12 Deploy and Monitor
12 Deploy and Monitor
Calibration done; the script knows when to water. The last step is handing it off to cron so it runs on a schedule without you babysitting the terminal — and then optionally bringing it up under a small Flask web UI for at-a-glance monitoring from your phone. Cron is the source of truth for scheduling; the Flask UI is just a window onto the running system. Both are LAN-only; both are optional past the cron schedule. Most people stop after cron + SSH. That’s a complete, working build.
The cron schedule
Page 09’s setup-pi.sh already installed two cron entries — a 7am check and a 6pm check. Open the crontab with crontab -e to see them, or run crontab -l to print them without opening the editor. The two lines look like this:
0 7 * * * ~/irrigation/run.sh >> ~/irrigation/logs/cron.log 2>&1
0 18 * * * ~/irrigation/run.sh >> ~/irrigation/logs/cron.log 2>&1Each scheduled run executes ~/irrigation/run.sh (the venv-activator wrapper from page 09 that calls python3 irrigate.py), redirecting both stdout and stderr to the cron log at ~/irrigation/logs/cron.log. The script’s per-zone JSON log lives separately at ~/irrigation/logs/irrigation.json — that’s the structured one status.py reads.
What does 0 7 * * * mean? Cron’s five fields are minute, hour, day-of-month, month, day-of-week. 0 7 * * * reads as “minute 0, hour 7, every day, every month, every weekday” — 7am sharp every day. 0 18 * * * is the same thing at 6pm. The * means “any value.” If you want the full reference, man 5 crontab on the Pi has it.
Optional: midday check during Seattle’s dry season
In July and August, Seattle gets enough sun + heat that twice-a-day watering can fall behind. Add a third cron line for a midday check:
# Uncomment in July/August for a midday check
# 0 12 * * * ~/irrigation/run.sh >> ~/irrigation/logs/cron.log 2>&1To edit the crontab, run crontab -e from the Pi’s SSH session, paste the line in, save, and exit. Comment it back out in September when temperatures drop. The script is moisture-driven, not time-driven — adding a midday slot doesn’t water more often if soil is fine; it just gives the script another chance to notice if a zone went dry between 7am and 6pm.
The status script
status.py lives at ~/irrigation/status.py (page 09’s setup-pi.sh installed it alongside the irrigation script). Run it anytime you want a quick snapshot of what the system has been doing and what the sensors are reading right now:
cd ~/irrigation
source venv/bin/activate
python3 status.pyThe output prints two blocks. The first is recent activity — the last 10 entries from irrigation.json, each line showing timestamp, zone, action (watered or skip), moisture reading, and how many cycles ran. The second block is current sensor readings — a fresh ADC read per zone, averaged over 5 samples, with a DRY / OK / WET label based on the same thresholds the irrigation script uses. If a zone shows ERROR, the sensor isn’t responding (loose wire most likely; the Stuck? sidebar below points at the diagnostic).
Remote check from your laptop
You don’t have to SSH into the Pi and re-activate the venv every time you want a status check. Run the whole thing as a single SSH command from your laptop:
ssh [email protected] 'cd ~/irrigation && source venv/bin/activate && python3 status.py'That gives you the same two-block output, printed straight back to your laptop terminal. If irrigator.local doesn’t resolve (your phone or laptop doesn’t speak mDNS), fall back to the Pi’s IP address — page 09’s mDNS callout walks the lookup. macOS, modern Linux, and most home routers handle .local natively; older Windows machines sometimes don’t. If you’re on iOS/Android, an SSH client like Termux or Termius will resolve irrigator.local correctly when on the same WiFi.
Skip or stay? If “SSH from another device whenever I want a status check” is enough for you, you’re done with this page. The cron schedule keeps the irrigation running; status.py over SSH gives you visibility on demand. Novice readers: skip ahead to page 13 →. The Flask UI section below is for readers who want a phone-friendly status page on the LAN — it’s nicer, but not required for a complete build.
Optional: the Flask web UI
For at-a-glance status from any phone or tablet on your home WiFi, run a small Flask app on the Pi that exposes a status page at http://irrigator.local:8080/. It reads the moisture sensors + the log tail every page load and renders a single HTML page that meta-refreshes every 30 seconds. No JavaScript required. There’s a manual-water override behind a query-string key, but it’s LAN-only — never port-forward this to the public internet (the security caveat below covers why). The screenshots aren’t ready yet (Phase 7 ships the actual app); the ASCII mockups below show the layout the implementation is targeting.
