Download a debian 8 iso

• Download a debian iso from debian official site

Identify USB drive

identify your usb drive with: fdisk -l OR with lsblk

Format your usb key and flag it as bootable

• install gparted: sudo apt-get install gparted
• format it as fat32(so the drive can be used with windows too) or for linux exclusive usage as ext4
• flag it as boot
• unmount the key
• here is a great resource about partition and flashdrive

Burn it to a usb flash drive

Copy iso file to key using dd (~5 minutes ):

sudo dd bs=4M if=debian-live-8.8.0-amd64-gnome-desktop.iso of=/dev/sdb  && sync 

• eject the key
• restart PC anc check from BIOS that PC will boot from usb devices at first
• install debian

Set up sources.list

The following rows does not deal with a debian flash live install but are important when you install debian whithout internet.

After install from live usb whitout internet, edit as follow /etc/apt/sources.list # deb cdrom:[Debian GNU/Linux 8 Jessie - Official Snapshot amd64 LIVE/INSTALL Binary 20170506-15:01]/ jessie main

#deb cdrom:[Debian GNU/Linux 8 _Jessie_ - Official Snapshot amd64 LIVE/INSTALL Binary 20170506-15:01]/ jessie main

# Line commented out by installer because it failed to verify:
#deb http://security.debian.org/ jessie/updates main
# Line commented out by installer because it failed to verify:
#deb-src http://security.debian.org/ jessie/updates main

deb http://ftp.fr.debian.org/debian/ jessie main contrib non-free
deb http://security.debian.org/ jessie/updates main contrib non-free

Update the package index:

apt-get update

And upgrade packages:

apt-get upgrade

Let's check everything is ok by installing a common packages:

apt-get install -y vim git

sudoerfile

Add the existing ben user to the sudo group:

su
adduser ben sudo