Container ~= process which has been isolated from the host system using linux specific kernel features. If you launch systemd and all ubuntu services, yes, it w

Container ~= process which has been isolated from the host system using linux specific kernel features. If you launch systemd and all ubuntu services, yes, it will effectively run the whole os, otherwise, it's just a process like any other with no overhead. Why the image? Well it contains the filesystem of your container - all the libraries your process needs to convert its' logic to kernel syscalls, all in their own filesystem bubble, so there are no clashes, wrong versions, etc.