image definition (Debian base, i386 multiarch, Brother driver install) |
+| `cupsd.conf` | Container CUPS configuration (listen on all interfaces, share printers) |
+| `entrypoint.sh` | Starts D-Bus, Avahi and CUPS, then registers the printer queue |
+| `assets/Brother HL-4150CDN/` | Brother driver `.deb` packages used at build time |
+
+## Prerequisites
+
+- Podman (or a compatible builder such as Docker/Buildah)
+- The printer reachable on the network, with a known IP address or hostname
+
+## Build
+
+Run from the repository root:
+
+```sh
+podman build -t printserver:latest .
+```
+
+On an arm64 host, build for x86_64 explicitly (the Brother binaries are i386
+and need an x86_64 target):
+
+```sh
+podman build --platform linux/amd64 -t printserver:latest .
+```
+
+The build installs the Brother LPR and CUPS wrapper packages from
+`assets/Brother HL-4150CDN/` and verifies that the PPD and filter are in place.
+
+## Run
+
+mDNS does not work through a normal container network, so use **host
+networking**:
+
+```sh
+podman run -d --name printserver \
+  --network host \
+  -e PRINTER_IP=192.168.1.50 \
+  -e PRINTER_NAME=HL-4150CDN \
+  printserver:latest
+```
+
+### Environment variables
+
+| Variable | Default | Description |
+| --- | --- | --- |
+| `PRINTER_IP` | *(empty)* | IP address / host name of the network printer. A device URI is derived from it (see `PRINTER_PROTOCOL`). |
+| `PRINTER_URI` | *(empty)* | Full device URI. Overrides `PRINTER_IP` when set. |
+| `PRINTER_PROTOCOL` | `lpd` | Protocol used with `PRINTER_IP`: `lpd`, `socket` or `ipp`. |
+| `PRINTER_NAME` | `HL4150CDN` | CUPS queue name. Also used as the name advertised via AirPrint/DNS-SD. |
+| `PRINTER_DESCRIPTION` | *(empty)* | CUPS printer description (`lpadmin -D`), shown in the CUPS web UI. |
+| `PPD_FILE` | `/usr/share/cups/model/brhl4150cdn.ppd` | PPD used for the queue. |
+
+No queue is created when neither `PRINTER_IP` nor `PRINTER_URI` is set.
+
+### Choosing the connection
+
+The HL-4150CDN is a network printer. Set `PRINTER_IP` and let the entrypoint
+build the URI:
+
+| `PRINTER_PROTOCOL` | Resulting URI |
+| --- | --- |
+| `lpd` (default) | `lpd://<ip>/binary_p1` — LPR/LPD, the URI Brother documents |
+| `socket` | `socket://<ip>:9100` — raw AppSocket/JetDirect |
+| `ipp` | `ipp://<ip>/ipp/print` |
+
+For example, a printer at `192.168.1.50` using LPD:
+
+```sh
+-e PRINTER_IP=192.168.1.50
+```
+
+Or specify the URI explicitly for full control:
+
+```sh
+-e PRINTER_URI=lpd://192.168.1.50/binary_p1
+```
+
+### Advertised name
+
+`PRINTER_NAME` is used as the CUPS queue name and as the name clients see in
+AirPrint discovery. To show a descriptive label in the CUPS web interface,
+set `PRINTER_DESCRIPTION` (this does not change the advertised name):
+
+```sh
+-e PRINTER_NAME=HL4150CDN -e PRINTER_DESCRIPTION="Brother HL-4150CDN (Office)"
+```
+
+## Verify
+
+Browse the CUPS web interface:
+
+```sh
+open http://localhost:631/            # printers
+open http://localhost:631/admin       # administration
+```
+
+From the host, or inside the container:
+
+```sh
+podman exec printserver lpstat -t                 # queues and status
+podman exec printserver lpstat -v HL4150CDN       # device URI
+podman exec printserver avahi-browse -rt _ipp._tcp   # mDNS advertisement
+```
+
+A print job can be submitted with:
+
+```sh
+podman exec printserver lp -d HL4150CDN /etc/hostname
+```
+
+On macOS/iOS the shared queue should appear in the printer list via AirPrint.
+
+## Notes and limitations
+
+- **Run on an x86_64 host.** The Brother driver binaries are 32-bit i386 ELF
+  executables. They run natively on an x86_64 kernel, but on arm64 hosts the
+  image can be built and the drivers installed while the filter cannot execute
+  without i386 emulation (for example qemu-user / binfmt).
+- **Host networking is required** for Avahi to send and receive mDNS traffic.
+  `-p 631:631` alone is enough for direct IPP access but not for AirPrint
+  discovery.
+- **Printer state is not persisted.** The queue is recreated on every start
+  from `PRINTER_URI`. To keep CUPS configuration across container replacement,
+  mount a volume over `/etc/cups`:
+
+  ```sh
+  -v printserver-cups:/etc/cups
+  ```
+- The Brother filter is a PostScript-based CUPS filter. AirPrint clients that
+  rely on driverless (URF) printing may not be able to use the queue; macOS
+  clients that can use the shared CUPS queue's PPD will work.
+- The Brother driver packages are 32-bit (i386); the image enables Debian's
+  i386 multiarch to provide `libc6:i386` and the `ld-linux.so.2` loader they
+  need.