KVM 命令行安装虚拟机报错求救

环境：centos 6.3底层系统，安装了kvm组件
问题：用命令行安装虚拟机的时候报错，详情如下：
命令：[root@localhost ~]#virt-install --connect qemu:///system --name vm1 --ram 512 --vcpus=1 --disk path=/opt/mds/xuniji/vm1.img,size=50 --network bridge=br0 --os-type=linux --accelerate --cdrom=/root/CentOS-6.3-x86_64-bin-DVD2.iso --vnc
报错：Starting install...
ERROR internal error Process exited while reading console log output: char device redirected to /dev/pts/2
qemu-kvm: -drive file=/root/CentOS-6.3-x86_64-bin-DVD2.iso,if=none,media=cdrom,id=drive-ide0-1-0,readonly=on,format=raw: could not open disk image /root/CentOS-6.3-x86_64-bin-DVD2.iso: Permission denied

Domain installation does not appear to have been successful.
If it was, you can restart your domain by running:
virsh --connect qemu:///system start vm1
otherwise, please restart your installation.

看上去像是访问镜像的时候没有权限，但即使把镜像改成777权限依然报错。
请高手指点。。。。。。。。。。