Live USB

A live USB of Ubuntu, running Firefox, OpenOffice.org and the Nautilus file manager.

A live USB is a USB flash drive or a USB external hard disk drive containing a full operating system that can be booted. Live USBs are closely related to live CDs, but sometimes have the ability to persistently save settings and permanently install software packages back onto the USB device. Like live CDs, live USBs can be used in embedded systems for system administration, data recovery, or the testing of operating system distributions without committing to a permanent installation on the local hard disk drive. Many operating systems including Mac OS 9, Mac OS X, Microsoft Windows XP Embedded and many of the Linux and BSD distributions can also be used from a USB flash drive. Windows 8 is also capable of running from a USB drive, with Windows To Go.

History

Since 1999, Apple Macintosh computers (beginning with the Power Mac G4 with AGP graphics and the slot-loading iMac G3 models)[1] have been able to boot from USB. Intel-based Macs support booting Mac OS X from USB.

Specialized USB-based booting was proposed by IBM in 2004, in the papers "Reincarnating PCs with Portable SoulPads" (PDF & Summary) and Boot GNU/Linux from a FireWire device.[2]

Benefits and limitations

A USB flash drive.

Live USBs share many of the benefits and limitations of live CDs.

Benefits

Limitations

Installation

Various applications exist to create live USBs; examples include the WinToUSB (Windows focused), WiNToBootic (Windows focused) or Fedora Live USB Creator and UNetbootin and MultiSystem LiveUSB MultiBoot, which works with a variety of distributions. A few Linux distributions and live CDs have ready-made scripts which perform the steps below automatically. In addition, on Knoppix and Ubuntu extra applications can be installed, and a persistent file system can be used to store changes.

To set up a live USB system for commodity PC hardware, the following steps need to be done:

(Actual use of a CD or DVD will allow the user to choose if the medium can later be written to. Write Once Read Many discs allow certainty that the live system will be clean the next time it is re-booted.)

Knoppix live CDs have a utility that, on boot, allows users to declare their intent to write the operating system's file structures either temporarily, to a RAM disk, or permanently, on disk and flash media to preserve any added configurations and security updates. This can be easier than re-creating the USB system but may be moot since many current (circa 2010) live USB tools are simple to use.

Windows 7 & 8

Although many live USBs rely on booting an open-source operating system such as Linux, it is possible to create live USBs for Windows, for example by using Diskpart or WinToUSB.[8]

Full install

The second type of live USB is closely related to a traditional operating system hard drive install with minor modifications like the elimination of swap partitions and files.

Advantages Disadvantages
  • Updating applications or the whole thing is as easy as the parent distribution used to create it.
  • Full system encryption possible.
  • Easier to customize with the user's preferred Window Manager and applications.
  • Base install usually starts at approximately 200 MB (although some can be as little as 40 MB) and grows as the user adds applications.
  • Due to the additional write cycles that occur on a full-blown installation, the life of the flash drive may be slightly reduced. This doesn't apply to systems particularly designed for live systems which keep all changes in RAM until the user logs off.

Examples of Live USB operating systems

Bootable Windows To Go USB flash drive

Comparison

Distribution Alternatives to live CD creation File saving Application saving Boot methods
Fedora 9 Netinstaller (downloads an ISO image and makes USB), UNetbootin In folder None
Gobolinux Zip + sh and bat scripts N/A N/A 2ram (gobolinux toram)
sidux USB installer GUI In folder, on USB stick Auto Normal
Slax Zip + sh and bat scripts, UNetbootin N/A N/A
SliTaz None and from internal drive ($tazusb) In hacker folder Through script (Tazusb) 2ram - lowram
(K,L,X)Ubuntu UNetbootin Auto Auto
Wolvix None (Control Panel) Auto after making permanent space (Control panel) Auto AllUsb - 2Ram

Syslinux is a program that makes a USB storage device bootable (they are often used after extracting files to the formatted media).

Accessing the BIOS

A message can appear during the POST about a particular key, usually depend upon your BIOS of your computer, that you'll need to press (as soon as the message is seen) to enter Setup. The boot order is a BIOS setting so it's operating system independent. In other words, it doesn't matter if you have Windows 8, Windows 7, Windows Vista, Windows XP, Linux, or any other PC operating system on your hard drive or other bootable device - these boot sequence change instructions will still apply.[13]

See also

External links

Wikimedia Commons has media related to Live USB.
Wikibooks has a book on the topic of: Live distro and Full Linux Install

References