Re: [Qemu-devel] Re: Storing command line options in images

Jorge Lucángeli Obes
2007-08-11T01:41:41Z

> > My feeling is that config files are outdated. When used with a gui,
> > you end up writing silly parsers and stuff and still wrecking things
> > horribly when the the gui writer's expectations don't match reality.
> > When used without a gui, they increase the amount of details one has
> > to remember (where's that config file? I renamed my image, did I
> > remember to update the config file?). They also make upgrading more
> > difficult.
>
> There's only so much that can be expressed on a command line. There are
> actually limits to the command line size on a lot of platforms. I don't
> see why reading options from a file is so much worse than reading them
> from the command line.

In my view, the bottom line is: we need an _easy_ way of launching VMs
when one doesn't want all the options of the managed approach. I back
Avi on this one, I would like to be able to do

qemu guest.img

without worrying about configuration files, or XML, or parsing. That's
not to say that a global configuration file for QEMU wouldn't be
useful, but I think it would solve a different problem.

When I read Avi's TODO, I basically thought about getting rid of the
long command lines I had to store in scripts. I wanted to write that
command line once, and then forgetting about it, until I needed to
change it. I wanted an image to be self-contained as much as possible.
That's what I set to achieve.

All that said, I rethought Anthony's idea of storing plain text in the
image and with proper tools, it can work out. I don't like the idea of
having users overwriting and padding files, but the approach seems
less of a hack than using empty snapshots. In short: I think we will
need to have something like 'qemu-img cmdline' anyways, independent of
the implementation. That's because I would like an implementation that
does not depend on extra files. For that, we already have libvirt and
the likes.

Cheers,
Jorge