# 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.