Linux_post_install/DOC/howto/network.md

How-To: pos network

Networking day-to-day: IP/diagnostic info, Wi-Fi hotspots, host discovery, and port checks. Tools: ip, hotspot, scan, checkport.

Tool	What it does
pos network ip	Interfaces, default route, public IP + location
pos network hotspot	Wi-Fi AP via create_ap / wihotspot-gui
pos network scan	Two-phase host discovery with nmap
pos network checkport	Is a TCP port open on a host?

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pos network ip — where am I, what's my IP

pos network ip

Shows local interfaces + addresses, the default route, and your public IP with its geolocation. Useful before ssh-ing home or opening ports.

Recipe: public IP on the go — this is the same value the health digest includes, so if your home IP changed you'll see it in the 08:00 report.

Troubleshooting: the public-IP lookup needs outbound HTTPS; if it prints "unreachable"/location unknown, your network or a firewall is blocking api.ipify.org / the geo provider.

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pos network hotspot — turn the machine into a Wi-Fi AP

Requires the precompiled create_ap + wihotspot-gui binaries shipped in x64_bin/ (or arm64_bin/) and installed to /usr/local/bin by install.sh. The GUI needs a desktop session; the CLI needs a wireless NIC in AP mode.

pos network hotspot                       # launch the wihotspot-gui
pos network hotspot start wlan0 eth0 MyNet mypass      # AP on wlan0, internet via eth0
pos network hotspot start --foreground wlan0 eth0 MyNet mypass   # block until Ctrl+C
pos network hotspot stop                  # stop the running AP (auto-detected)
pos network hotspot stop wlan0            # stop by interface/PID
pos network hotspot status                # list running APs

Positional args: <wifi-iface> [<internet-iface>] <ssid> [<passphrase>]. Without --foreground, it asks whether to run in the background; daemonized APs log to /var/log/linux_post_install_hotspot.log.

Recipes:

• Give guests internet while tethered: pos network hotspot start wlan0 eth0 GuestNet secret.
• After starting, find who joined with pos network scan 192.168.42.0/24 (create_ap default subnet) or pos network checkport <phone-ip>:80.

Troubleshooting:

• create_ap not found → the precompiled binary wasn't installed; re-run ./install.sh (Phase 2 copies x64_bin/ → /usr/local/bin).
• "No suitable AP mode" → your Wi-Fi card/driver doesn't support AP mode; use the GUI (wihotspot-gui) or a USB dongle.
• Client has IP but no internet → check the <internet-iface> arg / NAT forwarding; create_ap --daemon logs to the hotspot logfile.

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pos network scan — find hosts on the LAN

Requires nmap (sudo apt install nmap).

pos network scan 192.168.1.0/24          # fast discovery
pos network scan 10.0.0.0/28 --full      # + OS, ports, services, NSE scripts
pos network scan 172.1.1.104             # single host
pos network scan 192.168.1.0/24 --retries 3

Two phases: fast ping-sweep discovery, then — only with --full — a detailed metadata scan on the alive hosts.

Recipe: after pos network hotspot start, find attached clients: pos network scan 192.168.42.0/24.

Troubleshooting: nmap missing → install it. Scanning a remote/hostile network without permission is not advisable; --full is slow — scope it to a /24 or a single host.

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pos network checkport — is a port open?

pos network checkport 192.168.1.1:80
pos network checkport 10.0.0.5:443

Exits non-zero if the port is closed/unreachable, so you can chain it:

Recipe: confirm a self-hosted service is up before alerting:

pos network checkport jellyfin.local:8096 && notify_send "Jellyfin reachable" \
  || notify_send "Jellyfin DOWN"

(see communication for notify_send).

Troubleshooting: a "closed" answer from a host that is up usually means a local firewall — check sudo pos system firewall rules and service binds (ss -tlnp).

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Related

• Reference tables: DOC/POS.md → network
• Firewall that may block these: system.md
• Public IP in the daily digest: system.md → health