Hi list,
I'm making a few modifications to the puppet-virt type from GitHub
(https://github.com/carlasouza/puppet-virt.git) and I've run across an
interesting problem with what looks like how a "command" in a Puppet
provider is escaping or interpreting it's arguments. Explaining this
is a bit long winded so bear with me...
We want to pass in multiple kernel boot arguments when doing a KVM
virt-install, a simple example is below. --extra-args takes a single
argument and can't be specified twice so if you want to specify
multiple you have to group them together as one string like so:
virt-install --name foo --extra-args "dhcp console=ttyS0 ks=http://
ks/foo.ks"
This gets translated by virt-install (Python) into individual
arguments after "-append" to the qemu-kvm binary like so:
/usr/bin/qemu-kvm <heaps of other arguments> -append method=http://
gs2repo.gs2.tradefair/mrepo/latest/fedora15-x86_64/RPMS.os/ noipv6
console=ttyS0,115200 dhcp ks=http://gs2repo.gs2.tradefair/mrepo/
kickstarts/fedora15.ks
So the transition of arguments is "Shell -> Python -> Binary" and
everything works grand. Now, trying to replicate the same thing in
Puppet has proved difficult. Nearest I can tell with my limited
Puppet / Ruby knowledge, the argument list is being handled
differently and so what gets put on the qemu-kvm binary's command line
is one single string of arguments that aren't expanded out properly
and so qemu-kvm doesn't function as we intend.
Here's how I'm trying to do it in Puppet. A simplified virt resource
in a manifest, note the double sets of quotes:
virt { "foo":
ensure => running,
boot_options => '"noipv6 console=ttyS0,115200 dhcp ks=http://
gs2repo.gs2.tradefair/mrepo/kickstarts/fedora15.ks"',
}
This gets translated into the provider (heavily simplified below for
brevity), arguments are pulled from resource parameters and translated
into arrays and appended as arguments to the Puppet/Ruby virt-install
command:
Puppet::Type.type(:virt).provide(:libvirt) do
commands :virtinstall => "/usr/bin/virt-install"
bootargs = ["--extra-args", resource[:boot_options] ]
def install
virtinstall generalargs + networkargs + graphicargs +
bootargs
Applying this manifest and looking at the debug output, it seems to be
escaped correctly:
debug: Puppet::Type::Virt::ProviderLibvirt: Executing '/usr/bin/
virt-install --name foo --extra-args "dhcp console=ttyS0 ks=http://ks/
foo.ks"'
notice: /Stage[main]//Virt[foo]/ensure: created
However if you then check to see what qemu-kvm command is now running,
it's still got the shell quotes in the argument list:
/usr/bin/qemu-kvm <heaps of other arguments> -append method=http://
gs2repo.gs2.tradefair/mrepo/latest/fedora15-x86_64/RPMS.os/ "noipv6
console=ttyS0,115200 dhcp ks=http://gs2repo.gs2.tradefair/mrepo/
kickstarts/fedora15.ks"
This causes some strange side affects, like the machine kickstarting
but no console, or if you reorder things, you can get a console but
the kickstart isn't found. Single quotes vs double quotes isn't much
better, qemu-kvm just behaves different but still incorrect. I've
tried passing the arguments as an array from Puppet/Ruby, but this
won't work as virt-install must take a single multi-word string as the
one and only argument to --extra-args or it complains. You could argue
that virt-install could be more helpful and accept multiple --extra-
args, but it's the only tool at hand.
So, somewhere between Puppet/Ruby and Python the arguments are being
passed to virt-install strangely, maybe the way Puppet exec's it's
commands? I'm not sure.
For the moment I've managed to work around this using a dirty, dirty
hack:
commands :virtinstall => "/bin/sh"
virtinstallargs = generalargs + networkargs + graphicargs +
bootargs
virtinstallstring = "/usr/bin/virt-install " +
virtinstallargs.join(' ')
virtinstall [ "-c", virtinstallstring ]
I'd like to be able to do it without using a shell to get the desired
escaping behaviour.
It's a bit of a strange one, but if anyone has any suggestions I could
try I'll give them a go.
Thanks,
-Luke
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