# UNO Q — Remote & Headless Access

The Linux side is a real networked computer, so you can work with the board without a monitor. Three complementary paths: **Network Mode** (App Lab GUI over LAN), **SSH** (terminal), and **`adb`** (over USB). For a workshop where students use their own laptops, combine Network Mode for the GUI and SSH for the terminal.

## Prerequisite: get the board on the network
The board must be on Wi-Fi (or Ethernet via dongle) and you need either its **IP** or its **mDNS hostname**. SSH is **enabled automatically** during the App Lab first-run setup once you configure a username, password, and Wi-Fi.

## Find the board's IP address
Open a terminal on the board (App Lab bottom-left `>_` icon, or a desktop terminal) and run:
```bash
ip addr show
```
Look under the **`wlan0`** interface (or `eth0` if using Ethernet) for the `inet` address.

## Network Mode (App Lab over the LAN)
- Run App Lab on your PC; boards discovered on the local network appear tagged **"Network."** Select yours and enter credentials — you now develop from your PC as if local.
- Discovery uses **mDNS** (Bonjour/zeroconf). The board advertises `<board-name>.local`.
- **Firewall/OS notes:**
  - Allow **UDP port 5353** (mDNS) through the firewall.
  - On Windows, approve the `mdns-discovery.exe` prompt from Windows Defender.
  - Reaching the board directly by browser, SSH, or raw IP does **not** guarantee it shows up in Network Mode — mDNS must be working for the App Lab discovery.

## SSH (terminal access)
Default Linux user is **`arduino`**. Connect with either the IP or the mDNS name:
```bash
ssh arduino@<BOARD_IP>          # e.g. ssh arduino@192.168.1.42
ssh arduino@<board-name>.local  # if mDNS resolves on your network
```
On first connect, accept the host-key fingerprint (`yes`) and enter the board password you set during setup.

For passwordless login, install your key the standard way:
```bash
ssh-copy-id arduino@<BOARD_IP>
```
(or append your public key to `~/.ssh/authorized_keys` on the board). After that, `ssh arduino@<BOARD_IP>` won't prompt for a password.

Once in over SSH you have the full board: `apt`, `systemctl` (e.g. manage `arduino-router`), the `arduino-app-cli`, the LED sysfs, etc.

## Copy files to the board
Use `scp` (or `rsync`) from your PC. Apps live in `~/ArduinoApps/` on the board:
```bash
mkdir -p ~/ArduinoApps/<project-name>              # (run on the board)
scp -r * arduino@<BOARD_IP>:~/ArduinoApps/<project-name>   # (run on your PC, from the project dir)
```
Then start/stop it remotely with the CLI (see setup reference):
```bash
arduino-app-cli app start ~/ArduinoApps/<project-name>
arduino-app-cli app logs  ~/ArduinoApps/<project-name>
arduino-app-cli app stop  ~/ArduinoApps/<project-name>
```

## `adb` (over USB, no network needed)
With the Linux host udev rules installed (see setup reference), the board also speaks `adb`:
```bash
adb devices     # confirm the board is attached
adb shell       # shell into the board over USB
```
Handy when Wi-Fi isn't configured yet, for first-time provisioning, or for recovery.

## Hardware serial console (last resort)
If the board won't boot or has no network, the **JCTL** debug UART gives the raw SoC console at **115200 bps, 1.8 V logic** (use a 1.8 V USB-TTL adapter — see hardware reference). It shows bootloader/kernel messages and offers a login prompt with your Linux credentials.

## Picking the right one
- **GUI development from your laptop** → Network Mode.
- **Scripting, service management, autostart, file transfer, headless control** → SSH (+ `scp`, `arduino-app-cli`).
- **No network yet / provisioning / recovery** → `adb` over USB.
- **Won't boot / diagnosing early startup** → 1.8 V hardware debug UART.