Reboot Android devices automatically at a specific time (i.e. 3 AM) every day

Question

I have a rooted Lenovo Vibe K5 Plus (A6020a46) running TWRP + Arrow OS. It doesn't provide an automatically scheduled reboot out of the box. None of the apps worked. Also the apps that claim to provide this functionality are suspiciously ad-filled and I'm not comfortable giving root permission to them.

So, here is what I've tried till now:

• SMManager. Didn't work. Also, suspicious app.

• Wrote an infinite loop shell script, but I'm afraid it'll make my system too busy:

  while true; do
    if [[ "$(date +"%H")" -eq "3" ]] ; then
      reboot
    fi
  done
  

  But I don't know how to autorun it on boot and I'm afraid it'll break my Android

• Tried Termux (elevated) with cronie

  I'd put 0 3 * * * /system/bin/sh reboot in /data/crontab/root like mentioned in this link, but crond isn't recognised as a valid command in root shell.

Further, the init.d directory doesn't even exist, but an init directory does with a bunch of .rc files.

I've ran sudo crontab /data/crontab and then crontab -l lists the proper crontab, but it doesn't show up anywhere else. I'm not sure it will work. Further, I'll have to always manually run this (as far as I understand it) and seriously manually rebooting is infinitely easier.

I'm out of ideas. Any suggestions appreciated. I'd prefer shell scripts over shady apps.

Answer 1

Run the following shell script from init.d (or /data/adb/*.d/ in case of Magisk). Or run directly from init's .rc file. See How to run an executable on boot and keep it running?

#!/system/bin/sh -e

# ignore signals
for i in $(seq 64); do trap '' "$i"; done

# seconds until today 3AM
SECS=$(( $(date -d '03:00' +%s) - $(date +%s) ))

# if today's 3AM has passed, set it to tomorrow's
[ SECS -gt 0 ] || SECS=$((SECS + 86400))

# wait until 3AM
echo "${0##*/}: sleeping for $SECS seconds"
sleep $SECS

# Reboot device
echo "${0##*/}: restarting"
/system/bin/reboot scheduled-reboot ||
/system/bin/setprop sys.powerctl reboot,scheduled-reboot