Live USB

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A live USB or USB live distro is a USB flash drive or an external hard disk drive containing a full operating system which can be booted. Live USBs are closely related to live CDs, and are sometimes used interchangeably. Like live CDs, live USBs can be used in embedded systems 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 Microsoft Windows XP Embedded and many of the smaller Linux distributions can also be used from a USB flash drive.

Contents 1 Benefits and limitations 2 Principle of installation 3 History 4 Types of live USB 4.1 Live CD derived 4.2 Full install 5 Examples 6 Comparison 7 See also 8 External links 9 References

[edit] Benefits and limitations

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

Live USB distros can be run from the portable flash device in the same fashion (but much faster) than it would from the live CD. One important advantage over live CDs is the ability to conveniently change the data contained on the booting device. This allows for live USBs to be used as personal storage, as it allows a user to carry their preferred operating system, applications, files and configuration with them, making it easy to share a single system between multiple users.

Live USBs provide the additional benefit of enhanced privacy, because the user can easily carry the USB device with them or store it in a secure location (e.g. a safe) reducing the opportunities for others to access their data. On the other hand, usually it is easy for an USB device to get lost or stolen, so data encryption and backup is even more important than with a typical desktop system.

The absence of moving parts in USB flash devices allows for faster seek time than is possible with hard drives or optical media, meaning small programs will start faster from a USB flash drive than from a local hard disk or live CD. However, as USB devices typically achieve lower data transfer rates than internal hard drives, booting from a computer lacking USB 2.0 support can be very slow.

Some computers, particularly older ones, may not have a BIOS that supports USB booting. In this case a computer can often be "redirected" to boot from a USB device through use of a bootable CD or floppy disk. ^[1]

Due to the additional read/write cycles that occur on a full blown install, the life of the flash drive may be slightly reduced.

[edit] Principle of installation

Various applications exist to create live USBs; examples include the Fedora Live USB Creator and UNetbootin, which works with a variety of distributions.

To install a live USB system on a memory stick the following steps need to be done:

• A USB flash drive needs to be connected to the system, and be detected by it
• One or more partitions must be created on the USB flash drive
• the "bootable" flag must be set on the primary partition on the USB flash drive
• A MBR must be written to the primary partition of the USB flash drive
• The partition must be formatted (most often in FAT32 format, but other systems can be used too)
• A bootloader must be installed to the partition (most often using syslinux when installing a Linux system)
• A bootloader configuration file (if used) must be written
• The necessary files of the operating system and default applications must be copied to the USB flash drive
• language and keyboard files (if used) must be written to the USB flash drive

In addition, on some Live distros, extra applications can be installed, and a persistent file system can be used to store changes.

[edit] History

• Proposed by IBM in 2004, in the papers "Reincarnating PCs with Portable SoulPads" (PDF & Summary) and Boot Linux from a FireWire device

[edit] Types of live USB

[edit] Live CD derived

The first type of live USB was created by simply taking the ISO image file from a live CD distribution and placing it on USB storage device and then making it bootable.

Advantages	Disadvantages
Simple to install.[citation needed] Compressed format allows for many applications in a small storage container.[citation needed] Updating whole image file is as easy as copying in a new one.[citation needed] Base installation can be as small as 50mb.	Difficult to update individual applications or install applications not part of the original image. Base install maximum size can be 700MB to 4GB for large installs. Many live CDs are not set to write to their own filesystem as a CD is typically read only, thus it can sometimes be difficult to enable a live USB OS to write to its flash drive. Encryption is only on a 'per-file' basis.

[edit] 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 customise with the user's preferred Window Manager and applications. Base install usually starts at approximately 200MB (although some can be as little as 40MB) and grows as the user adds applications.	Only easy to install if the operating system provides support. Will wear through the USB faster.

