Re: [Qemu-devel][PATCH] qemu-fuse

[Anthony Liguori <anthony@codemonkey.ws>]

Shahar Frank wrote:
> Hi All,
>
> 	The attached is a small utility to mount qemu images as pseudo
> partition files. It can be very useful to access (rw) images from the
> host.
> I would not use it for production, but it seems to be stable.
>   

Heh, quite similar to:

http://hg.codemonkey.ws/qemu-img-mount/file/9f11265882b3/qemu-img-mount.diff

So this was my first approach to solving this problem that I ended up 
abandoning in favor of qemu-nbd (which is now in the tree).  The main 
limitation I found with fuse is that by default (and it takes a lot to 
change this), fuse filesystems are unreadable by root.  This means that 
you cannot easily mount -oloop something in a fuse filesystem.

What I really wanted, was the ability to say something like:

qemu-img mount -p1 foo.img /mnt

and it would Just Work.  The only two options I found that could make 
this work is:

1) disable the root readable limitation in fuse, this has to be done 
globally and I suspect is unlikely to be done by distros.

2) add support to qemu-img-mount to use filesystems libraries like 
libe2fs to read and present the filesystem contents.  This has the 
advantage of working entirely as the user who issues the command but has 
the disadvantage of requiring a lot of effort without being able to 
support all filesystems that Linux supports.

So that's why I settled on qemu-nbd.

Regards,

Anthony Liguori