The home page (GET /)
When you visit http://irrigator.local:8080/ from your phone, the home page shows current moisture per zone with a DRY / OK / WET label, the last few log entries, and the next scheduled cron run. In the shipped UI each zone is a coloured panel — DRY is pink, OK is green, WET is blue — so the status is legible at arm’s length without reading the label. The ASCII bars in the mockup below are an aspirational visual only; the actual rendering uses the coloured-panel treatment.
┌─────────────────────────────────────────────────────┐
│ Irrigator [auto-refresh] │
├─────────────────────────────────────────────────────┤
│ │
│ Zones │
│ ───── │
│ lettuce 14820 ████████░░░░ OK │
│ tomatoes 21340 █████████████ DRY │
│ raised_bed 11200 █████░░░░░░░ WET │
│ │
│ Recent activity │
│ ─────────────── │
│ 2026-04-26 18:00 tomatoes watered │
│ 2026-04-26 18:00 lettuce skip │
│ 2026-04-26 07:00 raised_bed watered │
│ 2026-04-26 07:00 tomatoes watered │
│ │
│ Next run: 2026-04-27 07:00 │
│ │
│ [Manual water form below — when ?key= is valid] │
└─────────────────────────────────────────────────────┘The page meta-refreshes every 30s — leave it open on a phone propped on the kitchen counter and you’ve got a live moisture display. No JS, no app to install; just a bookmark.
The manual-water override (POST /water)
When you arrive with a valid ?key= in the URL, the home page renders an inline form below the recent-activity log that lets you trigger a single zone for N seconds without waiting for the next cron run. Useful for “I just transplanted the lettuce and want to give it a drink right now” or “I’m bench-testing a new sensor and want to confirm the valve still fires.”
┌─────────────────────────────────────────────────────┐
│ Manual water │
├─────────────────────────────────────────────────────┤
│ │
│ Zone: [ tomatoes ▾ ] │
│ Seconds: [ 30 ] (1–120) │
│ │
│ [Run zone] │
└─────────────────────────────────────────────────────┘The form’s own action URL embeds the ?key= you arrived with — there’s no typed Key field on the form itself; the key travels as a query-string parameter on every submit. The form posts zone + seconds to /water?key=$IRRIGATOR_KEY. The Flask app validates the key, caps seconds at 120 (both client- and server-side — the form’s max attribute and a server-side check), and shells out to the existing manual_water.py to open the valve and run the pump for the requested duration. Without a valid key, the request is rejected with a 403; with one, the relevant zone fires immediately. Without ?key= in the URL the form simply doesn’t render — the home page shows a one-liner reminder to append the key to the URL. The 120s cap is the same safety limit manual_water.py already enforces from the command line — if you want longer, you’d have to edit the script and accept the risk of leaving a pump running.
Code listing + service unit
Phase 7 ships irrigator-web.py (the Flask app) and irrigator-web.service (a systemd unit that binds it to 0.0.0.0:8080 and restarts on failure). The service sources IRRIGATOR_KEY from /etc/default/irrigator-web so each install can have a unique key without baking it into source. The four existing scripts (irrigate.py, calibrate.py, status.py, manual_water.py) plus irrigator-web.py will all live at static/projects/balcony-irrigation/scripts/ for direct download — single-page checkout, no git clone needed.
Security caveat: LAN only. Do NOT port-forward port 8080 to the public internet. The shared ?key= is enough deterrent for casual nosy neighbors on your home WiFi; it is NOT enough to expose this anywhere a port-scanner can find it. The Flask app runs as a regular user with GPIO access, which means an attacker with the key can fire your pump on demand — annoying at worst on a balcony, catastrophic if the same pattern shows up on a system controlling a sprinkler valve indoors. If you want off-LAN access, see Tailscale below — never punch a hole in your router for this app.
Off-LAN access (advanced)
Tailscale is the right answer for off-LAN access without exposing port 8080 to the internet. Install Tailscale on the Pi (curl -fsSL https://tailscale.com/install.sh | sh, then sudo tailscale up), install Tailscale on your laptop or phone, and the Pi’s MagicDNS hostname (e.g., irrigator-pi.your-tailnet.ts.net) becomes reachable from anywhere you’ve authed Tailscale. http://irrigator-pi.your-tailnet.ts.net:8080/ works from any of those devices. WireGuard mesh-VPN under the hood; no port-forward, no public exposure, no NAT punch-through to debug.
Home Assistant integration via MQTT publishing is a v2 idea (REQUIREMENTS.md WEB-UI-V2-01); not in this build. The hook would be a small MQTT publish call from the irrigation loop that emits per-zone moisture + last-water-time so HA can plot it alongside the rest of your home sensors.
Build complete. Page 13’s diagnostic flowchart is your reference for when something stops working — bookmark it.