131 lines
5.1 KiB
Markdown
131 lines
5.1 KiB
Markdown
# Console Management (ser2net + conman)
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Network-accessible serial console management for all production network
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switches and routers, running on **pfv-tsys4** (storage server).
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## Architecture
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```
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USB-DB9 adapters → udev symlinks (/dev/consoles/<name>) → ser2net telnet(rfc2217) TCP → conman (logging + multiplexing)
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```
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ser2net owns the physical serial devices and exposes them on TCP ports
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using the **telnet(rfc2217) protocol** bound to the **Tailscale interface
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only** (`100.70.77.93:200X`). conman connects to those TCP ports via
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telnet for session logging, output capture, and multi-user console
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sharing.
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**Why telnet(rfc2217)?** The serial devices send `
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` (LF+CR) line
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endings instead of standard `
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`. Raw TCP transport caused conman's
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telnet NVT to strip bare CR characters, producing stair-stepped output.
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With telnet(rfc2217) on both sides, binary mode is negotiated and CR/LF
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translation is handled correctly by the telnet layer.
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**conman and ser2net do NOT share ports** — only one process can open a
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serial device at a time. ser2net owns the physical device; conman connects
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over TCP.
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## The USB Enumeration Problem (SOLVED)
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The 9 Prolific USB-to-DB9 adapters (`067b:2303`) on pfv-tsys4 have **no
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unique USB serial numbers** and get assigned `/dev/ttyUSB0-8` based on
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enumeration order, which shifts on every boot. This made the old
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`/root/conmap` + manual `screen` workflow break after every reboot.
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**Fix:** udev rules pin each adapter by its **ID_PATH** (physical USB port
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topology), which is stable across reboots regardless of enumeration order.
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Each adapter gets a named symlink in `/dev/consoles/` that never changes.
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The udev rules are generated from `mapping.txt`, which maps each adapter's
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ID_PATH to a console name and TCP port. To re-map after physically moving
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an adapter, update `mapping.txt` and re-run `setup.sh`.
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**Fallback:** if udev trigger doesn't create symlinks for already-discovered
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devices (common on first run), `setup.sh` creates them manually by matching
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ID_PATH. On subsequent boots, udev creates them automatically.
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## Port Assignments
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| TCP Port | Console Name | ID_PATH | Description |
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|----------|-------------|---------|-------------|
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| 2001 | pfv-core-sw01 | usb-0:1.5.4.4 | Dell PowerConnect 5448 (core switch) |
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| 2002 | pfv-tor3-mgmt | usb-0:1.6.3.1 | Rack 3 management TOR switch |
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| 2003 | pfv-tor3-stor | usb-0:1.6.3.3.2 | Rack 3 storage TOR switch |
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| 2004 | pfv-rrinfra-rtr | usb-0:1.6.3.3.1 | Cisco router (rrinfra) |
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| 2005 | pfv-r2-tor-top | usb-0:1.6.3.3.3 | Rack 2 top-of-rack switch |
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| 2006 | subodev-torsw | usb-0:1.5.4.1 | Suborbital device TOR switch |
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| 2007 | pfv-r2-sw | usb-0:1.6.3.2 | Rack 2 old Dell switch |
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All ports listen on the Tailscale IP (`100.70.77.93`) using telnet(rfc2217).
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## Scripts
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| Script | Purpose |
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|--------|---------|
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| [`mapping.txt`](mapping.txt) | Source of truth: TCP port ↔ ID_PATH ↔ name ↔ baud |
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| [`generate-config.sh`](generate-config.sh) | Generates udev rules, ser2net.yaml, conman.conf from mapping.txt |
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| [`setup.sh`](setup.sh) | Full deploy: generate configs, create symlinks, restart services |
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| [`discover.sh`](discover.sh) | Read-only discovery of USB adapters, existing config, services |
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## Usage
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### Connect to a console
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**Primary method — conman client (with logging + multiplexing):**
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```bash
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# From any Tailscale-connected workstation:
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conman -d pfv-tsys4:7890 -f pfv-core-sw01 # connect to console
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conman -d pfv-tsys4:7890 -q # list all consoles
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```
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Escape sequence: `&.` to disconnect, `&?` for help.
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**Direct telnet (emergency only — conflicts with conman):**
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```bash
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# Direct telnet to ser2net works ONLY when conmand is stopped, because
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# conmand maintains persistent connections to all 7 TCP ports. Use:
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ssh pfv-tsys4 'systemctl stop conmand'
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telnet pfv-tsys4 2001 # pfv-core-sw01
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ssh pfv-tsys4 'systemctl start conmand' # restart when done
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```
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**Do NOT use telnet while conmand is running** — conmand will reconnect
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and kick your telnet session immediately ("Connection closed by foreign host").
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The correct workflow is conman client → conmand → ser2net → device.
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### Re-deploy after changing mapping.txt
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```bash
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PROX_HOST=pfv-tsys4 bash tests/remote.sh prox 'bash /root/console/setup.sh'
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```
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### Find the ID_PATH for a new adapter
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```bash
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PROX_HOST=pfv-tsys4 bash tests/remote.sh prox-file console/discover.sh
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```
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Then match the new adapter's ID_PATH to its physical location and add a line
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to `mapping.txt`.
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## Files on pfv-tsys4
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| File | Purpose |
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|------|---------|
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| `/etc/udev/rules.d/99-console-ports.rules` | Stable symlinks by ID_PATH |
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| `/etc/ser2net.yaml` | ser2net config (telnet rfc2217 TCP ports → serial symlinks) |
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| `/etc/conman.conf` | conman config (CONSOLE entries between markers) |
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| `/etc/systemd/system/conmand.service` | systemd unit for conmand |
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| `/root/console/mapping.txt` | Copy of the source-of-truth mapping |
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| `/root/console/setup.sh` | Setup script (re-runnable) |
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| `/root/console/generate-config.sh` | Config generator |
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## Old workflow (replaced)
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The old `/root/conmap` file and manual `screen` sessions are no longer
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needed. The new setup is fully automated and survives reboots.
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