I have to install Ubuntu on a PC and I saw I have to make a bootable LiveUSB from the Ubuntu iso file. However, I can't understand what's the technical difference between making a bootable LiveUSB with a program like Rufus, and copying a .iso file on a USB. Why is not enough to copy it?
If you want to install Ubuntu, you need to make a bootable LiveUSB.
iso is an image of a bootable disk.
If you simply copy an
iso file to a USB disk, you won't be able to boot from it.
A bootable media has specific data in specific sectors, so BIOS or UEFI can start a system from it.
you have to burn it to the flash drive using something like etcher
Creating an UEFI bootable Linux USB stick
We will create a bootable USB stick with Linux by starting from a Linux distribution’s ISO. Since we want to create a USB stick that will be able to boot a UEFI system, we will require an ISO that can do this. The ISO requires a special EFI bootloader.
Make sure that you download the AMD64 version of the ISO! You can download this ISO from the following link: http://releases.ubuntu.com/18.04/ To create the bootable USB stick from the ISO, we use the Rufus tool on Windows. You can download Rufus from official website https://rufus.akeo.ie and version is Rufus 3.3.400 whose size is 995 KB.
Use Rufus as follows:
1. Click “Select” to order to browse to the location of Ubuntu ISO file and select the same.
2. Set “Partition scheme” to “GPT” which is the default partition scheme for UEFI computer.
3. Select “Target system” as “UEFI (non CSM).
4. Set “New Valume Label” as “Ubuntu 18.04.1 LTS amd64 Bionic Beaver”
5. Select “File system” to be “FAT32 (default)”
6. Set “Cluster size” to “4096 bytes (default)”
7. Enable “Qick format” and select “2 passes” as show in the screenshot below.
8. Make sure that Rufus hasn’t changed the partitioning scheme after you have selected the ISO.
9. Click Start button to prepare bootable Ubuntu USB stick.
When Rufus is ready, you will have your USB stick with a UEFI bootloader. Booting a machine with this stick allows you to boot Ubuntu 18.04.1 LTS live session so that you have access to all default Ubuntu utilities. Ubuntu ISO files can be downloaded from the following URL: http://releases.ubuntu.com/
How can I upgrade ubuntu using bootable USB?
You just need to access bios of your PC, and boot from bootable USB, then select "install Ubuntu"
Then a bunch of options will appear (see the image below). Select "upgrade ubuntu" . Done