Hello,
spawn qemu-system-x86_64 -no-kvm -cpu core2duo -m 256 -serial mon:stdio -cdrom var/run/demo.iso qemu-system-x86_64: -no-kvm: invalid option ...
I'm currently running centos 6 as a remote server and doing the builds there and initially I didn't have qemu-system available on it. It took me a while to locate an rpm (in rpmforge-extras) that had qemu-system_x86_64 - however it does not recognise the -no-kvm command line option.
you just hit a pretty inconvenient inconsistency regarding the naming of Qemu or respectively KVM as shipped on different Linux distributions. On Ubuntu, the executable that is called qemu is actually KVM. Because KVM has known problems with handling most of the microkernels used by Genode, we supply this option to explicitly disable KVM. Apparently, your distribution seems to actually ship a Qemu binary named qemu. Qemu, however, does not know about such an option.
You can prevent the Genode tools from passing this argument to qemu by editing the '<build-dir>/etc/build.conf' file. Please remove the following line:
QEMU_OPT += -no-kvm
You are actually not the first one stumbling over this issue. There is a discussion (but no conclusion) about possible improvements here:
https://github.com/genodelabs/genode/issues/500
Using Ubuntu as a Genode development environment is certainly the easiest way to avoid problems like that because most of the regular Genode developers use some flavor of Debian or Ubuntu. So you would walk on tested ground. Personally, I use the minimal install version of Ubuntu (the one that comes without an X server) and just installed a few additional packages (such as Xorg and a plain window manager, but no desktop environment).
Cheers Norman