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[Qemu-devel] Writing a C library to generate qemu command lines and conf
From: |
Richard W.M. Jones |
Subject: |
[Qemu-devel] Writing a C library to generate qemu command lines and configuration files |
Date: |
Tue, 2 May 2017 09:35:00 +0100 |
User-agent: |
Mutt/1.5.20 (2009-12-10) |
Firstly, is there such a thing already? (libvirt doesn't count since
it cannot generate -readconfig configuration files)
Well, I have written one. It's in C and doesn't have any dependencies
beyond the standard C library:
https://github.com/rwmjones/libguestfs/tree/max-disks/common/qemuopts
It models command line parameters as either flags (eg. ‘-nodefconfig’),
flags with a single argument (‘-name guest’), or flags taking a list
(eg. ‘-drive file=foo,id=bar’ modeled as a list of strings).
I'm immediately aware that there are shortcomings with this approach
(see below). Is there a better model to use for qemu command line
options that also allows -readconfig config files to be generated?
Some of the more obvious problems:
* I don't know if single flags can be translated into config files.
* Config files treat the "id=.." parameter as special, eg:
‘-drive file=foo,id=bar’ is translated to:
[drive "bar"]
file = "foo"
* There's no clear mapping between some command line parameters and
the config file, eg. ‘-m 2048 -kernel foo’ should be translated into:
[memory]
size = "2048"
[machine]
kernel = "foo"
but my library couldn't do that translation without a look-up table
that would duplicate the internals of qemu.
There are also unknown unknowns:
* Is comma-quoting (ie. doubling any commas) sufficient? Or are there
other forms of quoting? A quick look at options parsing in qemu
doesn't show any.
* From the point of view of a client generating command lines, is there
any significance to dotted names (eg. ‘-drive file.driver=ssh,...’)
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-p2v converts physical machines to virtual machines. Boot with a
live CD or over the network (PXE) and turn machines into KVM guests.
http://libguestfs.org/virt-v2v
- [Qemu-devel] Writing a C library to generate qemu command lines and configuration files,
Richard W.M. Jones <=