Check if newer docker image available.

check_docker_newer_tag.sh

#!/bin/bash
# ensure running bash
if ! [ -n "$BASH_VERSION" ];then
    echo "this is not bash, calling self with bash....";
    SCRIPT=$(readlink -f "$0")
    /bin/bash $SCRIPT
    exit;
fi


REGISTRY="my.registry.com:5000"
REPOSITORY="awesome-project-of-awesomeness"


LATEST="`wget -qO- http://$REGISTRY/v1/repositories/$REPOSITORY/tags`"
LATEST=`echo $LATEST | sed "s/{//g" | sed "s/}//g" | sed "s/\"//g" | cut -d ' ' -f2`

RUNNING=`docker inspect "$REGISTRY/$REPOSITORY" | grep Id | sed "s/\"//g" | sed "s/,//g" |  tr -s ' ' | cut -d ' ' -f3`

if [ "$RUNNING" == "$LATEST" ];then
    echo "same, do nothing"
else
    echo "update!"
    echo "$RUNNING != $LATEST"
fi

Cronjob to check both image and source:

• auto update on source
• auto build on image
• auto recompose

#!/bin/sh
USER=<username on github>
REGISTRY=<username on docker hub>
UPSTREAM=<username on original source>
REPOSITORY=<the name of repository/project>
WORKDIR=/absolute/path/to/your/working/directory

eval `ssh-agent` && ssh-add -l
if grep -Fqe "Image is up to date" << EOF
`docker pull $REGISTRY/$REPOSITORY`
EOF
then
    cd $WORKDIR && rm -rf $REPOSITORY
    git clone git@github.com:$USER/$REPOSITORY.git
    cd $REPOSITORY && git checkout master
    git remote add upstream git://github.com/$UPSTREAM/$REPOSITORY.git
    git fetch --prune upstream
    if [ `git rev-list HEAD...upstream/master --count` -eq 0 ]
    then
        echo "both image and source are the same, do nothing"
    else
        echo "update exist on source, do update!"
        #Do update on source and get auto build image on docker hub
        git reset --hard upstream/master
        git push origin master --force
    fi
    cd $WORKDIR && rm -rf $REPOSITORY
else
    echo "newest image exist, do update!"
    #do recompose based on newest image
    docker-compose remove --volumes
    docker-compose up -d
fi
eval `ssh-agent -k`