用virt-install安装kvm或xen，如果是用URL安装，会遇到这个问题：
Unable to retrieve http://192.168.22.242/p_w_picpaths/install.img
或者 Unable to retrieve http://mirrors.sohu.com/centos/6.5/os/x86_64/p_w_picpaths/install.img
解决方法
1，首先启动httpd服务，打开iptables的80端口，保证页面能访问
2，检查ip转发是否开启
cat /etc/sysctl.conf |grep ip_forward net.ipv4.ip_forward = 1 如果没有开启，则 vim /etc/sysctl.conf net.ipv4.ip_forward = 1 /sbin/sysctl -p
3,查看网络
是否没有配置br0，只是yum安装的
# brctl show bridge namebridge idSTP enabledinterfaces virbr08000.feffffffffffyesvif4.0
cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-br0 cat /etc/sysconfig/network-scripts/ifcfg-eth0 DEVICE=eth0 TYPE=Ethernet UUID=**** ONBOOT=yes NM_CONTROLLED=no BOOTPROTO=static BRIDGE=br0 DEFROUTE=yes IPV4_FAILURE_FATAL=yes IPV6INIT=no NAME="System eth0" HWADDR=**** cat /etc/sysconfig/network-scripts/ifcfg-br0 DEVICE=br0 TYPE=Bridge ONBOOT=yes NM_CONTROLLED=no BOOTPROTO=none IPADDR=**** PREFIX=** GATEWAY=**** DNS1=114.114.114.114 DOMAIN=114.114.114.114 DEFROUTE=yes NAME="System br0" service network restart
# brctl show bridge name bridge id STP enabled interfaces br 08000.0800278072e5 no eth0 virbr 08000.feffffffffff yes vif4.0
4，virt-install 后面接虚拟网卡的参数 -w bridge:br0
5,检查http挂载的iso目录.treeinfo
[p_w_picpaths-x86_64]
initrd = p_w_picpaths/pxeboot/initrd.img
kernel = isolinux/vmlinuz
[p_w_picpaths-xen]
kernel = isolinux/vmlinuz
initrd = isolinux/initrd.img
这样一通搞下来，应该没问题的，欢迎拍砖
