Install 32-bit docker on rpi (3, etc.)

update-docker-rpi.bash

#!/bin/bash

set -e

########################################
# 🧭 Configuration                     #
########################################
ARCH="$(dpkg --print-architecture)"
VERSION_CODENAME="$(grep -oP '(?<=\bVERSION_CODENAME=)[^;]+' /etc/os-release)"
URL="https://download.docker.com/linux/raspbian/dists/${VERSION_CODENAME}/pool/stable/${ARCH}/"
DOWNLOAD_DIR="${HOME}/.downloads/docker"
PATTERNS="^(containerd\.io|docker\-ce|docker\-ce\-cli|docker\-buildx\-plugin|docker\-compose\-plugin)_.*_${ARCH}\.deb$"

########################################
# 🧾 Functions                         #
########################################
print_help() {
  cat <<EOF
Usage: $0 [options]

Options:
  --dry-run     Show which files would be downloaded
  --no-log      Skip logging to a file
  --clean       Remove existing Docker packages before installing
  --quiet       Suppress non-essential output
  --debug       Enable debug messages
  --help        Show this help message and exit
EOF
}

parse_flags() {
  DRY_RUN=false
  NO_LOG=false
  CLEAN_FIRST=false
  QUIET=false
  DEBUG=false

  for arg in "$@"; do
    case "$arg" in
      --dry-run)    DRY_RUN=true ;;
      --no-log)     NO_LOG=true ;;
      --clean)      CLEAN_FIRST=true ;;
      --quiet)      QUIET=true ;;
      --debug)      DEBUG=true ;;
      --help)       print_help; exit 0 ;;
    esac
  done
}

log() {
  if ! $QUIET; then
    echo "$@"
  fi
}

log_debug() { if $DEBUG; then echo "🐞 DEBUG: $1"; fi }
log_info()  { log "ℹ️  $1"; }
log_warn()  { log "⚠️  $1"; }
log_error() { echo "❌ $1" >&2; }
log_success() { log "✅ $1"; }

run_test_stub() {
  log_info "Running test stub: $1"
  return 0
}

run_all_tests() {
  run_test_stub "parse_flags"
  run_test_stub "enable_logging"
  run_test_stub "clean_existing_docker"
  run_test_stub "prepare_download_dir"
  run_test_stub "fetch_file_list"
  run_test_stub "download_and_verify"
  run_test_stub "install_packages"
  run_test_stub "final_steps"
}

enable_logging() {
  if ! $NO_LOG; then
    mkdir -p "$DOWNLOAD_DIR"
    LOGFILE="${DOWNLOAD_DIR}/install.log"
    exec > >(tee -a "$LOGFILE") 2>&1
  fi
}

clean_existing_docker() {
  if $CLEAN_FIRST; then
    log "🧹 Cleaning existing Docker packages..."
    if $DRY_RUN; then
      log " DRY-RUN: apt cleaned of docker packages here ..."
    else
      sudo apt remove -y docker docker-engine docker.io containerd runc docker-ce docker-ce-cli docker-compose-plugin docker-buildx-plugin containerd.io || true
      sudo apt autoremove -y
    fi
  fi
}

prepare_download_dir() {
  mkdir -p "$DOWNLOAD_DIR"
  find "$DOWNLOAD_DIR" -type f -name '*.deb' -delete
  find "$DOWNLOAD_DIR" -type f -name '*.sha256' -delete
}

fetch_file_list() {
  log "📦 Fetching latest files from: $URL"
  log "📁 Download directory: $DOWNLOAD_DIR"

  mapfile -t DPKG_FILES < <(
    curl -s "$URL" | \
      grep -oP '(?<=href=")[^"]+' | \
      grep -v '/$' | \
      grep -E "$PATTERNS" | \
      sort | \
      awk -F'_' '
      {
          base = $1;
          files[base] = $0;
      }
      END {
          for (f in files) {
              print files[f]
          }
      }')

  if [[ ${#DPKG_FILES[@]} -eq 0 ]]; then
    log_warn "No matching files found."
    exit 0
  fi
}

download_and_verify() {
  for file in "${DPKG_FILES[@]}"; do
    if $DRY_RUN; then
      log "DRY-RUN:  $file downloaded here..."
    else
      log "⬇️  Downloading $file..."
      wget -q --show-progress --tries=3 --timeout=15 -O "${DOWNLOAD_DIR}/${file}" "${URL}${file}"

      SHA_FILE="${file}.sha256"
      log -n "🔍 Checking for checksum: $SHA_FILE... "
      if curl --silent --fail --head "${URL}${SHA_FILE}" > /dev/null; then
        log "found."
        curl -s "${URL}${SHA_FILE}" -o "${DOWNLOAD_DIR}/${SHA_FILE}"
        pushd "$DOWNLOAD_DIR" > /dev/null
        if ! sha256sum -c "$SHA_FILE"; then
          log_error "Checksum failed for $file!"
          exit 1
        fi
        popd > /dev/null
      else
        log "not found. Skipping validation."
      fi
    fi
  done
  log_success "All downloads complete."
}

install_packages() {
  log "🛠️  Installing..."
  pushd "$DOWNLOAD_DIR" > /dev/null
  if $DRY_RUN; then
    log "DRY-RUN:  dpkg -i ${DPKG_FILES[@]/#/./}"
  else
    if sudo dpkg -i "${DPKG_FILES[@]/#/./}"; then
      sudo rm -- "${DPKG_FILES[@]/#/./}"
    else
      log_error "dpkg install failed. Keeping downloaded files for inspection."
      exit 1
    fi
  fi
  popd > /dev/null
}

final_steps() {
  log_success "Installation complete."
  
  if ! $DRY_RUN; then
    sudo systemctl status docker

    if ! id -nG "$USER" | grep -qw docker; then
      log "🔧 Adding user '$USER' to docker group..."
      sudo groupadd -f docker
      sudo usermod -aG docker "$USER"
      log_warn "You must log out and log back in for group changes to take effect."
    else
      log_info "User '$USER' is already in the docker group."
    fi

    log "🚀 All done! Try: 'docker run hello-world' after logging back in."
  fi
}

report_summary() {
  log_success "Docker components downloaded and installed successfully:"
  for f in "${DPKG_FILES[@]}"; do
    log_success "  - $f"
  done
}

########################################
# 🚦 Main Execution                    #
########################################
parse_flags "$@"
run_all_tests
enable_logging
clean_existing_docker
prepare_download_dir
fetch_file_list
download_and_verify
install_packages
final_steps
report_summary

Assembled from various sources, I was looking for a convenient way to get 32-bit docker on a raspberry pi 3. With gpg key updates/expirations/depracations/etc., it's almost impossible to link "older" tech into the auto management system. So, here's a script that pulls the .deb files directly.