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Re: [Qemu-devel] Idea: fuse-kvm filesystem
From: |
Avi Kivity |
Subject: |
Re: [Qemu-devel] Idea: fuse-kvm filesystem |
Date: |
Thu, 10 May 2012 15:55:17 +0300 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 |
On 05/10/2012 03:35 PM, Richard W.M. Jones wrote:
> On Thu, May 10, 2012 at 03:29:54PM +0300, Avi Kivity wrote:
> > Currently when you mount a filesystem, you face two issues:
> > - you have to be root
> > - if the media is untrusted, it can exploit your kernel
> >
> > With kvm and fuse, we can have a virtualized kernel mount the
> > filesystem, and re-export to the host, which mounts it using a fuse
> > interface. This solves both problems, at the expense of speed and
> > simplicity. In theory this can be used for mounting untrusted USB
> > sticks (perhaps only for the less well tested filesystems).
>
> I guess you CC'd me so I could point out guestmount :-?
>
> http://libguestfs.org/guestmount.1.html
Is there a feature that libguestfs doesn't have?
Anyway I tried it out and it seems to work really well.
> guestmount does the above already, and you can point it directly at
> USB sticks, hard drives and the like, although most people use it for
> mounting VM filesystems on the host.
>
> On my local machine I'm a member of the "disk" group so I can do all
> this as non-root:
>
> $ guestmount --ro -a /dev/vg_pin/F16x64 -i /tmp/mnt
> $ cat /tmp/mnt/etc/redhat-release
> Fedora release 16 (Verne)
> $ ls /tmp/mnt
> bin dev home lib64 media opt root sbin srv tmp var
> boot etc lib lost+found mnt proc run selinux sys usr
>
> One problem you'll find is that FUSE is pretty slow. I recommend if
> you're looking for performance that you use the libguestfs API calls
> directly instead of POSIX-over-FUSE.
Yes, 'guestmount' consumes a fair bit of cpu. But it probably doesn't
matter for USB sticks.
--
error compiling committee.c: too many arguments to function