second commit

README.md

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 # BallonSonde Project 2023
 This aim to group all ressources to create the PoC
 
+## Requirements
+   * GNU/Linux Debian 
+   * a RaspberryPi Zero 1.3 with nothing more (no WiFi, no BT)
+
+## Usages
+
+### chroot-to-pi.sh script
+Use this script to chroot your system on another system.

chroot-to-pi.sh

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+#!/bin/bash
+
+# This script allows you to chroot ("work on") 
+# the raspbian sd card as if it's the raspberry pi
+# on your Ubuntu desktop/laptop
+# just much faster and more convenient
+
+# credits: https://gist.github.com/jkullick/9b02c2061fbdf4a6c4e8a78f1312a689
+
+# make sure you have issued
+# (sudo) apt install qemu qemu-user-static binfmt-support
+
+# Write the raspbian image onto the sd card,
+# boot the pi with the card once 
+# so it expands the fs automatically
+# then plug back to your laptop/desktop
+# and chroot to it with this script.
+
+# Invoke:
+# (sudo) ./chroot-to-pi.sh /dev/sdb 
+# assuming /dev/sdb is your sd-card
+# if you don't know, when you plug the card in, type:
+# dmesg | tail -n30 
+
+
+# Note: If you have an image file instead of the sd card, 
+# you will need to issue 
+# (sudo) apt install kpartx
+# (sudo) kpartx -v -a 2017-11-29-raspbian-stretch-lite.img
+# then
+# (sudo) ./chroot-to-pi.sh /dev/mapper/loop0p
+# With the vanilla image, you have very little space to work on
+# I have not figured out a reliable way to resize it
+# Something like this should work, but it didn't in my experience
+# https://gist.github.com/htruong/0271d84ae81ee1d301293d126a5ad716
+# so it's better just to let the pi resize the partitions
+
+# check if package is not installed
+if [ $(dpkg-query -W -f='${Status}' qemu-user-static 2>/dev/null | grep -c "ok installed") -eq 0 ];
+
+mkdir -p /mnt/raspbian
+
+# mount partition
+mount -o rw ${1}2  /mnt/raspbian
+mount -o rw ${1}1 /mnt/raspbian/boot
+
+# mount binds
+mount --bind /dev /mnt/raspbian/dev/
+mount --bind /sys /mnt/raspbian/sys/
+mount --bind /proc /mnt/raspbian/proc/
+mount --bind /dev/pts /mnt/raspbian/dev/pts
+
+# ld.so.preload fix
+sed -i 's/^/#CHROOT /g' /mnt/raspbian/etc/ld.so.preload
+
+# copy qemu binary
+cp /usr/bin/qemu-arm-static /mnt/raspbian/usr/bin/
+
+echo "You will be transferred to the bash shell now."
+echo "Issue 'exit' when you are done."
+echo "Issue 'su pi' if you need to work as the user pi."
+
+# chroot to raspbian
+chroot /mnt/raspbian /bin/bash
+
+# ----------------------------
+# Clean up
+# revert ld.so.preload fix
+sed -i 's/^#CHROOT //g' /mnt/raspbian/etc/ld.so.preload
+
+# unmount everything
+umount /mnt/raspbian/{dev/pts,dev,sys,proc,boot,}