ApplPi OS v0.4.0

Images for older Raspberry Pis (32-bit, armhf; tested on a Pi 2). Write one with applpi flash v0.4.0, or update a Pi with applpi update <pi> v0.4.0. Both download the image and check it against SHA256SUMS.

What's new

• Apps can ask the OS for a few things through app-request, and nothing else:
  • install a new version of themselves, on trial: if the new version doesn't stay up for 30 seconds, the old one comes back;
  • set the time zone and time server;
  • restart the Pi.
• Each app has its own watchdog. If an app turns it on and then stops responding, it is restarted.
• rpi_ws281x is in the image for LED apps. An app that uses the PWM hardware sets "pwm": true in app.json, and the onboard audio is left off for it.
• Images are published: applpi flash and applpi update accept a release name or latest.

Tested

• In QEMU: two boots and an update to the other slot.
• On a Pi 2 with an app, including an OS update that broke the app, which went back to the old slot.