centos中lo是什么意思

在centOS7中，ifconfig命令已经被正式废除了，所以用该指令找不到网卡，我们在centOS中用ip addr来查看我们的网络信息。

In CentOS7, the ifconfig command has been officially revoked, so we can't find a web card with the command, and we use ip addr in the CentOS to view our network information.

lo是环回接口（loopback）。virbr是虚拟网桥（Virtual Bridge），virbr0是虚拟网桥网卡。一般centos6.5版本前普遍默认的网卡是eth0，centos7版本后普遍默认的网卡是ensxx（xx为数字）。当然也有已经修改过的网卡名称。环回接口的作用是作为本地软件环回测试本主机的进程之间的通信之用，简单理解，就是用做本机测试的，而且它的inet，也就是ip，只能是127.0.0.1。

Lo is the loopback interface (Loopback). Virbr is the virtual bridge, and virbr0 is the virtual network card. The popular default net card before version 6.5 of the general sendos is Eth0, the popular default net card after version 7 is the ensxx (xx is the number). There are, of course, modified netcard names. The ringback interface is used as a communication between the local software loop test host processes.

例如我的是centos7版本 默认网卡名称就是ens33，而centos6.5版本，默认网卡名称为eth0。

For example, I'm a "centos7" default card name is ens 33, while a "centos 6.5" default card name is eth0.

在虚拟机中，有些网卡名称是eth1或eth2，说明这个虚拟影像是被复制的，由于在物理机中的网卡eth0自动识别了物理机的MAC地址，在虚拟机中运行网卡名称就会自动变成eth1，如果复制这个虚拟影像在另一台电脑上运行，则网卡名称会变成eth2。但也可以修改ifcfg-eth0配置文件，绑定MAC地址，删除/etc/udev/rules.d/70-persistent-net.rules配置文件，重启生效。

In the virtual machine, some of the card names are eth1 or eth2, indicating that the virtual image is copied, and because the MAC address of the physics machine is automatically identified in the physics machine, the name of the net card running in the virtual machine automatically becomes eth1, and if the virtual image is copied and running on another computer, the card name becomes eth2. But it can also modify the iffg-eth0 configuration file, bind the MAC address, delete/etc/udev/rules.d/70-persistent-net.rules configuration file, and restart.

lo主要作用有两个：

L. has two main roles:

一是测试本机的网络配置，能PING通127.0.0.1说明本机的网卡和IP协议安装都没有问题；

One is to test the network configuration of the mainframe, which allows PING to pass 127.0.0.1 to explain that there are no problems with the network cards and IP protocol installation;

另一个作用是某些SERVER/CLIENT的应用程序在运行时需调用服务器上的资源

Another function is that some SERVER/CLIENT applications need to call resources on the server while they are running.