This may be necessary for most new portable computers without DVD drives and is handy for others because a USB flash drive is so convenient. Ubuntu can be installed from a USB flash drive. See also: Installation/FromUSBStickQuick for beginners starting from Windows.
#UNIVERSAL USB INSTALLER PERSISTENT FILE SIZE MAC OSX#
Creating a bootable Ubuntu USB flash drive from Mac OSX.mkusb - dd image of iso file to USB device safely.
Install and run Startup Disk Creator alias usb-creator.Creating a bootable Ubuntu USB flash drive from Ubuntu.Pendrivelinux's Universal USB Installer.
Creating a bootable Ubuntu USB flash drive from Windows.