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  • From: "Anthony J. Albert" <albert AT polaris.umpi.maine.edu>
  • To: baslinux AT lists.ibiblio.org
  • Subject: Re: [BL] User task vs Kernel task
  • Date: Fri, 20 Feb 2004 09:16:44 -0500

On 20 Feb 2004 at 9:53, Nguyen The Luan wrote:
>Hi All
>In Linux OS, we have 2 spaces: user space and kernel space.
>User space tasks has lower priviledges and priority than kernel space tasks.
>But kernel tasks are not able to get input from user, printf, read/write
>files...

Actually, kernel tasks are able to do these things - they just normally
don't, with the exception of read/write files.

>So My question is:
>How can we make our user space tasks have priviledges and priority like
>kernel task.
>It means that our user space tasks not only communicate with users but also
>do anything that kernel tasks can do.
>In other words, How to change Linux system from multiuser, multitasking to
>single user multitasking system.
>
>Best regards
>Nguyen

For the most part, there is never a need to do this. The Unix design
is such that, for the tasks that the user needs to do that are in
"kernel space", there's a call to the kernel. This is so that user-
space tasks which misbehave don't bring the whole system down - the
kernel has a chance to force the process to exit.

I would recommend looking for a good book on operating system design,
if you'd like more detail on why having kernel space and user space
separate is a "good thing".

You can change to a single-user system, though, if you really want to.
Most Linux allow you to set the runlevel, usually in /etc/inittab .
Editing the line:
id:3:initdefault:
to have an "S" or a "1" instead of a "3" will likely bring your system
up in single-user mode, after rebooting.

Don't know if everything will work, though, as many programs are only
set to run at certain bootlevels.

Hope this is helpful,
Anthony Albert
===========================================================
Anthony J. Albert albert AT umpi.maine.edu
Systems and Software Support Specialist Postmaster
Computer Services - University of Maine, Presque Isle
"This is only temporary, unless it works."
--- Red Green





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