[docker -CLI] Backup all images on the docker daemon to tag file, and those images had been pull from your private registry and using by the running containers.

save-img-to-tag.sh

#!/bin/bash

bkupdir="bkup_`date +%Y%m%d_%H%M%S`"
restorefile="$bkupdir/restore.sh"
log="$bkupdir/backup.log"

mkdir $bkupdir
echo "#!/bin/bash" > $restorefile
chmod u+x $restorefile

echo "backup folder: $bkupdir"
echo "backup folder: $bkupdir" >> $log

i=1

docker ps --format '{{.ID}} {{.Image}} {{.Names}} {{.Label "com.docker.swarm.service.name"}}' | \
grep << namespace of your private registry or other filter here ... >> | \
while read line
do
  ctrid=`echo $line | awk '{print $1}'`
  imgtag=`echo $line | awk '{print $2}'`
  ctrname=`echo $line | awk '{print $3}'`
  svcname=`echo $line | awk '{print $4}'`

  echo "$i. backup image for container $ctrname"

  echo "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~" >> $log
  echo -e "$i.\tbackup the image for container..." >> $log

  imgdigest=`docker container inspect --format "{{.Config.Image}}" $ctrid`
  imgid=`docker image inspect --format "{{.Id}}" $imgdigest`

  echo -e "\tcontainer id   : $ctrid" >> $log
  echo -e "\tcontainer name : $ctrname" >> $log
  echo -e "\tservice name   : $svcname" >> $log
  echo -e "\timage tag      : $imgtag" >> $log
  echo -e "\timage digest   : $imgdigest" >> $log
  echo -e "\timage id       : $imgid" >> $log
  echo -e "\t..." >> $log

  echo -e "\tdocker tag $imgid $imgtag" >> $log
  docker tag $imgid $imgtag

  if [ ! -f "$imgid.tar" ]; then
    echo -e "\tdocker image save --output $bkupdir/$imgid.tar $imgid" >> $log
    docker image save --output $bkupdir/$imgid.tar $imgid
    #touch $bkupdir/$imgid.tar
    echo "docker load --input $imgid.tar" >> $restorefile
  fi

  echo "docker tag $imgid $imgtag" >> $restorefile

  ((i=i+1))

done

echo "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~" >> $log
echo "End of backup log" >> $log