Because, as far as I can tell, docker doesn't make easy reproducible images. How do I make a docker file which will create the same image, bit for bit (at leas

Because, as far as I can tell, docker doesn't make easy reproducible images. How do I make a docker file which will create the same image, bit for bit (at least version for version) in 2 years time? I find usually it's required to update packages, which is good for security, bad for not breaking things.