ps aux gives me a full listing of everything running on the system, including system processes. Did you mean
Second, you said that
sshd was the only user process running? What about
bash? What about
ps? That's a user process. The number of running user processes really has no reflection on how few system internals are running; that's why the call it a user process and not a system process.
sshd is the only system process running, how does did the computer start up (
init), or deal with TTY connections (
agetty), or log system events (
klogd)? Truth is, there is a very specific reason for each system process and disabling or
kill-ing them can lead to a dumb computer, or a crashed computer.
Udev is pretty much always going to show up in
ps listings on any 2.6.xx system. With the move from Kernel 2.4 to 2.6, the udev subsystem is standard unless you compile your own kernel. If you compile udev support out, then you'll have to rely on an unchecked
/dev structure, which may cause problems.
If you're really looking to use your own minimalistic Linux install, use Damn Small Linux or Linux From Scratch and only install what you want.