61 lines
2.4 KiB
Markdown
61 lines
2.4 KiB
Markdown
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# 03 — SSH, mDNS and Tailscale on Termux
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Termux's Bionic libc does **not** resolve `.local` names. This repo ships small Python helpers that fix this without needing root or a custom resolver.
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## Scripts involved
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| Script | Role |
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|--------|------|
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| `mdns-resolve` | Resolve `<host>.local` via raw multicast UDP. Returns the IP or non-zero. |
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| `mdns-publish.py` | Publish this device on the LAN as `movil.local` (or whatever you choose) using `zeroconf`. |
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| `ssh-mdns-proxy` | SSH `ProxyCommand` that tries mDNS first, then Tailscale DNS. Used from `~/.ssh/config`. |
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| `ssh-fallback` | Lower-level fallback: tries Tailscale, then LAN. Useful when Tailscale is flaky. |
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## SSH config
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Drop the contents of `config/ssh_config.example` into `~/.ssh/config` (or merge it).
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The key entries:
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```ssh-config
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Host *.local
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ProxyCommand ~/.local/bin/ssh-mdns-proxy %h %p
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Host lenovo-ideapad
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ProxyCommand ~/.local/bin/ssh-mdns-proxy %h %p
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Host *.YOUR-TAILNET.ts.net
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User YOUR_USER
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```
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Adjust the username and the tailnet domain. The proxy command will try mDNS first, then fall through to your Tailscale magic-DNS name (env `TAILSCALE_DOMAIN`).
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## Publishing this device as `movil.local`
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If you want the device to be reachable as `movil.local` from your LAN:
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```bash
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# One-shot foreground (to see errors):
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python ~/.local/bin/mdns-publish.py
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# Background (typical use, from ~/.bashrc):
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nohup python ~/.local/bin/mdns-publish.py >>~/.cache/mdns.log 2>&1 &
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disown
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```
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**Gotcha:** `zeroconf` (the pip package) is **not** part of a `pkg`-managed install. If you restore Termux from a `tar` backup, `zeroconf` will be missing from `$PREFIX/lib/python*/site-packages` and the script will silently fail with `ModuleNotFoundError`. Re-run `pip install zeroconf` after every restore.
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## Logging, not silencing
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The `.bashrc` auto-start lines in this repo (`config/bashrc.snippet`) deliberately log to a file instead of `/dev/null`. Silent failures are the single most painful class of bug after a restore — keep the logs.
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## Tailscale
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Tailscale on Termux runs **as the Android app**, not as a CLI inside Termux. You can't `tailscale up` from a shell. The app provides magic DNS for `*.YOUR-TAILNET.ts.net`, which Bionic-libc resolves fine (it's just a regular DNS query).
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When you list hosts in `~/.ssh/config`, prefer:
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1. `<host>.local` for fast LAN access
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2. `<host>.YOUR-TAILNET.ts.net` for off-LAN
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Never hardcode IPs — they rotate.
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