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Re: Webcam from a chroot?



On Mon, Dec 10, 2007 at 05:54:54PM -0800, Alex Malinovich wrote:
> 
> 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.

What happens if you use schroot?  I don't have a webcam to try, but
schroot handles mounting everything I need; no need for /etc/fstab
entries for it.

Doug.



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