[RESOLVED] Help! - fuse and loopback - not working together

[Greg Freemyer]

The issue is that I was running the fuse mount command as a normal
user and mount as root.

By default fuse does NOT allow root to access filesystems it creates
unless root created them.

For me there are 2 work-arounds:

- Add sudo in front of my command creating the filesytem

- Set an option in /etc/fuse.conf to allow none-owners of a filesystem
to use the filesystem.

I suspect when I did this in the past I was running as root, so I
never noticed the problem.

Sorry for the noise,
Greg
--
Greg Freemyer


On Wed, Dec 3, 2014 at 7:12 PM, Greg Freemyer <greg.freemyer at gmail.com> wrote:
> All,
>
> I don't know if this is a kernel issue or not.  I just don't know
> where else to look for help.
>
> I seem to be having a conflict between fuse and loopback devices.  I
> can get each to work fine independently, but I can get them to work
> together.  This has worked with older kernels, but I can't get it to
> work with a 3.16.6 kernel.
>
> I'm just guessing the issue is a kernel issue.  I really don't want to
> have to compile kernels to track this down, but it may come to that.
>
> All userspace tools I'm using are opensource, so I dod have the
> userspace source to work with, although I'm not the author.
>
> =====
> I'm trying to use a tool (ewfmount) that leverages the fuse kernel
> sub-system to merge several files together and also uncompress them.
>
> Thus I might originally have:
>
> image.E01
> image.E02
> image.E03
>
> where each of those files is a segment of full dd image that has been
> compressed.
>
> If I run "ewfmount image.E01 /mnt" then a virtual file /mnt/ewf1 is
> created.  That is working fine.
>
> In the past I have been able to now loopback mount partitions from
> that virtual file via:
>
> mount -t hfsplus -r -o loop,offset=209735680 /mnt/ewf1 /mnt
>
> Currently that is failing with:
> mount: /mnt/ewf1: failed to setup loop device: Permission denied
>
> Thus loop back seems broken.  To test that I copied the virtual file
> to a real file via dd.  After that mount properly accesses the true
> file.
>
> ===
> Thus:
>
>  fuse is working right to merge my files together and uncompress them.
>
> loopback is working right when the object being mounted is a standard file.
>
> loopback is failing when pointed at the virtual file created by fuse.
> ===
>
> I am suspicious of the kernel because this has worked for me in the
> pastk but with older kernels.  I can't say when it last worked, but at
> least a year ago.
>
> Any suggestions / help appreciated.
>
> Thanks
> Greg
> --
> Greg Freemyer