modify_rpi_disk_image.sh

#!/bin/bash

# Usage:
# sudo ./modify_rpi_disk_image.sh raspbian-stretch-lite.img

function exit_with_error {
	echo "Error: $2"
	exit $1
}


function mount_raspbian_partitions {

	device="$1"
	boot_mount_location="$2"
	root_mount_location="$3"

	# Glob for any partitions
	partitions=("$device"p*)

	# Check if we got any partitions
	if [[ "${partitions[0]}" == "$device"p"*" ]]; then
		echo "Error: Could not find any partitions on device \"$device\"."
		return 1
	fi

	# Check that we have 2 partitions
	partition_count="${#partitions[@]}"
	if [[ "$partition_count" < "2" ]]; then
		echo "Error: Expected 2 partitions on device \"$device\" (device has $partition_count)"
		return 1
	fi

	# Seperate the two partitions
	img_loopback_boot="${partitions[0]}"
	img_loopback_root="${partitions[1]}"

	# Mount the boot partition
	mount "$img_loopback_boot" "$boot_mount_location"
	img_boot_mount_exit="$?"

	# Check for success
	[ "$img_boot_mount_exit" != "0" ] && return $img_boot_mount_exit

	# Mount the boot partition
	mount "$img_loopback_root" "$root_mount_location"
	img_boot_mount_exit="$?"

	# Check for success
	if [[ "$img_boot_mount_exit" != "0" ]]; then
		
		umount "$boot_mount_location"
		return $img_boot_mount_exit

	fi

	return 0

}


function mount_image_file {

	img_file_location="$1"
	boot_mount_location="$2"
	root_mount_location="$3"

	# Make sure it exists
	[ ! -e "$img_file_location" ] && exit_with_error 1 "Image file \"$img_file_location\" does not exist."

	# Set up the loop device
	img_loopback_device="$(losetup --show -f -P "$img_file_location")"
	img_losetup_exit="$?"

	# Bail if it wasn't successful
	if [[ "$img_losetup_exit" != "0" ]]; then
		
		echo "$Error mounting img file \"$img_file_location\":"
		echo "$img_loopback_device"

		# Pass on the error code
		return "$img_losetup_exit"

	fi

	# Mount the partitions
	mount_raspbian_partitions "$img_loopback_device" "$boot_mount_location" "$root_mount_location"
	img_mount_exit="$?"

	# Bail if it wasn't successful
	if [[ "$img_mount_exit" != "0" ]]; then
		
		# Undo the loopback mount
		losetup -d "$img_loopback_device"

		# Pass on the error code
		return "$img_mount_exit"

	fi

	echo "$img_loopback_device"

}


function convert_hex_to_background {

	background_hex="$1"

	dec_r=0
	dec_g=0
	dec_b=0

	if [[ ! -z "$background_hex" ]]; then

		hex_chars=$(echo "${background_hex^^}" | sed 's/#//g')

		hex_r=$(echo "$hex_chars" | cut -c-2)
		hex_g=$(echo "$hex_chars" | cut -c3-4)
		hex_b=$(echo "$hex_chars" | cut -c5-6)

		dec_r=$(echo "ibase=16;scale=2; $hex_r/FF" | bc | sed -r 's/^(-?)\./\10./')
		dec_g=$(echo "ibase=16;scale=2; $hex_g/FF" | bc | sed -r 's/^(-?)\./\10./')
		dec_b=$(echo "ibase=16;scale=2; $hex_b/FF" | bc | sed -r 's/^(-?)\./\10./')

	fi

	echo "$dec_r, $dec_g, $dec_b"
}


function write_plymouth_theme_file {
	
	themes_root="$1"
	theme_name="$2"
	theme_description="$3"

		cat <<EOF > "$themes_root/$theme_name/$theme_name.plymouth"
[Plymouth Theme]
Name=$theme_name
Description=$theme_description
ModuleName=script

[script]
ImageDir=/usr/share/plymouth/themes/$theme_name
ScriptFile=/usr/share/plymouth/themes/$theme_name/$theme_name.script
EOF

}


function write_plymouth_script_file {
	
	themes_root="$1"
	theme_name="$2"
	image_filename="$3"
	background_hex="$4"

	background="$(convert_hex_to_background "$background_hex")"

	cat <<EOF > "$themes_root/$theme_name/$theme_name.script"

# ========== Background Color ========== #

Window.SetBackgroundTopColor ($background);
Window.SetBackgroundBottomColor ($background);


# ============ Centered Logo =========== #

logo = Image("$image_filename");

logo_width = logo.GetWidth();
logo_height = logo.GetHeight();

screen_width = Window.GetWidth();
screen_height = Window.GetHeight();

scale = Math.Min( Math.Min( ( screen_width / 4 ) / logo_width, ( screen_height / 4 ) / logo_height ), 1);

logo_width = logo_width * scale;
logo_height = logo_height * scale;

logo = logo.Scale(logo_width, logo_height);

logo_sprite = Sprite( logo );
logo_sprite.SetPosition( ( screen_width - logo_width ) / 2, (screen_height - logo_height) / 2, -100);

EOF

}


function create_splashscreen_theme {

	filesystem_root="$1"
	theme_name="$2"
	theme_description="$3"
	image_path="$4"
	background_hex="$5"

	image_name="$(basename "$image_path")"
	themes_root="$filesystem_root/usr/share/plymouth/themes"

	# Make sure the theme directory exists
	mkdir -p "$themes_root/$theme_name"

	# Write the theme file
	write_plymouth_theme_file "$themes_root" "$theme_name" "$theme_description"

	# Write the theme file
	write_plymouth_script_file "$themes_root" "$theme_name" "$image_name" "$background_hex"

	# Copy the image
	cp "$image_path" "$themes_root/$theme_name/$image_name"
	chmod 644 "$themes_root/$theme_name/$image_name"

