Pulls a Docker image and compares it to running ones. Stops/removes/restarts the ones that are outdated. Warning: This is obviously a few years old and has not been updated. Do not use unless you review and ensure it's still OK. BTW, there are better ways to do this today.

update_docker

#!/usr/bin/env bash
# Pulls a Docker image and compares it to running ones. Stops/removes/restarts the ones that are outdated.
# Put in /etc/cron.daily and make executable. One per image.
# From: http://stackoverflow.com/questions/26423515/how-to-automatically-update-your-docker-containers-if-base-images-are-updated/26548914

set -e
IMAGE="<DEVELOPER>/<DOCKERIMAGE>:latest"
CID=$(docker ps | grep $IMAGE | awk '{print $1}')
docker pull $IMAGE

for im in $CID
do
    LATEST=`docker inspect --format "{{.Id}}" $IMAGE`
    RUNNING=`docker inspect --format "{{.Image}}" $im`
    NAME=`docker inspect --format '{{.Name}}' $im | sed "s/\///g"`
    echo "Latest:" $LATEST
    echo "Running:" $RUNNING
    if [ "$RUNNING" != "$LATEST" ];then
        echo "upgrading $NAME"
        docker stop $NAME
        docker rm -f $NAME
        docker run <WHATEVER RUN CONFIGURATION YOU ARE NORMALLY USING>
    else
        echo "$NAME up to date"
    fi
done