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Re: Webcam from a chroot?



On Tue, 2007-12-11 at 00:49 +0100, Davide Mancusi wrote:
> Alex Malinovich ha scritto:
> > On Mon, 2007-12-10 at 21:56 +0100, Davide Mancusi wrote:
> >> 	I would like programs inside a 32-bit chroot to be able to access my 
> >> USB webcam, which works fine outside the jail. From the chroot, however, 
> >> it does not work out-of-the-box, nor do I know if it is at all possible 
> >> to do it.
> > 
> > The first thing I'd check is to make sure you that you have /dev
> > and /proc mounted inside the jail. You should have lines similar to this
> > in your /etc/fstab:
> > 
> > proc  /var/chroot/sid-ia32/proc  proc   defaults  0  0
> > /dev  /var/chroot/sid-ia32/dev   none   bind      0  0
> > 
> > (note that the "proc" line does NOT have a / before it)
> 
> 	Interesting. My /etc/fstab looks like this:
> 
> /dev    /var/chroot/sid-ia32/dev  none  bind,auto   0  0
> /proc   /var/chroot/sid-ia32/proc none  bind,auto   0  0
> 
> However, modifying it as you indicated does not help with the webcam. 
> Which version of /etc/fstab is "more correct", now? Binding /proc seemed 
> to make sense to me...

They both work. I prefer to do a regular mount (instead of a bind)
whenever possible, but that's just personal preference. I don't know if
there's any technical reason to do one or the other specifically.

So I don't really know anything about using a webcam as I don't have one
myself, but just on a hunch I checked through the modules for my kernel,
and I found an interesting one:

compat_ioctl32.ko

It caught my eye because it is in kernel/drivers/media/video. I know
that for a brief while when I first moved my system to pure 64-bit, I
had to have an ioctl32 module loaded in order for sound to work within
the chroot. It was something about how the libraries (32-bit) were
talking to the kernel device (64-bit). That ended up getting fixed with
an ALSA update a while ago, but there could be something similar going
on with the webcam.

-- 
Alex Malinovich
Support Free Software, delete your Windows partition TODAY!
Encrypted mail preferred. You can get my public key from any of the
pgp.net keyservers. Key ID: A6D24837

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