View source for Engineering:USB image

A '''USB image''' — is [[BIOS#Boot process|bootable]] [[ISO image|image]] of [[Operational system|Operating system]] (OS) or other software where the [[Boot loader|boot loader]] is located on a [[Engineering:USB flash drive|USB flash drive]], or another USB device (with memory storage) instead of conventional [[Engineering:CD|CD]] or [[Engineering:DVD|DVD]] discs. The [[Operating system|operating system]] loads from the USB device either to load it much like a Live CD that runs OS or any other software from the storage or installs OS itself. USB image runs off of the USB device the whole time. A USB image is easier to carry, can be stored more safely than a conventional [[Engineering:CD|CD]] or [[Engineering:DVD|DVD]]. Drawbacks are that some older devices may not support USB booting and that the USB storage devices lifespan might be shortened.

Ubuntu has included a utility for installing an operating system image file to a USB flash drive since version 9.10.<ref>[https://help.ubuntu.com/community/Installation/FromUSBStick Ubuntu documentation: Installation: Installation/FromUSBStick]</ref> Windows support also has added a step by step on how to set up a USB device as a bootable drive.<ref>{{Cite web|url=https://support.microsoft.com/en-us/help/4075119/surface-windows-81-boot-surface-from-a-usb-device|title=Boot Surface from a USB device|website=Microsoft support|access-date=29 April 2019}}</ref>

== Software ==

Both graphical applications and command line utilities are available for authoring bootable operating system images. [[Software:Dd (Unix)|dd]] is a utility commonly found in [[Software:Unix|Unix]] operating systems that allow creation of bootable images.<ref>{{Cite web|url=https://www.cyberciti.biz/faq/unix-linux-dd-create-make-disk-image-commands/|title=How to make disk image with dd on Linux or Unix|website=nixCraft}}</ref>

== Benefits and limitations ==

=== Benefits ===

* In contrast to live [[Engineering:CD|CD]]s, a USB image is easier to transport and to store (e.g. a pocket, attached to a key chain, carried in a bag, locked away in a safe), instead of a [[Engineering:CD|CD]], which can be damaged and corrupted easier, and also harder
* Also after OS installation, the USB can be removed after installation, and the operating system will run without the USB stick inserted into the computer, allowing installation on multiple [[Operating system|OS]] devices with a single USB (This is known for Win 8.1 and newer Microsoft Win versions, since they fully support the USB image installation)
* The absence of moving parts in USB flash devices allows true [[Random access|random access]] avoiding the rotational latency and seek time, 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 older computers that lack [[Engineering:USB|USB 2.0]] or newer can be very slow.

=== Limitations ===

* Some older systems have limited support for USB, since their [[BIOS|'''BIOS'''es]] were not designed with such purpose at the time. Other devices may not be booted from USB, if in BIOS it is set to 'Legacy mode'[[Legacy mode]].
* Due to the additional write cycles that occur on a full installation, the life span of the used USB may be shortened.<ref>{{Cite web|url=https://forums.linuxmint.com/viewtopic.php?f=46&t=16243?f=46&t=16243#p141498|title=XFCE minimum install HD?|website=forums.linuxmint|access-date=29 April 2019}}</ref> To mitigate this, a USB hard drive can be used, as they give better performance than the USB stick, regardless of the connector.

== See also ==

* UEFI
* [https://www.osforensics.com/tools/write-usb-images.html ImageUSB] (Per Partition or mounted Drive)
* [[Software:Live USB|Live USB]]

== References ==
{{Reflist}}

[[Category:Booting]]



{{Sourceattribution|USB image|1}}