I have burnt Ubuntu Desktop onto a USB that is currently plugged into the Ubuntu server 12.10. I would like to know how I can run the install from the USB as no other ways work.
Download the iso that you want to install from ubuntu.com. Install the Ubuntu Startup Disk Creator from the terminal by running:
sudo apt-get install usb-creator-gtk
The Startup Disk Creator has a self-explanatory graphical user interface for creating a bootable Ubuntu live USB flash drive from an Ubuntu ISO file. The USB flash drive that you use with Startup Disk Creator should be 2GB or larger, and for Ubuntu 18.04 and later it should be 4GB or larger. Startup Disk Creator will automatically format your USB flash drive to FAT32 and make it bootable. If you have only one USB flash drive plugged in to your computer, Startup Disk Creator will select it automatically.
It is very important to identify the USB flash drive that you are writing the Ubuntu Startup Disk to correctly so that you don't overwrite any of your system files which may make your operating system unbootable. Ubuntu can be installed easily from an Ubuntu Startup Disk live USB. After you have booted the Ubuntu Startup Disk, you will see an Install Ubuntu icon on the desktop that you can double-click to start the Ubuntu installation procedure.
In order to enable your computer to boot from the USB flash drive, you must enter your BIOS menu by pressing one of these keys: Delete, F2 or F10 as soon as the motherboard splash screen appears when the computer is booting. In the BIOS menu, you need to change the boot order so that the USB flash drive, which is usually called USB-HDD in newer computers, is the first entry in the boot sequence, and then save your new BIOS settings and exit the BIOS setup.
Reboot and pick the USB Flash drive from the list of bootable devices, normally there is an bootable device list that can be selected by pressing a function key usually F11 but that varies between manufacturers of motherboards. If that doesn't help go into your BIOS and make sure the USB drive is the first bootable device.