Bitfocus Companion cross-chroot for Raspberry Pi

guide.sh

## PART 1: get RPi image ready

# where the chroot will be
CHROOT=$(pwd)/chroot
# companion directory (will be bind-mounted to /companion)
COMPANION=$(pwd)/companion

# download latest Raspbian
wget https://downloads.raspberrypi.org/raspios_lite_armhf_latest -O raspbian.zip
unzip raspbian.zip          # decompress the image
IMAGE=$(pwd)/*raspios*.img  # find the inner image name (can be just replaced with absolute path to the image)

truncate -s +4G "$IMAGE"                        # make the image file larger
sudo losetup -f -P "$IMAGE"                     # bind it to a loop device
LOOPDEV=$(losetup -j "$IMAGE" | cut -d : -f 1)  # find out which loop device it is
echo "RPi image bound to $LOOPDEV"              # loopdev == /dev/loopN; can be just looked up in "losetup" output

# grow the main partition to full size
sudo parted "$LOOPDEV" resizepart 2 100% # or just resize this in "gparted /dev/loopN"
sudo e2fsck -f "${LOOPDEV}p2"  # check before filesystem resize
sudo resize2fs "${LOOPDEV}p2"  # resize filesystem

# make target directory
mkdir -p $CHROOT
# mount SD card filesystems
sudo mount "${LOOPDEV}p2" "$CHROOT"
sudo mount "${LOOPDEV}p1" "$CHROOT/boot"
sudo mkdir "$CHROOT/companion"
# bind-mount kernel filesystems
sudo mount --rbind /dev  "$CHROOT/dev"
sudo mount --rbind /sys  "$CHROOT/sys"
sudo mount --rbind /proc "$CHROOT/proc"
sudo mount --rbind /run  "$CHROOT/run"
sudo mount --bind "$COMPANION" "$CHROOT/companion"  # bind-mount companion folder
sudo mount --make-rslave "$CHROOT"  # magic sauce for umount -R (recursive unmounting)
# copy hostnames + dns config
sudo cp /etc/hosts /etc/resolv.conf /etc/hostname "$CHROOT/etc/"

# install qemu-user-static on host (QEMU needs to be 32bit: https://bugs.launchpad.net/qemu/+bug/1805913)
sudo apt install qemu-user-static:i386 binfmt-support
# copy QEMU to image (this is now our "interpreter" of ARM binaries on x86-64)
sudo cp /usr/bin/qemu-arm-static "$CHROOT/usr/bin/"

# and finally, enter the chroot
sudo -i chroot "$CHROOT"

## PART 2: installing software in the RPi image
# this happens inside the chroot

# update all the stuff
apt update
apt full-upgrade
# install required packages (libjepg-turbo may not be required though)
apt install npm cmake libusb-1.0-0-dev libudev-dev git libjpeg62-turbo-dev

# install node installer + yarn
npm install -g n
npm install -g yarn
# install latest node 8.x
n 8.17.0

## PART 3: compiling Companion
cd /companion     # fully cloned git repository expected in $COMPANION
./tools/yarn.sh   # compile everything
yarn run rpidist  # let's create a release zip (VERY SLOW! tries to compress the image very hard)
# alternatively transfer (or NFS/SMB/SSH/... mount) the whole directory to RPi and run it there with yarn; hopefully it works OK

## PART 4: cleaning up

exit  # leave chroot
sudo umount -R "$CHROOT"  # unmount all filesystems in the chroot directory
# NOTE: if the command above fails, try the --make-rslave trick again and then retry the unmounting:
  sudo mount --make-rslave "$CHROOT"
  sudo umount -R "$CHROOT"
sudo losetup -d "$LOOPDEV"  # free the loop device

## PART 5: reentering the chroot
IMAGE=$(pwd)/*raspios*.img                      # find the image
sudo losetup -f -P "$IMAGE"                     # bind it to a loop device
LOOPDEV=$(losetup -j "$IMAGE" | cut -d : -f 1)  # find out which loop device it is

# mount SD card filesystems
sudo mount "${LOOPDEV}p2" "$CHROOT"
sudo mount "${LOOPDEV}p1" "$CHROOT/boot"
# bind-mount kernel filesystems
sudo mount --rbind /dev  "$CHROOT/dev"
sudo mount --rbind /sys  "$CHROOT/sys"
sudo mount --rbind /proc "$CHROOT/proc"
sudo mount --rbind /run  "$CHROOT/run"
# bind-mount companion folder
sudo mount --bind "$COMPANION" "$CHROOT/companion"
sudo mount --make-rslave "$CHROOT" # magic sauce for umount -R (recursive unmounting)
# and now enter the chroot
sudo -i chroot "$CHROOT"