The OP (who may still actually be alive) asked for someone to "briefly explain the process of creating and installing images of Linux systems." There are many such processes. To keep it "brief," we should perhaps try to narrow it down.
The title specifies that this is to be an image of a running Linux system. My understanding is that an image of a running system is problematic, because Linux does not have a Volume Shadow Copy feature like Windows has. Files may be in use, and may therefore not be copied correctly, or at all.
Systemback is one of the few surviving tools that at least try to take an image of a running system. I found it somewhat frustrating, but I think that may be because I was using it in a relatively constrictive virtual machine setting. It is pretty much self-explanatory, and there are tutorials available. But, briefly, it requires a two-stage process: use it to create a .sblive file, and then use that file to create an ISO or image file or to burn to a drive.
Other tools avoid the Volume Shadow Copy issue by creating an image when the system is not running. Clonezilla is probably the best-known example. You boot the computer with a Clonezilla bootable USB drive (or similar tool), and then work through Clonezilla's menu, answering questions for your specific situation. Here, too, there are tutorials.
I didn't particularly like Clonezilla's style. To me, it made things some things simpler and other things more complicated. For me, the preferred solution (in converting an Ubuntu virtual machine to a physical drive) was to boot another Linux ISO, use it to run a command that would create a .gz image file of the Ubuntu system (which was not running), and then use it to run another command that would restore that .gz file to a target drive. The commands I used were as follows:
sudo dd if=/dev/sda bs=16M conv=sync,noerror | pv | sudo pigz -c > /media/lubuntu/SSD/UbuntuImage.dd.gz
and then
sudo pigz -cdk /media/lubuntu/1TB/UbuntuImage.dd.gz | pv | sudo dd of=/dev/sdb bs=16M
Those require pv and pigz to be installed on the alternate Linux ISO. The whole process wasn't bad -- I would even say it was simpler than Systemback, once I figured it out -- but it did take some effort to assemble the pieces, and of course the commands were powerful: specifying the wrong drive could wipe out its contents entirely. In the interests of keeping this answer "brief," I won't overwhelm the casual reader with the full details, pointing instead to my detailed writeup elsewhere.
