0-bootfiles

#!/bin/sh

#
# Script to deploy the boot files from rootfs to the boot partition
#
# This hook is meant to run in the `next` resinOS container
#

set -o errexit

# Variables
boot_fingerprint="@RESIN_BOOT_FINGERPRINT@"
bootfiles_blacklist="\
	/config.json \
	/config.txt \
	/extlinux/extlinux.conf \
	/splash/balena-logo.png \
	"
boot_mountpoint="/mnt/boot"
DURING_UDPATE=${DURING_UPDATE:-0}

# Checks if a file is present in the blacklist
# Arguments:
# 	$1: file to be checked
# Return value:
# 	0: file is blacklisted
# 	1: file is not blacklisted
isBlacklisted() {
	local _file="$1"
	for b in $bootfiles_blacklist; do
		if [ "$b" = "$_file" ]; then
			return 0
		fi
	done
	return 1
}

# Checks if a file was modified by verifying its fingerprint
# Arguments:
# 	$1: file to be checked
# Return value:
# 	0: file is modified
# 	1: file is not modified
isModified() {
	local _file="$1"
	local _current_md5
	_current_md5="$(md5sum "$boot_mountpoint/$_file" | awk '{print $1}')"
	local _initial_md5
	_initial_md5="$(grep "$_file" < "$boot_mountpoint/$boot_fingerprint" | awk '{print $1}')"
	if [ "$_current_md5" != "$_initial_md5" ]; then
		return 0
	else
		return 1
	fi
}

# Copies a file from /resin-boot to boot partition filesystem atomically and durable
# Arguments:
# 	$1: boot partition file
copyBootFile() {
	local _file="$1"
	mkdir -p "$boot_mountpoint/$(dirname "$_file")"
	if cp "/resin-boot/$_file" "$boot_mountpoint/$_file.new"; then
		sync -f $boot_mountpoint
		mv "$boot_mountpoint/$_file.new" "$boot_mountpoint/$_file"
		sync -f $boot_mountpoint
	else
		if [ "$DURING_UPDATE" = "1" ]; then
			# Cleanup all new files we deployed
			find "$boot_mountpoint" -type f -name "*.new" -exec rm -f {} \;
			for file in $new_deployed_files; do
				rm -f "$boot_mountpoint/$file"
			done
			exit 1
		fi
	fi
}

# Deploys files to boot partition
# Arguments:
# 	$1: file path relative to boot partition's root
deploy() {
	local _file="$1"
	printf "[INFO] Deploying %s%s..." "${boot_mountpoint}" "${_file}"
	if isBlacklisted "$_file"; then
		if [ "$_file" = "/splash/balena-logo.png" ]; then
			if [ -f "$boot_mountpoint/splash/resin-logo.png" ]; then
				if isModified "/splash/resin-logo.png"; then
					# Keep custom logo
					printf "renaming resin-logo to balena-logo..."
					sync -f $boot_mountpoint
					mv $boot_mountpoint/splash/resin-logo.png $boot_mountpoint/splash/balena-logo.png
					sync -f $boot_mountpoint
				else
					# This rebrands from old resin logo
					printf "replacing resin-logo with balena-logo..."
					copyBootFile "$_file"
					rm "$boot_mountpoint/splash/resin-logo.png"
				fi
				printf " done.\n"
				return
			fi
		fi
		printf "file blacklisted. Ignoring.\n"
	else
		if [ -f "$boot_mountpoint/$_file" ]; then
			if isModified "$_file"; then
				printf " overwriting modified file..."
				copyBootFile "$_file"
				printf " done.\n"
			else
				copyBootFile "$_file"
				printf " done.\n"
			fi
		else
			new_deployed_files="$new_deployed_files $_file"
			printf " new file..."
			copyBootFile "$_file"
			printf " done.\n"
		fi
	fi
}


#
# MAIN
#

# Do a dry run for copying the boot files and figure out if we would get in an
# out of space situation
boot_space="$(df -B1 --output=avail $boot_mountpoint | grep -v Avail)"
available="$boot_space"
available_threshold="524288" # All sizes in bytes
printf "[INFO] Checking if boot partition can accommodate the new update... "
for filepath in $(find /resin-boot -type f | sed 's#^/resin-boot##g'); do
	if isBlacklisted "$filepath"; then
		continue
	fi
	filesize=$(stat --format %s "/resin-boot${filepath}")
	available="$((available - filesize))"
	if [ "$available" -lt "$available_threshold" ]; then
		echo "fail."
		echo "[ERROR] Boot files copy operations will fail with out of space error."
		if [ "$DURING_UPDATE" = "1" ]; then
			exit 1
		fi
	fi
	if [ -f "${boot_mountpoint}${filepath}" ]; then
		available="$((available + $(stat --format %s "${boot_mountpoint}${filepath}")))"
	fi
done
echo "success."

# Deploy all files in the bootfiles list except fingerprint
new_deployed_files=""
for filepath in $(find /resin-boot -type f | sed 's#^/resin-boot##g'); do
	if [ "$filepath" != "/$boot_fingerprint" ]; then
		deploy "$filepath"
	fi
done
# Deploy fingerprint last
deploy "/$boot_fingerprint"