So how do you get your servlets to violate security
rules for Unix and Linux? You can't; you'll need to make
some other arrangement. Here are some possibilities:

• Run the servlet engine as root. This is dangerous.


• Create some external programs or scripts that have
  setuid privileges, and invoke those programs with
  Runtime.exec() calls. Depending on what those programs
  do, this could be pretty dangerous also.


• Write an external setuid program that works like
  "su" - taking a username and a password that you'd
  collect from the user - and executing the requested command
  if the username and password are good. The "su" program
  is not an exact fit, because it expects you to type a password
  in on a tty, but something based on "su" would do the trick.

What these all have in common is that some code
needs to run, at least temporarily, with extraordinary privileges -
so you can't do this on a system with an uncooperative
sysop. But that's the nature of security in a real OS
like Linux - you don't give everyone the power to
do damage.