When passing kernel command line arguments, it is possible to have spaces. The arguments should be protected in qoutes. In http://libvirt.org/formatdomain.html "direct kernel boot" section, there is an example. ... <os> <type>hvm</type> <loader>/usr/lib/xen/boot/hvmloader</loader> <kernel>/root/f8-i386-vmlinuz</kernel> <initrd>/root/f8-i386-initrd</initrd> <cmdline>console=ttyS0 ks=http://example.com/f8-i386/os/</cmdline> </os> ... If the contents in <cmdline> are passed as-is to qemu, then qemu will see qemu ... -append console=ttyS0 ks=http://example.com/f8-i386/os/ ... It must be quoted, so let qemu see qemu ... -append "console=ttyS0 ks=http://example.com/f8-i386/os/" ... Signed-off-by: Zhou Zheng Sheng <zhshzhou@linux.vnet.ibm.com> --- src/qemu/qemu_command.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)