Live USB - Principle of Installation

Principle of Installation

Various applications exist to create live USBs; examples include the WiNToBootic (Windows focused) or Fedora Live USB Creator and UNetbootin and MultiSystem LiveUSB MultiBoot, which works with a variety of distributions. A few Linux distribution 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:

• A USB flash drive needs to be connected to the system, and be detected by it
• One or more partitions may need to be created on the USB flash drive
• The "bootable" flag must be set on the primary partition on the USB flash drive
• An 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 file 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

(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.