[libvirt-users] Error in launching chasis

Laine Stump laine at redhat.com
Tue Dec 17 17:15:04 UTC 2019

On 12/17/19 5:52 AM, abhishek jain wrote:
> Hi
> I am new to Libvirt and is starting Chassis but getting following error
> qemu-system-x86_64: -netdev 
> tap,id=net0,ifname=tap01,vhost=on,script=no,downscript=no: tap: open 
> vhost char device failed: Operation not permitted

You aren't using libvirt, you are running the qemu-system-x86_64 command 

> What could be the reason

Since you're not actually using libvirt in this example, this isn't the 
best place to ask, but based on the error message, I'd say that you are 
running qemu-system-x86_64 as an unprivileged user, and qemu is trying 
to open the device /dev/vhost-net, but can't due to the lack of privileges.

If you used a libvirt-based management application to start your qemu 
(e.g. virsh, virt-manager, cockpit, ovirt, openstack) then they would 
call the libvirtd daemon, which is running with full root privileges and 
would open the vhost-net device, then pass that to an unprivileged qemu. 
If you really must continue using qemu directly, then you'll need to 
either stop using vhost=on, or run qemu as root (and take all the 
security risks associated with that).

> Regards
> Abhishek
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