KVM或Xen遇到Unable to retrieve http images/install.img

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/images/install.img

或者 Unable to retrieve http://mirrors.sohu.com/centos/6.5/os/x86_64/images/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

[images-x86_64]

initrd = images/pxeboot/initrd.img

kernel = isolinux/vmlinuz

[images-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