[edit] Examples

• BackTrack
• BeleniX: Customized OpenSolaris installs including live CD and live USB.^[2]
• Damn Small Linux: Knoppix derived small installation, uses a 2.4 kernel, with JWM as default user interface.
• Debian ^{[3] [4]}
• Dyne:bolic: 100% free distribution for multimedia production, boots from CD and USB stick, with Xfce as default user interface.
• FaunOS: a live USB distribution based on Arch Linux
• Fedora (with Fedora Live USB creator)
• Gentoo ^[5] Gentoo USB Live.
• Knopperdisk: A small distribution based on Gentoo but designed to be run from USB pen drives or floppy disks.
• MCNLive: Mandriva derived live CD, and live USB distribution.
• MilaX: Small OpenSolaris live CD and live USB distribution.
• Minix ^[6]
• NimbleX: A small (200mb) distribution based on Slackware.
• OpenSolaris: The Distribution Constructor project has tools allowing users to build an install image.^[7]
• PCLinuxOS
• OSx86 ^[8]
• Pentoo: Gentoo based live CD and live USB distribution focused on penetration testing and security assessment.
• Puppy Linux Designed for easy install on USB.
• RUNT Linux: Based on Slackware with a 2.4 kernel and Umsdos filesystem. Designed as a network testing tool for students at North Carolina State University.
• sidux: Based on Debian unstable (sid)
• Slax: Slackware based installation.
• Ubuntu (can be installed directly to a flash drive or USB external Hard Drive manually or using tools like the Ubuntu Live USB creator or UNetbootin)
• Windows Preinstallation Environment: Freely available version of a live Windows installation, command line only.

[edit] Comparison

Distribution	Alternatives to live Cd creation	File saving	Application saving	Boot methods
Fedora 9	Netinstaller (downloads iso & makes Usb), UNetbootin	in folder	none
Goblinux	Zip + sh&bat scripts	N/A	N/A	2ram (goblinx toram)
sidux	USB installer	in folder	auto	normal
Slax	Zip + sh&bat scripts, UNetbootin	N/A	N/A
SliTaz	none & from internal drive($tazusb)	in hacker folder	trough script (Tazusb)	2ram - lowram
(K,X)ubuntu	UNetbootin	auto	auto
Wolvix	none (Control Panel)	auto after making permanent space (Control panel)	auto	AllUsb - 2Ram

Sh (for linux) & bat (for windows) are scripts that make a usb storage device bootable (they are often used after extracting files to the formatted media)

[edit] See also

• Extensible Firmware Interface
• extlinux
• Live Distro
• Comparison of Linux Live Distros
• Disk cloning
• List of Live Distros
• Persistence (computer science)
• List of tools to create Live USB systems

[edit] External links

• pendrivelinux

[edit] References

v • d • e The Linux operating system General Adoption · Comparison of Windows and Linux · Criticism · GNU Project · History · Linux Foundation · Kernel (portability) · Linus's Law · GNU/Linux naming controversy · Tux Linux portal Distribution Distribution (comparison) · Live CD (comparison) · Live USB · Mini Linux · Package formats Applications ALSA · Desktop · Devices · Embedded · Gaming · LAMP · Proprietary · Thin client People Jono Bacon · Alan Cox · Benjamin Mako Hill · Pamela Jones · Ari Lemmke · Andrew Morton · Ian Murdock · Hans Reiser · Scott James Remnant · Daniel Robbins · Mark Shuttleworth · Richard Stallman · Linus Torvalds · Theodore Ts'o · Patrick Volkerding · Warren Woodford · Matt Zimmerman Media Enterprise open source journal · Free Software Magazine · Linux.com · Linux Format · Linux Gazette · Linux Journal · Linux-Magazin · Linux Magazine · LWN.net · O3 Magazine · Phoronix Lists Devices · Distributions · Live Distros Mobile Access Linux Platform · Android · LiMo Platform · Mobilinux · Moblin project · Ubuntu Mobile and Embedded Edition · Linux Phone Standards Forum Other topics Linux malware · Linux User Group (LUG) · Linux Standard Base · Revolution OS · SCO and Linux · Tanenbaum-Torvalds debate