[plug] loopback

[Jim Householder]

Cameron Patrick wrote:
> Jim Householder wrote:
> 
> 
>>$ mount file.iso /distros/loop0-t iso9660 -o loop=/dev/loop0
>>which works nicely under Mdk 10, but gives me
>>ioctl: LOOP_SET_FD: Device or resource busy.
> 
> 
> Looking at the kernel source, the most likely cause for that error is
> that /dev/loop0 is already in use.  That's okay, though, because there

In hindsight it should have been obvious - Device busy -- /dev/loop...

> are (by default) 8 loop devices, which is enough for most people.  (It
> can be increased further with the max_loop option to the loop module,
> for those occasions where you feel like doing freaky things with loop
> mounts.)  Normally you just specify '-o loop' without naming a device
> and it'll find the first free loop device.
> 
Bingo!  Thanks.
> 
>>Also, the command is rejected if not issued by root.
> 
> 
> That's normal.  Only root can mount or unmount things (with a few
> exceptions, e.g. devices listed with the 'user' option in /etc/fstab).
> 
> Loop-mounting an arbitrary filesystem - even onto a mount point that
> you own - can be a security hole.  Consider the case of creating an
> ext2 filesystem image with a setuid copy of bash on it, copying it to
> someone else's machine and loop-mounting it somewhere.
> 
> Cameron.
>