KindleCron - cron-like task scheduling that survives deep sleep

[lennardollesch]

KindleCron (kcron)

KindleCron runs scheduled jobs on a jailbroken Kindle reliably and to the second,
while letting the device sleep between them. It is a single static binary with no
dependencies.


Features

• Full cron expressions (5- or 6-field, optional seconds), plus one-shot once schedule
• Survives suspend via powerd's rtcWakeup; no need to keep the device awake
• Optional keep-awake for sub-minute jobs, with a battery warning
• Per-job timeout; a hung job is killed and can never pin the device awake
• Catches up on runs missed while the device was off
• Optional KUAL menu

Tested on
Kindle Basic 10th gen (KT4, FW 5.13.6) and Paperwhite 4 (PW4, FW 5.17.1.0.3). Other
jailbroken models with the same powerd service should work - reports welcome.

Requirements
A jailbroken Kindle. KUAL is optional (you can run the binary directly).

Install
Download the latest release, unzip, connect over USB, and copy the extensions
and kcron folders to the root of the Kindle drive.


Source & releases

GitHub: https://github.com/lennardollesch/KindleCron

The RTC-wakeup approach is based on yparitcher's thread and the powerd
documentation comes from the KindleModding project - thanks to both.
Feedback and reports of additional working models are welcome.

[lennardollesch]

KindleCron v0.2.0 - the binary is now called kron

A new release is up: https://github.com/lennardollesch/Ki...eleases/latest

Thanks to skylarplayz348 for the suggestion behind the rename.

Please note this is not a drop-in replacement. The command, its folder and the
KUAL extension are now called kron instead of kcron. Upgrade steps are at the
bottom of the release notes; existing jobs carry over if you move the jobs.d and
state folders across.

What is new

• kron setup symlinks the binary into /usr/bin, so you can type kron from any shell and any other program can call it too. It survives reboots, it finds itself wherever you put the binary, and it deals with the read-only rootfs for you. kron unlink reverses it. There is a Setup entry in KUAL.
• New -eips flag prints a command's result onto the screen. This is what makes the KUAL menu usable: previously an action either worked or silently did nothing, now you get a readout for Start, Stop, Setup, purge, kill-jobs and so on. The menu was reorganised, with confirmations on the destructive entries.
• Defined exit codes (0 ok, 2 invalid request, 1 other failure), so you can drive kron from a script and check the result instead of parsing its output.
• A batch of robustness fixes: logging no longer breaks when KUAL closes stdout, stop no longer trusts a stale lock file from a crashed daemon, job names are validated, and state files are flushed to storage before they are swapped in, so a flat battery cannot corrupt them.
• clean-logs is now clear-logs, and $KCRON_DIR is now $KRON_DIR.

Still the same single static binary, still no dependencies on the device, still
sleeping between jobs via the RTC wake-up during readyToSuspend.

Feedback and reports of additional working models are welcome as always.