Automatically copy files when a new USB drive is plugged with udev

auto-copy.sh

#!/usr/bin/env bash

set -eu -o pipefail

NOCOLOR='\033[0m'
COLOR_ERROR='\033[1;31m' # bold red
COLOR_INFO='\033[1;36m' # bold cyan
COLOR_NOTE='\033[0;36m' # cyan

DESTINATION="/path/to/destination"
declare -a MOUNT_POINTS

_log ()
{
  local level="$1"
  local message="$2"
  local begin_color
  shift

  case "$level" in
    note)
      begin_color="$COLOR_NOTE"
      ;;
    info)
      begin_color="$COLOR_INFO"
      ;;
    error)
      begin_color="$COLOR_ERROR"
      ;;
    *)
      echo "Invalid level ${level}"
    ;;
  esac

  echo -e "${begin_color}[${level^^}] $message${NOCOLOR}"
}

_populate_mount_points ()
{
  local device="$1"
  local real_device mount_points

  real_device="$(systemd-escape -u -p "$device")"

  # Check that the device is a block device
  if [ ! -b "$real_device" ]; then
    _log error "Device $real_device does not exist!"
    exit 1
  fi

  mount_points="$(mount | grep -F "$real_device" \
    | sed -r -e 's/^.+ on (.+) type .*$/\1/g' || true)"
  if [ -z "$mount_points" ]; then
    _log error "No mount points found for $real_device."
    exit 1
  fi

  while IFS= read mount_point; do
    MOUNT_POINTS+=("$mount_point")
  done <<< "$mount_points"
}

_sanity_checks ()
{
  local destination="$1"

  if [ ${#MOUNT_POINTS[@]} -eq 0 ]; then
    _log error "No mount points given!"
    exit 1
  fi
  if [ ! -d "$destination" ]; then
    _log error "Directory $destination does not exist!"
    exit 1
  fi
}

_perform_copy ()
{
  local destination="$1"
  local base_source_basename source_basename new_dir i="1"

  for source in "${MOUNT_POINTS[@]}"; do
    base_source_basename="$(basename "$source")"
    source_basename="$(basename "$source")"

    while find "$destination" -mindepth 1 -maxdepth 1 \
        -name "$source_basename" | grep .; do
      source_basename="${base_source_basename}_$i"
      (( i += 1 ))
    done

    [ "$base_source_basename" != "$source_basename" ] \
      && _log note "Suffix added to ${base_source_basename} as it already existed."

    new_dir="${destination}/${source_basename}"

    _log info "Creating directory ${new_dir}"
    mkdir "${new_dir}"

    _log info "Copying from ${source} to ${new_dir}..."
    rsync -avP "${source}/" "${new_dir}"
    _log info "Finished copying from ${source} to ${new_dir}."
  done
}

main ()
{
  local device="$1"
  local destination="${2:-$DESTINATION}"

  _log info "Waiting 5 seconds for device to be mounted…"
  sleep 5

  _populate_mount_points "$device"

  _sanity_checks "$destination"

  _perform_copy "$destination"
}

main "$@"

auto-copy.sh

This script can be used in conjunction with a udev rule and a systemd user service to copy all the content from block device's partitions to a specified location. Following step can be followed to use it like so:

1. Copy the following udev rule in /etc/udev/rules.d/90-auto-copy.rules:

   ACTION=="add", KERNEL=="sd?", SUBSYSTEM=="block", ENV{ID_BUS}=="usb", \
     TAG+="systemd", PROGRAM="/bin/systemd-escape -p %N", \
     ENV{SYSTEMD_USER_WANTS}+="auto-copy@%c.service"
   

2. Create a systemd user service in $HOME/.config/systemd/user/auto-copy@.service. Get the name for the destination partition by running systemd-escape /path/to/mountpoint. Replace /path/to/auto-copy.sh with the proper path. Finally, either edit auto-copy.sh's _DESTINATION variable or pass it as the second argument in ExecStart= below:

   [Unit]
   Description=Copy files from new device to KINGSTON device
   Requires=run-media-user-KINGSTON.mount
   After=run-media-user-KINGSTON.mount
   
   [Service]
   ExecStart=/path/to/auto-copy.sh "%I"
   
   [Install]
   WantedBy=run-media-user-KINGSTON.mount
   

3. Activate the rule:

   udevadm control --reload && udevadm trigger

4. Follow logs for when new block device appear (a USB key, for example):

   journalctl --user -fu "auto-copy@*.service"