mrcharles
eb99b00a70
Solve the long-standing USB adapter enumeration shift problem: 9 Prolific
USB-to-DB9 adapters on pfv-tsys4 have no unique serial numbers and get
assigned /dev/ttyUSB0-8 based on enumeration order, which changes on every
reboot and breaks the old /root/conmap + manual screen workflow.
Solution: udev rules pin each adapter by its ID_PATH (physical USB port
topology), which is stable across reboots regardless of enumeration order.
Each adapter gets a named symlink in /dev/consoles/<name>. ser2net opens
these stable symlinks and exposes them on TCP ports (2001-2007) bound to
the Tailscale interface only. conman connects to those TCP ports for
session logging and multi-user console sharing.
Architecture (layered, no port sharing):
USB adapter → udev symlink → ser2net (TCP) → conman (logging + mux)
Port assignments (all on Tailscale IP 100.70.77.93):
2001 = pfv-core-sw01 2002 = pfv-tor3-mgmt 2003 = pfv-tor3-stor
2004 = pfv-rrinfra-rtr 2005 = pfv-r2-tor-top 2006 = subodev-torsw
2007 = pfv-r2-sw
Scripts (console/):
- mapping.txt: source of truth (TCP port | name | ID_PATH | baud | comment)
- generate-config.sh: generates udev rules, ser2net.yaml, conman.conf
entries from mapping.txt. Idempotent (markers in conman.conf for clean
regeneration). Uses | delimiter (ID_PATH values contain colons).
- setup.sh: full deploy — generate configs, create symlinks (udev trigger
+ manual fallback for already-discovered devices), create conmand
systemd unit (Debian doesn't ship one), restart services
- discover.sh: read-only USB adapter and service state discovery
- validate-conman.sh: verify conman→ser2net→device data path and log capture
Issues fixed during development:
- /dev/console is a kernel char device (major 5, minor 1) — cannot create
a directory there. Changed symlink namespace to /dev/consoles/.
- conman 0.3.x has no 'include' directive — CONSOLE entries written
directly into /etc/conman.conf between idempotent markers.
- Debian conman package has no systemd unit — created
/etc/systemd/system/conmand.service with After=ser2net ordering.
- conman.conf had no LOGDIR — logs weren't being written to
/var/log/conman/. Fixed by adding server logdir directive.
Validation: 7 symlinks resolving, 7 TCP ports on Tailscale, conmand with
7 consoles registered, 7 log files actively capturing console output,
both services enabled for reboot survival.
💘 Generated with Crush
Assisted-by: Crush:glm-5.2
110 lines
4.1 KiB
Markdown
110 lines
4.1 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 (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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bound to the **Tailscale interface only** (`100.70.77.93:200X`). conman
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connects to those TCP ports for session logging, output capture, and
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multi-user console sharing.
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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`).
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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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```bash
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# Via conman (with logging + multiplexing):
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conman -f pfv-core-sw01 # attach to console
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conman -q # query status of all consoles
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# Via telnet (direct, no logging):
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telnet 100.70.77.93 2001 # pfv-core-sw01
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# From any Tailscale-connected device:
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telnet pfv-tsys4 2001
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```
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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 (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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