[MUSIC] Now, root or administrator privileges
usually work a little bit differently, especially on Linux. What happens with Linux is
the designers of Linux realized early on that when someone became
the administrator, they could do anything. So they adopted a technique from very high
assurance systems in which these rights or privileges are parceled out separately. So, for example, if I am root, and I have the capability to delete files,
I can't go and read your files. I can only delete certain files. This is called capabilities and there's a technical definition,
which I won't go into. But basically, capability in this
context is something that allows a process to do an action that it
would not normally be allowed to do. For example,
if I want to read a file a certain file, if I have a capability to read that file,
I can do it as myself. I don't need, say,
your ID privileges at all to do it. So the capabilities, first of all, provide a very tight restriction on
what privilege the user is given. And secondly, they allow me to remain with everything
else at my usual privilege level. And Linux FreeBSD and a number of
other systems have these capabilities, and the exact nature of the capabilities
differs from system to system. But, in general, they're for
file manipulation, or inter-process communication,
or things like that. Okay, now how do capabilities work? Well, there are many
different implementations. For example, with Linux, when a process
runs, it has three sets of capabilities, permitted ones, effective ones,
and inheritable ones. The permitted ones are the set of
capabilities it starts up with. When it spawns a sub-process, some of
those capabilities are inheritable. And those capabilities will be inherited
by the sub-process, some of them aren't. The effective capabilities are the ones
that the process is actually using. So the difference between permitted and
effective is permitted means you can do it, effective means you are doing it, and
inheritable means you're passing them on. FreeBSD is Unix that uses
capabilities as well. By default, those capabilities are turned
off, so you have to turn them on yourself. The administrator has to turn them on. And they are inherited
by the child process. There is no notion of an inheritable set. All of the capabilities that
the parent has go to the child. So the bottom line is if your
system supports capabilities, read the manual pages very carefully so
you know how they work.