A bash script to very easily create a bootable USB device from one ISO file. Just curl it, chmod it and go!

bootiso

#!/bin/bash

# Author: jules randolph <jules.sam.randolph@gmail.com> https://github.com/jsamr
# License: MIT
#
# Usage: [<options>] <file.iso>
#
# Create a bootable FAT32 USB device from a linux-GNU/unix ISO.
#
# Options
#  -n, --no-bootloader          Do not add syslinux bootloader.
#  -d, --device  <device>       Select <device> as USB device.
#                               Device should be in the form /dev/sXX or /dev/hXX.
#                               You will be prompted to select a device if you don't use this option.
#  -f, --force-iso              Disable mime-type check on ISO file.
#
# How it works
#
# The script walks through the following steps:
# 0. Check dependencies and prompt user to install any missing.
# 1. Check provided ISO exists and has the expected application/x-iso9660-image mime-type.
# 2. If given with -d option, check that the selected device exists and is not a partition. Otherwise, prompt the user to select a device.
# 3. Prompt the user for confirmation that data might be lost for selected device if he goes to next step.
# 4. Unmount the USB if mounted, blank it and delete existing partitions.
# 5. Create a FAT32 partition on the USB device.
# 6. Create a temporary dir to mount the ISO file and mount it.
# 7. Create a temporary dir to mount the USB device and mount it.
# 8. Copy files from ISO to USB device.
# 9. If option --no-bootloader is not selected, install a bootloader with syslinux in slow mode.
# 10. Unmount devices and remove temporary folders.

dependencies=('lsblk' 'grep' 'file' 'sfdisk' 'mkfs.vfat' 'syslinux' 'mtools' 'rsync')
scriptName=$(basename "$0")

selectedDrive=''
selectedPartition=''
selectedIsoFile=''
isoMountPoint=''
usbMountPoint=''

# options

addSyslinuxBootloader=true
disableMimeCheck=false

help_message="\
Usage: $scriptName [<options>] <file.iso>
Create a bootable FAT32 USB from a linux-GNU/unix ISO.

Options
  -n, --no-bootloader          Do not add syslinux bootloader.
  -d, --device  <device>       Select <device> as USB device.
                               Device should be in the form /dev/sXX or /dev/hXX.
                               You will be prompted to select a device if you don't use this option.
  -f, --force-iso              Disable mime-type check on iso file.
"

display_help() {
  echo "$help_message"
}

echoerr() {
  >&2 echo -e "\\033[0;31m$1\\033[0m"
}

echowarn() {
  echo -e "\\033[1;33m$1\\033[0m"
}

failAndExit() {
  echoerr "$1\\nExiting $scriptName..."
  exit 1
}

initPckgManager() {
  if [ ! -z "$(which apt-get)" ]; then # Debian
    pkgmgr="apt-get -y install"
    return 0
  fi
  if [ ! -z "$(which yum)" ]; then # Fedora
    pkgmgr="yum -y install"
    return 0
  fi
  if [ ! -z "$(which dnf)" ]; then # Fedora
    pkgmgr="dnf -y install"
    return 0
  fi
  if [ ! -z "$(which pacman)" ]; then # Arch
    pkgmgr="pacman -S"
    return 0
  fi
  if [ ! -z "$(which zypper)" ]; then # OpenSuse
    pkgmgr="zypper install"
    return 0
  fi
  if [ ! -z "$(which emerge)" ]; then # Gentoo
    pkgmgr="emerge"
    return 0
  fi
}

init() {
  if ((EUID != 0)); then
    if [[ -t 1 ]]; then
      sudo "$0" "$@"
    else
      exec 1>output_file
      gksu "$0" "$@"
    fi
    exit
  fi
  initPckgManager
}

parseOptions() {
  typeset key
  while [[ $# -gt 0 ]]; do
  key="$1"
  case $key in
      -n|--no-bootloader)
      addSyslinuxBootloader=false
      shift
      ;;
      -d|--device)
      selectedDrive="$2"
      shift
      shift
      ;;
      -f|--force-iso)
      disableMimeCheck=true
      shift
      ;;
      -*)
        if [ ! -f "$key" ]; then
          failAndExit "Unknown option \`$key'."
        fi
        selectedIsoFile=$1
      ;;
      *)
      selectedIsoFile=$1
      shift
      ;;
  esac
  done
  if [ "$selectedIsoFile" == '' ]; then
    failAndExit "Missing argument \`iso-file'."
  fi
  if [ ! -e "$selectedIsoFile" ]; then
    failAndExit "Provided iso file \`$selectedIsoFile' does not exists."
  fi
  typeset mimetype=$(file --mime-type  -b "$selectedIsoFile")
  if [ ! "$mimetype" == "application/x-iso9660-image" ] && [ "$disableMimeCheck" == 'false' ]; then
    failAndExit "Provided file \`$selectedIsoFile' doesn't seem to be an iso file (wrong mime type: $mimetype)."
  fi
}

checkPackages() (
  checkpkg() {
  	if [[ $(which "$1") == "" ]]; then
  		echo -n "Package '$1' not found!"
      if [[ ! $pkgmgr == "" ]]; then
        read -r -n1 -p "Attempt installation? (y/n)>" answer
        echo
        case $answer in
          y) $pkgmgr "$1"
          ;;
          n)
          read -r -n1 -p "Proceed anyway? (y/n)>" answer2
          echo
          if [[ "$answer2" == "n" ]] ; then exit
          fi
          ;;
        esac
      else
        failAndExit "Missing dependency \`$1'."
      fi
  	fi
  }
  for pkg in "${dependencies[@]}"; do
    checkpkg "$pkg"
  done
)

