Re: [Qemu-discuss] QEMU with pre-created TAP in user mode

[Mike Lovell]

On 06/28/2012 08:05 AM, anatoly techtonik wrote:
> Hi,
>
> I've read that QEMU should work in user mode without sudo if TAP
> interface is pre-created. But I can not make it work. The interface is
> created with sudo:
>
> $ sudo tunctl
> Set 'tap0' persistent and owned by uid 0
> $ sudo ifconfig tap0 192.168.16.1/24
>
> But when I launch QEMU in user mode - it fails:
> $ qemu-kvm -hda linux.img -net user -net nic -net nic -net
> tap,ifname=tap0,script=no
> qemu-kvm: -net tap,ifname=tap0,script=no: could not configure
> /dev/net/tun (tap0): Operation not permitted
> qemu-kvm: -net tap,ifname=tap0,script=no: Device 'tap' could not be initialized
>
> Is that possible to run QEMU with TAP device to access guest from host
> without giving up admin rights?
> Did I miss something?

it is possible to do this and you are close. since you didn't specify a 
-u option to tunctl, the newly created tap device is only usable by 
root, or uid 0. try 'sudo tunctl -u <your username>' and then running 
qemu. this option to tunctl specifies which user has ownership of the 
tap device. you will also need to make sure that your user has the 
ability to read and write to /dev/net/tun.

mike