Bash script to backup all running MySQL docker instances via mysqldump

mysql_backup.sh

#!/bin/bash

#
# Script to backup all running mysql docker instances
#
# Usage:
#	Set the BACKUP_TARGET_DIR variable and call the script. Note that
#	the mysql containers must either have set the MYSQL_ROOT_PASSWORD environment variable
#	or the MYSQL_DATABASE MYSQL_USER MYSQL_PASSWORD environment variables.
#
# AUTHOR Robin Windey
# EMAIL ro.windey@gmail.com

BACKUP_TARGET_DIR="<HOST_PATH>"
MYSQL_VOLUME="/var/lib/mysql"

readarray -t running_containers_arr < <(docker ps --format='{{.ID}}')

for container in ${running_containers_arr[@]}; do
	docker inspect $container --format="{{.Config.Volumes}}" | grep "$MYSQL_VOLUME" -q
	# It's most likely a MYSQL container
	if [ $? -eq 0 ]; then
		container_name=$(docker inspect $container --format="{{.Name}}" | tr -d "/")
		readarray -t environment_arr < <(docker inspect $container --format="{{range .Config.Env}}{{println .}}{{end}}")

		root_pw=""
		db=""
		user=""
		pw=""

		for env_var in ${environment_arr[@]}; do
			(echo "$env_var" | grep -q "MYSQL_ROOT_PASSWORD") && root_pw=$(echo "$env_var" | sed -e 's/MYSQL_ROOT_PASSWORD=//g') && break
			(echo "$env_var" | grep -q "MYSQL_DATABASE") && db=$(echo "$env_var" | sed -e 's/MYSQL_DATABASE=//g') && continue
			(echo "$env_var" | grep -q "MYSQL_USER") && user=$(echo "$env_var" | sed -e 's/MYSQL_USER=//g') && continue
			(echo "$env_var" | grep -q "MYSQL_PASSWORD") && pw=$(echo "$env_var" | sed -e 's/MYSQL_PASSWORD=//g') && continue
		done

		echo "Run backup for ${container_name}"
		tmp_target="${MYSQL_VOLUME}/${container_name}.sql.gz"

		if [ ! -z "$root_pw" ]; then
			# if we have a root pw we use this to backup all databases in this instance
			docker exec $container bash -c "export MYSQL_PWD=$root_pw; /usr/bin/mysqldump -u root --all-databases | gzip -9 -c > $tmp_target"
		else
			# Otherwise we just backup one db
			docker exec $container bash -c "export MYSQL_PWD=$pw; /usr/bin/mysqldump -u $user --no-tablespaces $db | gzip -9 -c > $tmp_target"
		fi

		# Copy to host system
		docker cp $container:$tmp_target $BACKUP_TARGET_DIR
                docker exec $container rm -f $tmp_target
	fi
done