A SaaS app running in production should be about the size of your binary, and the libraries it uses. Instead, we have X, smtp, terminals and a full filesystem running. home directories and uids make no sense in an app that uses no unix users except for the one you're forced to use.
I'd really like to see a much smaller, simpler, non-posix OS for running server apps.
"OSv was designed from the ground up to execute a single application on top of a hypervisor... OSv... runs unmodified Linux applications (most of Linux's ABI is supported) and in particular can run an unmodified JVM, and applications built on top of one."
1: http://www.linux.com/news/enterprise/cloud-computing/751156-... 2: http://www.openmirage.org/
The POSIX system interfaces (read, write, open, close, etc.) are OK. It's the Commands and Utilities that are the problem. Do you really need Bash available? How much of the 50,000,000 lines of Linux need to be inside your VM running your one web application? How much attack service is provided by the presence of all that stuff?
There's a project which has taken the C runtime library and made it run on a bare VM, so you don't need an OS instance at all. If you're just running one program, that makes a lot of sense.
Second, POSIX is a standard for how the operating system API works that has nothing to do with what packages are installed -- and it's a pretty low-level API, for doing stuff like read, write, fork, exec, etc. This isn't what's adding bloat.