docker orphaned overlay2 cleanup script

docker-overlay-prune.sh

#!/bin/bash
# partly based on https://stackoverflow.com/a/72548686

[[ $(id -u) -eq 0 ]] || exec sudo /bin/bash -c "$(printf '%q ' "$BASH_SOURCE" "$@")"
progname=$(basename $0)
quiet=false
no_dry_run=false
while getopts ":qn" opt; do
  case "$opt" in
    q)
      quiet=true
      ;;
    n)
      no_dry_run=true
      ;;
    ?)
      echo "unexpected option ${opt}"
      echo "usage: ${progname} [-q|--quiet]"
      echo "    -q: no output"
      echo "    -n: no dry run (will remove unused directories)"
      exit 1
      ;;
  esac
done
shift "$(($OPTIND -1))"

[[ ${quiet} = false ]] || exec /bin/bash -c "$(printf '%q ' "$BASH_SOURCE" "$@")" > /dev/null

images=( $(docker image ls --all --format "{{.ID}}") )
mounted=$(mount | grep "/var/lib/docker/overlay2/")
dirs=( $(find /var/lib/docker/overlay2 -mindepth 1 -maxdepth 1 -type d -not -path ./l -exec basename {} \;) )
unused=()
echo "Scanning for used overlays2 dirs."
for d in "${dirs[@]}"; do
  used=0
  dname=${d//"-init"/}

  # check for mounted overlays
  echo ${mounted} | grep -q ${dname}
  if [[ $? = 0 ]]; then
    continue
  fi

  # check for overlays being used by images
  for id in ${images[@]}; do
    docker inspect $id | grep -q $dname
    if [[ $? = 0 ]]; then
      used=1
      break
    fi
  done

  # if not used add to unused array
  if [[ ${used} -eq 0 ]]; then
    unused+=("${d}")
  fi
done

if [ ${#unused[@]} -gt 0 ]; then
  [[ ${no_dry_run} = true ]] || echo "Could remove:  (to automatically remove, use the -n, "'"'"no-dry-run"'"'" flag)"
  for d in "${unused[@]}"; do
    if [[ ${no_dry_run} = true ]]; then
      echo "Removing /var/lib/docker/overlay2/${d}"
      rm -rf /var/lib/docker/overlay2/${d}
    else
      echo " /var/lib/docker/overlay2/${d}"
    fi
  done
  echo Done
else
  echo "All overlay2 directories are used, nothing to clean up."
fi