# print the name of the new folder if operation succeeded, fails otherwise
# arg1 : template name
createTempFolder() {
  typeset tmpFileTemplate="/tmp/$1.XXX"
  mktemp -d "$tmpFileTemplate"
  typeset status=$?
  if [ ! $status -eq 0 ]; then
     failAndExit "Failed to create temporary folder"
  fi
}

mountIsoFile() {
  isoMountPoint=$(createTempFolder iso) || exit 1
  echo "Created iso mount point at \`$isoMountPoint'"
  if ! mount -o loop "$selectedIsoFile" "$isoMountPoint"; then
    failAndExit "Could not mount iso file."
  fi
}

selectDrive() {
  typeset drives=()
  typeset _selectedDrive
  containsElement () {
    local e match="$1"
    shift
    for e; do [[ "$e" == "$match" ]] && return 0; done
    return 1
  }
  listDrives() {
    lsblk | grep --color=never -oe "^[sh][a-zA-Z]*"
  }
  chooseDrive() {
    echo "Select the device corresponding to the USB device you want to make bootable (${drives[*]}). Type exit to quit."
    read -r -p "Select device name>" _selectedDrive
    if containsElement "$_selectedDrive" "${drives[@]}"; then
      selectedDrive="/dev/$_selectedDrive"
      echo "Selected device is \`$selectedDrive'"
    else
      if [ "$_selectedDrive" == 'exit' ]; then
        echo "Exiting on user request."
        exit 0
      else
        failAndExit "The drive $_selectedDrive does not exist."
      fi
    fi
  }
  if [ "$selectedDrive" == '' ]; then
    mapfile -t drives < <(listDrives)
    # List all hard disk drives
    echo "Listing available drives in your system:"
    lsblk | grep --color=never -e '^[sh]'
    chooseDrive
  else
    if [[ "$selectedDrive" =~ "/dev" ]]; then
      if [ -e "$selectedDrive" ]; then
        if [[ "$selectedDrive" =~ /dev/[a-zA-Z]+[0-9]+ ]]; then
          failAndExit "\`$selectedDrive' is a partition. Select a drive instead."
        else
          echo "Selected device is: $selectedDrive"
        fi
      else
        failAndExit "The device $selectedDrive does not exists"
      fi
    else
      failAndExit "The selected device is not a valid posix device file (should start with \`/dev')"
    fi
  fi
}

hasDeviceMountedPartitions() {
  typeset result=$(mount | grep -e "^$selectedDrive")
  if [ "$result" == "" ]; then
    return 1
  else
    return 0
  fi
}

partitionUSB() {
  typeset answer
  echowarn "$scriptName is about to wipe out the content of device $selectedDrive."
  selectedPartition="${selectedDrive}1"
  read -r -n1 -p "Are you sure you want to proceed? (y/n)>" answer
  if [ "$answer" == 'y' ]; then
    echo "Erasing contents of $selectedDrive:"
    # unmount
    if hasDeviceMountedPartitions; then
      if ! umount "$selectedDrive"?*; then
        failAndExit "$scriptName failed to unmount paritions from drive $selectedDrive"
      fi
    fi
    # erase drive
    dd if=/dev/zero of="$selectedDrive" bs=512 count=1 conv=notrunc || failAndExit "Failed to erase USB device."
    # set partition
    echo "$selectedPartition : start=2048, type=b, bootable" | sfdisk "$selectedDrive"  || failAndExit "Failed to write USB device partition table."
    # format
    echo "Creating fat32 partition..."
    mkfs.vfat "$selectedPartition" > /dev/null || failAndExit "Failed to create fat32 partition on USB device."
  else
    failAndExit "Discarding operation."
  fi
}

mountUSB() {
  usbMountPoint=$(createTempFolder usb) || exit 1
  echo "Created USB device mount point at \`$usbMountPoint'"
  if ! mount -t vfat "$selectedPartition" "$usbMountPoint"; then
    failAndExit "Could not mount USB device."
  fi
}

createBootableUSB() {
  echo "Copying files from iso to USB..."
  rsync --info=progress2 --recursive --executability "$isoMountPoint"/. "$usbMountPoint"
  if [ "$addSyslinuxBootloader" == 'true' ]; then
    echo "Installing syslinux bootloader..."
    syslinux --stupid "$selectedPartition"
    if [ -d "$usbMountPoint/isolinux" ]; then
      mv "$usbMountPoint/isolinux" "$usbMountPoint"/syslinux
    fi
    if [ -e "$usbMountPoint/syslinux/isolinux.cfg" ]; then
      mv "$usbMountPoint/syslinux/isolinux.cfg" "$usbMountPoint"/syslinux/syslinux.cfg
    fi
  fi
}

main() {
  init "$@"
  parseOptions "$@"
  checkPackages
  selectDrive
  mountIsoFile
  partitionUSB
  mountUSB
  createBootableUSB
}

cleanup() {
  if [ -d "$isoMountPoint" ]; then
    echo "Unmounting iso..."
    if umount "$isoMountPoint"; then
      rmdir "$isoMountPoint"
    fi
  fi
  if [ -d "$usbMountPoint" ]; then
    echo "Unmounting USB..."
    if umount "$usbMountPoint"; then
      rmdir "$usbMountPoint"
    fi
  fi
}

trap cleanup EXIT INT TERM

main "$@"