#!/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

# shellcheck source=/dev/null # Deactivate SC1090
# shellcheck disable=SC2015  # Deactivating bool hint
source "$(dirname "$(readlink -f "${0}")")/../base.sh" || (echo "Loading base.sh failed." && exit 1)

info "Making mount dir..." &&
mkdir -p /mnt/raspbian ||
error

info "Mount partitions..."
mount -o rw "$1""2"  /mnt/raspbian &&
mount -o rw "$1""1" /mnt/raspbian/boot ||
error

info "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 ||
error

info "ld.so.preload fix" &&
sed -i 's/^/#CHROOT /g' /mnt/raspbian/etc/ld.so.preload ||
error

info "copy qemu binary" &&
cp -v /usr/bin/qemu-arm-static /mnt/raspbian/usr/bin/ ||
error

info "You will be transferred to the bash shell now." &&
info "Issue 'exit' when you are done." &&
info "Issue 'su pi' if you need to work as the user pi." &&
info "chroot to raspbian" &&
chroot /mnt/raspbian /bin/bash ||
error

info "Clean up" &&
info "revert ld.so.preload fix" &&
sed -i 's/^#CHROOT //g' /mnt/raspbian/etc/ld.so.preload ||
error

info "unmount everything" &&
umount /mnt/raspbian/{dev/pts,dev,sys,proc,boot,} ||
error