Libguestfs - Jul 2017 - Re: performance between guestfish and qemu-nbd

2017-07-27 20:18 GMT+08:00 Richard W.M. Jones <rjones@redhat.com>:
> On Thu, Jul 27, 2017 at 06:34:13PM +0800, lampahome wrote:
> > I can mount qcow2 img to nbd devices through guestfish or qemu-nbd
> >
> > I'm curious about which performance is better?
>
> They do quite different things, they're not comparable.
>
> Can you specifically give the commands you are trying?  We might be
> able to give more sensible advice.
>
> Rich.
>
> --
> Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~
> rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
> Fedora Windows cross-compiler. Compile Windows programs, test, and
> build Windows installers. Over 100 libraries supported.
> http://fedoraproject.org/wiki/MinGW
>
guestfish:
guestfish --rw -a demo.qcow2 -m /dev/nbd0

qemu-nbd:
qemu-nbd -c /devnbd0 demo.qcow2

I just want to mount demo.qcow2 to a device

On Fri, Jul 28, 2017 at 12:23:04AM +0800, lampahome
wrote:
> 2017-07-27 20:18 GMT+08:00 Richard W.M. Jones <rjones@redhat.com>:
> 
> > On Thu, Jul 27, 2017 at 06:34:13PM +0800, lampahome wrote:
> > > I can mount qcow2 img to nbd devices through guestfish or
qemu-nbd
> > >
> > > I'm curious about which performance is better?
> >
> > They do quite different things, they're not comparable.
> >
> > Can you specifically give the commands you are trying?  We might be
> > able to give more sensible advice.
> 
> guestfish:
> guestfish --rw -a demo.qcow2 -m /dev/nbd0
>
> qemu-nbd:
> qemu-nbd -c /dev/nbd0 demo.qcow2
These don't do the same thing.  In fact the guestfish command doesn't
work at all.
> I just want to mount demo.qcow2 to a device
Still unclear.

You want to export demo.qcow2 as NBD?  Use qemu-nbd.

You want to mount demo.qcow2 on the local filesystem?  (This doesn't
involve NBD.)  Use:

  mkdir /tmp/mnt
  guestmount --rw -a demo.qcow2 -i /tmp/mnt

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine.  Supports Linux and Windows.
http://people.redhat.com/~rjones/virt-df/

2017-07-28 0:31 GMT+08:00 Richard W.M. Jones <rjones@redhat.com>:
> On Fri, Jul 28, 2017 at 12:23:04AM +0800, lampahome wrote:
> > 2017-07-27 20:18 GMT+08:00 Richard W.M. Jones
<rjones@redhat.com>:
> >
> > > On Thu, Jul 27, 2017 at 06:34:13PM +0800, lampahome wrote:
> > > > I can mount qcow2 img to nbd devices through guestfish or
qemu-nbd
> > > >
> > > > I'm curious about which performance is better?
> > >
> > > They do quite different things, they're not comparable.
> > >
> > > Can you specifically give the commands you are trying?  We might
be
> > > able to give more sensible advice.
> >
> > guestfish:
> > guestfish --rw -a demo.qcow2 -m /dev/nbd0
> >
> > qemu-nbd:
> > qemu-nbd -c /dev/nbd0 demo.qcow2
>
> These don't do the same thing.  In fact the guestfish command
doesn't
> work at all.
>
> > I just want to mount demo.qcow2 to a device
>
> Still unclear.
>
> You want to export demo.qcow2 as NBD?  Use qemu-nbd.
>
> You want to mount demo.qcow2 on the local filesystem?  (This doesn't
> involve NBD.)  Use:
>
>   mkdir /tmp/mnt
>   guestmount --rw -a demo.qcow2 -i /tmp/mnt
>
> Rich.
>
> --
> Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~
> rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
> virt-df lists disk usage of guests without needing to install any
> software inside the virtual machine.  Supports Linux and Windows.
> http://people.redhat.com/~rjones/virt-df/

I tried this:
> mkdir /tmp/mnt
> guestmount --rw -a demo.qcow2 -i /tmp/mnt
but it shows guestmount no operating sys found on the disk
If using guestmount -i remove this option and choose the filesystems you
want to see by manually adding -m options

why