dockerimages_cron

#!/bin/bash

# (c) Harald Weidner, 2019-05-11
# License: MIT
#
# This is the cron job for Check_MK local check dockerimages.
#
# Put this file in /etc/cron.hourly and make it executable, or set
# up a separate cron job to run it regularly.
#
# Ths script stores the image repo digests of the current versions of all
# existing Docker container's images and stores them in the cache file.
#
# The script requires the tools skopeo and jq to be installed under /usr/bin.
#
# example output
# Format: Container name - Image name - Image ID - Digest on Registry
# adminer adminer sha256:0efd92e87a0eb4715c172bb6e08634bc7bdd6668916e9fc15a3517543fcfe014 sha256:37fda822ea8c2009b9d5f72672b539e16c39eb5ee87d5b9431436ea36dc5bb62
# portainer portainer/portainer sha256:19d07168491a3f9e2798a9bed96544e34d57ddc4757a4ac5bb199dea896c87fd sha256:d6cc2c20c0af38d8d557ab994c419c799a10fe825e4aa57fea2e2e507a13747d

CACHEDIR=/var/local/cache
CACHE=$CACHEDIR/dockerimages.cache
NEW=$CACHE.new

if [[ ! -x /usr/bin/skopeo ]]; then
  echo "dockerimg_cron requires the skopeo tool to be installed."
  exit 1
fi

if [[ ! -x /usr/bin/jq ]]; then
  echo "dockerimg_cron requires the jq tool to be installed."
  exit 1
fi

[[ -d $CACHEDIR ]] || mkdir -p $CACHEDIR

test -f $NEW && exit 0   # another instance is running
touch $NEW
 
for container in $(docker ps -a --format '{{.Names}}'); do
  read image_name image_id < <(docker inspect --format '{{.Config.Image}} {{.Image}}' $container)
  repodigest=$(/usr/bin/skopeo inspect docker://$image_name | jq -r .Digest)
  if [[ -n "$repodigest" ]]; then
    echo "$container $image_name $image_id $repodigest"
  fi
done >> $NEW

mv $NEW $CACHE

exit 0