Check for Docker image updates

8 Feb 2019

Docker

For certain docker-driven services, I would like to check regularly for new versions. One way to do this is to query Docker Hub via Cronjob. Here I provide a little bash script to check for Docker image updates on Docker Hub.

#!/bin/bash
# Example usage:
# ./docker-image-update-check.sh gitlab/gitlab-ce update-gitlab.sh

IMAGE="$1"
COMMAND="$2"

echo "Fetching Docker Hub token..."
token=$(curl --silent "https://auth.docker.io/token?scope=repository:$IMAGE:pull&service=registry.docker.io" | jq -r '.token')

echo -n "Fetching remote digest... "
digest=$(curl --silent -H "Accept: application/vnd.docker.distribution.manifest.v2+json" \
    -H "Authorization: Bearer $token" \
    "https://registry.hub.docker.com/v2/$IMAGE/manifests/latest" | jq -r '.config.digest')
echo "$digest"

echo -n "Fetching local digest...  "
local_digest=$(docker images -q --no-trunc $IMAGE:latest)
echo "$local_digest"

if [ "$digest" != "$local_digest" ] ; then
    echo "Update available. Executing update command..."
    ($COMMAND)
else
    echo "Already up to date. Nothing to do."
fi

The script is also available as a GitHub Gist.

Here is a repository with this and some more scripts: https://gitlab.com/MatthiasLohr/omnibus-gitlab-management-scripts

If you have questions or problems, please create a ticket here.