Docker - check private registry image version

Brownie points to @mbarthelemy and @amuino who put me on track. From that I was able to come up with the following bash script that others may find useful. It just checks if the tag on the registry is different from the currently executing container.

#!/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

Not sure about the version but if you mean the tag of image, it can be easily checked through the registry v2 api . Note that in context of docker images tag has nothing to do with the version of software.

Use curl command in CLI

 curl <docker_host_ip>:<docker_host_port>/v2/<repository_name>/tags/list

To get a list of repositories pushed on the private registry, use

curl <docker_host_ip>:<docker_host_port>/v2/_catalog

Even when there is no command, you can use the API to check for tags on the registry and compare against what you are running.

$ curl --silent my.domain.com:5000/v1/repositories//project1/tags | grep latest
{"latest": "116f283e4f19716a07bbf48a562588d58ec107fe6e9af979a5b1ceac299c4370"}

$ docker images --no-trunc my.domain.com:5000/project1
REPOSITORY           TAG                 IMAGE ID                                                           CREATED             VIRTUAL SIZE
my.domain.com:5000   latest              64d935ffade6ed1cca3de1b484549d4d278a5ca62b31165e36e72c3e6ab8a30f   4 days ago          583.2 MB

By comparing the ids, you can know that you are not running the latest version.