Run script once unattended once when system has booted

Question

I am currently creating a very minimal image for the Raspberry Pi 4. And I need the image itself to be as small as possible in order to reduce the time to flash the SD-card.

I do however, want to expand the file-system automatically when the Raspberry Pi 4 first boot.

I just threw this into a bash-script:

#!/bin/bash -x -e
raspi-config nonint do_expand_rootfs
rm -- "$0"
reboot

Running this works, but how to I run this just once when the Pi boots?

Answer 1

Yes, there is a quite simple way to do this!

First, place your expand-script in a good folder, like /usr/local/bin/expand.sh, and make it executable with chmod +x /usr/local/bin/expand.sh

Then, edit /boot/config.txt and add the following furthest down:

[expansion]
init=/usr/local/bin/expand.sh

Reboot, and then observe the expanded filesystem with df -h