Backup the Docker volumes of all running containers. This requires 'jq'. Currently it uses some Bashisms but can be easily changes for others shells I imagine.

dockervolbkp.sh

#!/bin/bash

BACKUPFOLDER="/opt/backups"
TIMESTAMP=$(date '+%Y-%m-%d')

if ! command -v jq &> /dev/null; then echo "Cannot find jq. Exiting ..."; exit 1; fi

# Get list of running containers
CONTAINERS=( $(docker ps --format '{{.Names}}') )

# Process each container
for CONTAINER in "${CONTAINERS[@]}"; do
    echo "Processing $CONTAINER"
    VOLUMES=( $(docker inspect $CONTAINER | jq '.[] | .Mounts | .[] | select(.Type == "volume") | .Name') )
    # explaining the jq script:
    #   .[] - take the given input as an array
    #   .Mounts - get the "Mounts" element
    #   .[] - the "Mounts" element is an array, so treat it thus and pipe out to the next step
    #   select(.Type == "volume") - select just the mounts that have a type of "volume"

    # Process each volume in the container
    for VOL in "${VOLUMES[@]}"; do
        # Strip out the " characters from the volume name
        VOL=${VOL//\"}
        echo "...Processing $VOL"

        # Run an alpine container that will be removed later. Into this I mount the volume and also a location to backup to.
        # I then run a tar command to backup the volume to this location.
        docker run --rm -v $VOL:/$VOL -v $BACKUPFOLDER:/backup alpine tar czf /backup/$TIMESTAMP-$CONTAINER-$VOL.tgz -C / $VOL
    done
done