Offline snapshot and import of container images using skopeo

backup_and_load_containers.sh

containers=(
  docker.io/library/consul:latest
  docker.io/library/vault:latest
  docker.io/library/redis:alpine
  docker.io/library/nginx:alpine
  docker.io/library/alpine:latest
)

urlencode() {
    # urlencode <string>
    old_lc_collate=$LC_COLLATE
    LC_COLLATE=C
    
    local length="${#1}"
    for (( i = 0; i < length; i++ )); do
        local c="${1:i:1}"
        case $c in
            [a-zA-Z0-9.~_-]) printf "$c" ;;
            *) printf '%%%02X' "'$c" ;;
        esac
    done
    
    LC_COLLATE=$old_lc_collate
}

urldecode() {
    # urldecode <string>

    local url_encoded="${1//+/ }"
    printf '%b' "${url_encoded//%/\\x}"
}

download_image_to_dir() {
    local outfile=$(urlencode ${1})
    local outdir="${2}"
    
    skopeo copy "docker://${1}" "oci-archive:${2}/${outfile}.tar"
}

download_all_containers() {
  local outdir="./containers"
  mkdir -p "${outdir}"
  
  for item in "${containers[@]}"
  do
    download_image_to_dir "${item}" containers/
  done
}

upload_image_to_storage() {
  local infile="${1}"
  local imgname="$(urldecode $(basename "${infile}" .tar))"

  skopeo copy "oci-archive:${infile}" "containers-storage:${imgname}"
    
}

upload_local_containers() {
  local indir="./containers"
  for item in $(find "${indir}" -maxdepth 1 -name '*.tar');
  do
    upload_image_to_storage "${item}"
  done
}