Raspberry Pi attendance scheduler

Use an always-on Raspberry Pi to call the protected automatic-absence endpoint every five minutes while the application remains hosted on Vercel Hobby.

Configure the host

The Pi needs curl, systemd, working internet access, and synchronized system time. The application still performs all timezone and attendance calculations; the Pi holds no database credentials.

Create /etc/secure-qr-attendance/auto-absent.env as root:

APP_URL=https://your-production-domain.example
CRON_SECRET=the-same-secret-configured-in-vercel

Do not add quotes, trailing slashes, or spaces around =. Protect the file with mode 0600.

Copy the units from ops/systemd/ to /etc/systemd/system/, then enable them:

sudo install -d -m 0700 /etc/secure-qr-attendance
sudo install -m 0644 ops/systemd/secure-qr-auto-absent.service /etc/systemd/system/
sudo install -m 0644 ops/systemd/secure-qr-auto-absent.timer /etc/systemd/system/
sudo systemctl daemon-reload
sudo systemctl enable --now secure-qr-auto-absent.timer

Verify and operate

Run one sweep immediately and inspect its response and logs:

sudo systemctl start secure-qr-auto-absent.service
sudo systemctl status secure-qr-auto-absent.service
sudo journalctl -u secure-qr-auto-absent.service -n 20 --no-pager
systemctl list-timers secure-qr-auto-absent.timer

A successful call logs a JSON response with "status":"ok". A 401 means the Pi and Vercel CRON_SECRET values differ. Other HTTP failures are retried three times and remain visible in the system journal. The sweep is idempotent, so retrying or manually starting the service does not overwrite existing attendance records.