I am doing a course on embedded systems, and I need to install Ubuntu for that. While searching the web for doing so I came across two forms in which the Ubuntu software is downloaded, namely the virtual disk image (VDI) and the ISO file formats. May I know the difference between these two file types?
A VDI file
file.vdiis a file, that is made for virtual machines. It is typically used to provide a virtual file system by VirtualBox, where Ubuntu and other operating systems can be installed in a virtual machine.
VirtualBox is an application program, that runs in a host operating system (for example Ubuntu or Windows). You create a virtual machine, and a VDI file to provide an 'internal disk' in the virtual machine, where you install a guest operating system. This link shows some useful details.
Please notice that you can boot a virtual machine directly from an iso file.
An iso file
file.isois a file, that is made in order to create a bootable drive in a CD/DVD disk and/or a mass storage device (usually a USB pendrive or memory card but also an SSD or HDD). The partition structure and file system is iso 9660, which is read-only, and the idea is to copy/expand the stored file system into RAM, to run the operating system.
Most main linux distros, including Ubuntu, provide hybrid iso files, which can be burned to a DVD disk and cloned to a mass storage device (usually a USB pendrive) and the result will be a bootable drive, that will run a live-only version of the operating system for testing and/or installing the operating system into an internal drive in the computer.
This link helps with some more details.