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[Libguestfs] Re: libguestfs performance



On Mon, Dec 07, 2009 at 03:33:41PM +0100, Pierre Riteau wrote:
> This is much better (on my test system it writes at about 15 MB/s).
> However, it is still far from what the hardware can do (more than 60 MB/s).

It'd be interesting to know whether the problem is with reading from
the ISO image, or with writing to the disk, or with all the processing
that tar and the virtual kernel is doing.  Tricky to measure that
though ...

> Now the last problem is that I need to install a bootloader. Can I
> easily install grub in the appliance, or do I need to recreate a new
> one?

You should be able to issue the grub-install command:

  http://libguestfs.org/guestfish.1.html#grub_install

IIRC the syntax is something like:

  grub-install /boot hd0

> > However we found experimentally that the fastest method of all for
> > creating distributions was to prebuild an ext2/3/4 image, and 'dd' it
> > over to the target partition, then resize it to the final (larger)
> > size.  This method is extremely quick, enabling us to build Fedora
> > images in just a minute or two:
> > 
> > http://rwmj.wordpress.com/2009/11/23/prebuilt-distributions-part-2/#content
> 
> I've read your blog, this is interesting. I will see how I can leverage that.

I'm pretty certain this is the way to go.  Note that the 'dd' command
hasn't made it into a released version of libguestfs.  It was added in
this commit, just after 1.0.79 was released:

http://git.annexia.org/?p=libguestfs.git;a=commit;h=22e531bc459309d9a871a845cfacd1396ff5b7e4

Rich.

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


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