Generates a dedicated tunnel keypair during setup, prints public key
for operator to pre-stage on server, writes private key to SD card.
On first boot: installs autossh, writes bb-tunnel.service with
correct RemoteForward and reconnect settings. Zero network traffic
until operator initiates connection through the tunnel port.
- Add prompt_default() helper: shows defaults, accepts Enter to use them
- WiFi: default=n (skip), keeps passphrase prompt loop
- Root password: auto-generate with openssl, show in summary if used, operator can override
- SSH key: default=1 (generate new)
- Device ID: auto-generate bb-<8-char-uuid>
- Boot mode: default=1 (passive)
- VPN: default=1 (none)
- Hostname: NEW section with auto-generated node-<6-char-uuid> default
- Alerter: default=n (disabled)
- Download: use curl -L (no -f), verify file exists and >50MB
- Config summary: show hostname, mask password (show auto-generated clearly)
- Apply config: write BB_HOSTNAME to /etc/hostname and /etc/hosts
- No eval with user input: use printf -v for variable assignment
Cobra