Synolgy_docker_backup.sh

#!/bin/bash

location=<your backup location>
date=`date "+%Y%m%d"`

for name in $(docker ps --format '{{.Names}}'); do 
	#Backup location per container
	backup_location=$location"/"$name

	#Make the directory when it doesn't exist
	mkdir -p $backup_location
	
	#Find previous backup by its LATEST label
	previous_backup=`find $backup_location -name *LATEST*`
	if [ -z $previous_backup ]
	then
		#No backup made before, so just make one
		echo "No previous backup available. Lets make one and move along."
		docker inspect $name > $backup_location"/"$name".syno.LATEST.json"
	else
		#Determine if something changed in the configuration of the container
		
		#First make a new temp backup
		temp_backup=$backup_location"/"$name".syno.TEMP.json"
		docker inspect $name > $temp_backup
	
		#Load files
		prev_file=$(< $previous_backup)
		temp_file=$(< $temp_backup)

		if cmp -s "$prev_file" "$temp_file" ;
		then
			#No change, so we can keep the previous as LATEST
			rm $temp_backup
		else
			#Get last modification date of previous backup
			date_previous_backup=$(sudo stat --printf=%y $previous_backup | cut -c 1-10 -n)

			#Rename previous LATEST to last modification date
			new_previous_backup=$backup_location"/"$name".syno.v"$date_previous_backup".json"
			mv ${previous_backup} ${new_previous_backup}
			
			#Rename TEMP to LATEST
			latest_backup=$backup_location"/"$name".syno.LATEST.json"
			mv ${temp_backup} ${latest_backup}
		fi
	
	fi
done