首先安装好系统CentOS系统，宿主机只安装base的基本包，然后用yum安装常见的xen,kernel-xen软件。
2.xen软件安装好之后检查一下/etc/grub.conf文件设置启动选项为后缀为xen 的内核，最后reboot重新启动。
3.系统启动好之后查看宿主机信息
[root@localhost ~]# xm li //xm list显示domain 0的信息。
Name ID Mem(MiB) VCPUs State Time(s)
Domain-0 0 282 1 r----- 804.7
4.ifconfig -a查看桥和虚拟网卡
xen的网络桥接模式的工作流程，现翻译在下面以备后面之需。
When xend is started, with the default configuration (in /etc/xen/xend-config.sxp), it'll execute /etc/xen/scripts/network-bridge to re-configure your networking.
当xend这个进程被开启之后，进程会根据默认的配置文件/etc/xen/xend-config.sxp里的内容，让/etc/xen/scripts/network-bridge这个脚本发挥工作，重新来配置你的网络。
It'll rename the physical eth0 interface to peth0, change it's MAC address to FE:FF:FF:FF:FF:FF, and then create a virtual ethernet interface called eth0, configure it with the real MAC address, and bridge both of those interfaces to xenbr0 bridge.
它会将你的eth0重命名为peth0，把eth0的MAC值改为FE:FF:FF:FF:FF:FF。然后再重新创建一个虚拟的网络接口，将它命名为eth0，配置它让它有物理上的MAC地址，然后把peth0跟eth0这两个接口跟xenbr0做一个桥接。
This way the virtual eth0 interface should have a real MAC, and it can be used for dom0 management, and at the same time allow other VMs/domUs to share the physical ethernet interface by using xenbr0 bridge.
所以说，按这种方式虚拟出来的eth0这个接口会有物理上的MAC值，在domain0中发挥上网的功用，同时它也允许domainU通过xenbr0这个桥接接口跟domain0合用物理网络接口。
[root@localhost ~]# brctl show
bridge name bridge id STP enabled interfaces
virbr0 8000.000000000000 yes
xenbr0 8000.feffffffffff no vif3.0
vif0.0
peth0
[root@localhost ~]# ifconfig -a
eth0 Link encap:Ethernet HWaddr 00:0C:29:15:56:F2
inet addr:192.168.40.232 Bcast:192.168.40.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:45498 errors:0 dropped:0 overruns:0 frame:0
TX packets:13674 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:19669317 (18.7 MiB) TX bytes:1924647 (1.8 MiB)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:2 errors:0 dropped:0 overruns:0 frame:0
TX packets:2 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:100 (100.0 b) TX bytes:100 (100.0 b)
peth0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF
UP BROADCAST RUNNING NOARP MTU:1500 Metric:1
RX packets:324838 errors:2 dropped:2 overruns:0 frame:0
TX packets:118994 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:402460402 (383.8 MiB) TX bytes:9313197 (8.8 MiB)
Interrupt:18 Base address:0x2000
veth1 Link encap:Ethernet HWaddr 00:00:00:00:00:00
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
veth2 Link encap:Ethernet HWaddr 00:00:00:00:00:00
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
veth3 Link encap:Ethernet HWaddr 00:00:00:00:00:00
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
vif0.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF
UP BROADCAST RUNNING NOARP MTU:1500 Metric:1
RX packets:13719 errors:0 dropped:0 overruns:0 frame:0
TX packets:45546 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1931157 (1.8 MiB) TX bytes:19672872 (18.7 MiB)
vif0.1 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
vif0.2 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
vif0.3 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
vif3.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF
UP BROADCAST RUNNING NOARP MTU:1500 Metric:1
RX packets:314 errors:0 dropped:0 overruns:0 frame:0
TX packets:1649 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:500
RX bytes:23922 (23.3 KiB) TX bytes:434040 (423.8 KiB)
virbr0 Link encap:Ethernet HWaddr 00:00:00:00:00:00
inet addr:192.168.122.1 Bcast:192.168.122.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:14 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:3137 (3.0 KiB)
xenbr0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF
UP BROADCAST RUNNING NOARP MTU:1500 Metric:1
RX packets:26586 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:6736372 (6.4 MiB) TX bytes:0 (0.0 b)