}


function append_or_uncomment {
	if grep -qG -- "^#$1$" "$2"; then
		sed -i "s/^#$1$/$1/g" "$2";
	else
		grep -qG -- "^$1$" "$2" || echo "$1" >> "$2"
	fi
}

function disable_overscan {

	filesystem_boot="$1"

	append_or_uncomment "disable_overscan=1" "$filesystem_boot/config.txt"

}

function enable_splashscreen_theme {

	filesystem_boot="$1"
	filesystem_root="$2"
	theme_name="$3"

	# Modify the boot command line 
	sed -i "s/console=tty1/console=tty3 splash quiet plymouth.ignore-serial-consoles logo.nologo vt.global_cursor_default=0/g" "$filesystem_boot/cmdline.txt"

	# Modify the boot config 
	append_or_uncomment "disable_splash=1" "$filesystem_boot/config.txt"

	# Write the Plymouth theme config
	cat <<EOF > "$filesystem_root/etc/plymouth/plymouthd.conf"
[Daemon]
Theme=$theme_name
EOF

}


function set_keyboard_language {

	filesystem_root="$1"
	language="$2"

	sed -i "s/XKBLAYOUT=.*/XKBLAYOUT=\"$language\"/g" "$filesystem_root/etc/default/keyboard"

}


function add_wifi_network {

	filesystem_root="$1"
	wifi_ssid="$2"
	wifi_password="$3"

	wpa_passphrase "$wifi_ssid" "$wifi_password" | grep -vF "#psk=" >> "$filesystem_root/etc/wpa_supplicant/wpa_supplicant.conf"

}

function run_as_pi {

	filesystem_root="$1"
	command="$2"
	
	proot -q qemu-arm -S "$filesystem_root" $command
}

function enable_auto_login {

	filesystem_root="$1"
	tty="$2"
	username="$3"

	run_as_pi "$filesystem_root" 'systemctl set-default multi-user.target'
	run_as_pi "$filesystem_root" "ln -fs /lib/systemd/system/[email protected] /etc/systemd/system/getty.target.wants/getty@$tty.service"
	cat > "$filesystem_root/etc/systemd/system/getty@$tty.service.d/autologin.conf" << EOF
[Service]
ExecStart=
ExecStart=-/sbin/agetty --skip-login --noclear --noissue --login-options "-f $username" %I \$TERM
EOF

}



img_file_location="$1"



# Make sure we were given an image file
[ -z "$img_file_location" ] && exit_with_error 1 "No image file specified."



# Make sure we have the right permissions
[ "$EUID" -ne "0" ] && exit_with_error 1 "This script must be run as root so it can mount the image and write in it's boot/root filesystems."



# Mount stuff
echo "Mounting image filesystems"

# Make some temp directories for our mounts
boot_mountpoint=$(mktemp -d)
root_mountpoint=$(mktemp -d)


# Mount the image file
img_loopback_device="$(mount_image_file "$img_file_location" "$boot_mountpoint" "$root_mountpoint")"
mount_image_file_exit="$?"
[ "$mount_image_file_exit" != "0" ] && exit_with_error "$mount_image_file_exit" "$img_loopback_device"


echo "Making modifications"


# Set the leyboard language
echo "Setting keyboard to \"us\""
set_keyboard_language "$root_mountpoint" "us"


# Create a new splashscreen theme
create_splashscreen_theme "$root_mountpoint" "kiosk-blue" "Custom Theme" "./icon-white.png" "#6666ff"


# Enable the theme
enable_splashscreen_theme "$boot_mountpoint" "$root_mountpoint" "kiosk-blue"


# Disable overscan
disable_overscan "$boot_mountpoint"


# Add Wifi
add_wifi_network "$root_mountpoint" "Test Wifi" "123456789"


# Install Xorg + Chromium
run_as_pi "$filesystem_root" "apt-get install -y --no-install-recommends xserver-xorg xserver-xorg-video-fbdev xinit pciutils xinput xfonts-100dpi xfonts-75dpi xfonts-scalable chromium-browser"


# Set hostname
echo "rpi-kiosk" > "$filesystem_root/etc/hostname"


# Disable sudo without password
rm "$filesystem_root/etc/sudoers.d/010_pi-nopasswd"


# Rename default user account
kiosk_user="kiosk"
run_as_pi "$filesystem_root" "usermod -l $kiosk_user pi"
run_as_pi "$filesystem_root" "usermod -m -d /home/$kiosk_user $kiosk_user"


# Setup auto-login
enable_auto_login "$filesystem_root" "tty1" "$kiosk_user"


# Quiet login
touch "$filesystem_root/home/$kiosk_user/.hushlogin"


# Setup xstart
echo "[[ -z \$DISPLAY && \$XDG_VTNR -eq 1 ]] && exec startx &> /dev/null" >> "$filesystem_root/home/$kiosk_user/.profile"

# Setup chrome auto-start
	cat > "$filesystem_root/home/$kiosk_user/.xinitrc" << EOF
xsetroot -solid "#6666ff"

while true; do
        /usr/bin/chromium-browser --app=https://google.com --window-position=0,0 --window-size=1921,1081
done
EOF

# Clean Up
echo "Cleaning up"

echo "Unmounting boot partition"
umount "$boot_mountpoint"
rm -r "$boot_mountpoint"

echo "Unmounting root partition"
umount "$root_mountpoint"
rm -r "$root_mountpoint"

echo "Removing loopback device"
losetup -d "$img_loopback_device"