A tar process that won't die!

[Mitch Patenaude]

Assuming that the problem is something simple like you don't have 
permission to kill the process, then the problem is that the process 
isn't in a state where it "CAN'T" die.

Processes in Unix (and Linux) can be running in one of two modes.  
User-mode is where most of your code runs, and is interuptable, and can 
be killed.  But a process can also run in kernel mode.  This usually 
happens when you're interacting with hardware, or you've called a system 
call (open(2), write(2), read(2), fork(2), etc.) which needs to work on 
stuff inside the kernel.  While in kernel mode, a process can't be 
killed, because it would compromise system integrity.
So, if tar can't be killed, it's likely that it's running in kernel 
mode, and given the nature of tar, it's probably stuck in an I/O call.  
As soon as it returns from that call, it will die, but that might be a 
while, maybe never if there is a problem with the driver.

All this doesn't point directly to an answer, but it might give you 
someplace to look.  If it were merely writing a very long buffer using 
write(2), then it might eventually finish.  If however, the io call is 
blocked because of some external factor, say a zip disk which has been 
removed, and the driver is waiting for the drive to signal ready, or 
something like that, then maybe you can resolve it by figuring out what 
the process is hung up on.

Or... just reboot.. and that will solve the problem. :-)

    -- Mitch