[CentOS] qemu-system-x86_64 does not support fw_cfg option

Wed Jul 26 11:31:51 UTC 2017
Steve Rubie-Todd <steve at rubie-todd.com>

On 26/07/2017 11:44, Gianluca Cecchi wrote:
> On Wed, Jul 26, 2017 at 12:20 PM, Steve Rubie-Todd <steve at rubie-todd.com>
> wrote:
>
>> Hi
>>
>> I am trying to run CoreOS (Container Linux) as a guest OS using KVM/QEMU.
>> One of their suggestions is to pass config info into the VM using the
>> "fw_cfg" option . When I try this I get the error "-fw_cfg invalid option".
>> If I run the vm with the help option it does not list the fw_cfg option.
>> However, according to the qemu documentation, see here <
>> https://qemu.weilnetz.de/doc/qemu-doc.html#Debug_002fExpert-options>,
>> they support this option.
>>
>> The command used to run the vm is:
>>
>>     /usr/bin/qemu-system-x86_64 -name CL-IGN-1 -m 1024 \
>>          -net nic,vlan=0,model=virtio \
>>          -net user,vlan=0,hostfwd=tcp::2222-:22,hostname=CL-IGN-1 \
>>          -drive if=virtio,file=./coreos_production_qemu_image.img \
>>          -fw_cfg name=opt/com.coreos/config,file=./CL-IGN-1.ignconfig
>>
>>     qemu-system-x86_64: -fw_cfg: invalid option
>>
>> I also tried using /usr/libexec/qemu-kvm but got the same error.
>>
>> I am running::
>>
>>     CentOS Linux release 7.3.1611 (Core)
>>
>>     qemu-system-x86-2.0.0-1.el7.6.x86_64
>>     qemu-kvm-1.5.3-126.el7.x86_64
>>
>>
>> Thanks.
>>
> Hello,
> I think (based also on your qemu-kvm version man page), that the feature is
> not present in qemu-kvm version provided by base CentOS.
> But you can use packages provided by the Virtualization SIG
> Good idea especially if virtualization is core service for your server.
> See here the announcement:
> https://lists.centos.org/pipermail/centos-announce/2015-October/021445.html
>
> So you can follow what detailed there:
> yum install centos-release-qemu-ev
> yum install qemu-kvm-ev
>
> I reproduced a situation on a CentOS 7.3 server where qemu-kvm is already
> present and you can do
>
> yum install centos-release-qemu-ev
>
> and then
>
> yum update qemu-kvm-ev
> ...
> Dependencies Resolved
>
> ====================================================================================================
>   Package                   Arch          Version
>   Repository             Size
> ====================================================================================================
> Installing:
>   qemu-img-ev               x86_64        10:2.6.0-28.el7.10.1
> centos-qemu-ev        1.0 M
>       replacing  qemu-img.x86_64 10:1.5.3-126.el7_3.10
>   qemu-kvm-common-ev        x86_64        10:2.6.0-28.el7.10.1
> centos-qemu-ev        516 k
>       replacing  qemu-kvm-common.x86_64 10:1.5.3-126.el7_3.10
>   qemu-kvm-ev               x86_64        10:2.6.0-28.el7.10.1
> centos-qemu-ev        2.5 M
>       replacing  qemu-kvm.x86_64 10:1.5.3-126.el7_3.10
>
> Transaction Summary
> ====================================================================================================
> Install  3 Packages
>
> so it seems it automatically obsoletes the "standard" packages, because
> they overlap in filesand you can have only one installed
>
> And now you should have the -fw_cfg option.
>
> BTW: the version of the hypervisor used by Virtualization SIG is the same
> used by the Virtualization Platform project named oVirt (
> http://www.ovirt.org), upstream for commercial RHEV solution, so rock
> solid, I'm currently using it extensively ;-)
>
> HIH,
> Gianluca
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>
Many thanks for your quick response Gianluca. I installed the "ev" 
packages and now I can pass the "fw_cfg" option to the vm.

Regards

Steve.