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Old 10-17-2011, 10:13 PM   #1
ajaygarg
Member
 
Registered: Mar 2010
Location: New Delhi, India
Distribution: Fedora
Posts: 94

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Query regarding ownership permissions for /dev "files"


Hi all.

I am wanting to disable my laptop camera (for everyone), on a Fedora 14 system.

I am an absolute newbie, and after some googling, I found that /lib/udev/rules.d/50-udev-default.rules was my file. I changed the line

Code:
SUBSYSTEM=="video4linux",       GROUP="video"
to

Code:
SUBSYSTEM=="video4linux",       GROUP="video", MODE="0000"
After rebooting, and doing ls -l /dev/video0, the output had changed from
Code:
crw-rw----+ 1 root video 81, 0 Oct 18 08:27 /dev/video0
to

Code:
c---rw----+ 1 root video 81, 0 Oct 18 08:27 /dev/video0
Saw the wonder? Apparently, there was an effect by changing the 50-udev-default.rules file, but there was still a rw permission for the group "video".


So, I did more googling, and arrived at /etc/security/console.perms.d/50-default.perms. This file didn't exist already. So, I created one, and it now looks like
Code:
<video>=/dev/video*
<console> 0000 <video> 0000 root
I again rebooted, but ls -l /dev/video0 still shows
Code:
c---rw----+ 1 root video 81, 0 Oct 18 08:27 /dev/video0
Anything else, that I may give a try?

Regards,
Ajay
 
Old 10-17-2011, 11:13 PM   #2
Seven_Six_Two
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Registered: Nov 2007
Posts: 5

Rep: Reputation: 1
Thumbs up Re: Query regarding ownership...

I'm not a Fedora user, but my suggestion would be to use(as root)
modprobe -r <cam_module>
and then blacklist that module by adding a line to /etc/modprobe.d/blacklist.conf
blacklist <cam_module>
Just so we're clear, you'll have to replace <cam_module> with the name of your actual module.
You can get a list of modules in use with the command
lsmod
although you might have to use Google to figure out which one to remove. Mine is called uvcvideo, so I would do this:
# modprobe -r uvcvideo
Be careful. Have a live cd on hand just in case. Playing with modules can cause instability, crashes, and can make your system unbootable.
 
1 members found this post helpful.
Old 10-18-2011, 02:21 PM   #3
ajaygarg
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Registered: Mar 2010
Location: New Delhi, India
Distribution: Fedora
Posts: 94

Original Poster
Rep: Reputation: 0
Thumbs up

Thanks seven_six_two.

You provided enough information to solve my query. Thanks a ton.

In my case, adding the entry to "/etc/modprobe.d/blacklist.conf" (followed by rebooting) was enough, as it provided with the following two advantages :

1. The best solution, as it disabled the driver (lowest level solution possible).
2. This did not require any addition/removal of anything, only disabling of the driver.

As the root access is to be disabled, so this provides the cleanest, most efficient solution.

Thanks again seven_six_two.

Regards,
Ajay

Last edited by ajaygarg; 10-18-2011 at 02:24 PM.
 
  


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