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Running as SUID root to improving video smoothness
http://forums.linhes.org/viewtopic.php?f=6&t=2615		 Page 1 of 1
Author:  nico_06 [ Thu Oct 07, 2004 3:43 am ]
Post subject:  Running as SUID root to improving video smoothness
Hi!

When I running mythtv with SUID root KnoppMyth hang up when changing Channels...:(


Can anyone help???
Author:  willem [ Fri Oct 08, 2004 1:14 am ]
Post subject: 
My first reaction would be: Don't run it with SUID root then.

Seriously. Why do you want to do that? From the subjectline I understand you want to make the video run smoother. I don't think SUID root would make a difference here (even if you got it working properly).

This forum has lots of suggestions for making video run smoother. Maybe it's your hardware that can't keep up?
Author:  nico_06 [ Fri Oct 08, 2004 2:04 am ]
Post subject: 
2004-10-08 10:01:04 Running as SUID root would allow some threads to run with realtime priority, improving video smoothness.

this is my mythfrontend log output...

It also stand in the new mythtv documentation...

I hav written mythtv but I mean mythfrontend...:)
Author:  Liv2Cod [ Fri Oct 08, 2004 10:58 am ]
Post subject: 
I've tried to get this to work, too, without success.

If I use "chmod u+s /usr/bin/mythfrontend" my system completely hangs when I try to play a recorded show. I tried adding it to /etc/sudoers but that seems to do nothing.

My system still taunts me with:

Code:
2004-09-27 01:05:23 Running as SUID root would allow some threads to run with realtime priority, improving video smoothness.
Author:  sootzoo [ Fri Oct 08, 2004 12:06 pm ]
Post subject: 
Basically, a normal user cannot raise the priority of a process (beyond a certain point), but if the frontend runs SUID root, it will help synchronization a bit since, say, the video and sound IO calls are able to do their jobs without waiting on another process to finish with the CPU.

If you're simply doing a chmod u+s on a file, when run, it will execute with the permissions of that file's owner no matter who is running it. But isn't ownership of mythfrontend usually "myth" or something similar (a normal user)? I *believe* if you chown the file to root, set u+s on the file, and make sure everyone (or at least a group containing your myth user) can read/execute the frontend program, then it will run SUID root and stop pestering you.
Author:  khrusher [ Fri Oct 08, 2004 1:04 pm ]
Post subject: 
sootzoo wrote:
If you're simply doing a chmod u+s on a file, when run, it will execute with the permissions of that file's owner no matter who is running it.


I dont think this is correct. It's the process that has the priority, not the file. If a process owned by the root user is running at a raised priority, that priority is in effect for every operation/command it executes.
Author:  sootzoo [ Fri Oct 08, 2004 1:09 pm ]
Post subject: 
You're right, I ran into this rebuilding sendmail some months ago, which likes to run SGID, but the file is still owned by the sendmail user.

My apologies.
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