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

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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

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# brctl show bridge namebridge idSTP enabledinterfaces virbr08000.feffffffffffyesvif4.0

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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

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# 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