Booting from a USB device
Linux may be booted from a Live USB, similar to booting from a Live CD. One difference between booting to the USB opposed to the CD is that the data on the USB device may be modified and stored back onto the USB device. When using a Live USB distribution of Linux, you can take your operating system, favorite applications, and data files with you wherever you go. This is also useful if you have problems and are not able to boot your computer for some reason. You may be able to boot the system using the Live USB and access the hard drive and troubleshoot the boot issue.
In order to boot from the USB device, you will need to make the USB device bootable. This requires setting up at least one partition on the USB with the bootable flag set to the primary partition. An MBR must also write to the primary partition on the USB. There are many applications that can be used to create live USB distributions of Linux, including Fedora Live USB Creator and Ubuntu Live USB Creator. The computer may also need the BIOS to be configured to boot from USB.
Some older computers may not have support in the BIOS to boot from a USB device. In this case it is possible to redirect the computer to load the operating system from the USB device by using an initial bootable CD. The bootable CD boots the computer, loads the necessary USB drivers into memory, and then locates and loads the filesystem from the USB device.