CentOS7.7 系统下 virbr0 虚拟网卡的维护与管理

       在 CentOS 7 系统的安装过程中，如果有选择相关虚拟化的的服务安装系统后，启动网卡时会发现有一个以网桥连接的私网地址的 virbr0 网卡，这个是因为在虚拟化中有使用到 libvirtd 服务生成的，如果不需要可以关闭后去掉：

一、查看IP及网桥设备

查看系统版本：

[root@node ~]# cat /etc/redhat-release 
CentOS Linux release 7.7.1908 (Core)

查看IP地址：

[root@node ~]# ip -4 addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    inet 192.168.51.103/24 brd 192.168.51.255 scope global noprefixroute dynamic ens33
       valid_lft 5089sec preferred_lft 5089sec
3: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
    inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0
       valid_lft forever preferred_lft forever

查看网桥信息：

[root@node ~]# brctl show
bridge name    bridge id            STP enabled    interfaces
virbr0         8000.525400f9f9fe    yes            virbr0-nic

二、使用 brctl 命令管理网桥

brctl 命令的帮助信息：

[root@node ~]# brctl
Usage: brctl [commands]
commands:
    addbr         <bridge>                  add bridge     //增加网桥
    delbr         <bridge>                  delete bridge  //删除网桥
    addif         <bridge> <device>         add interface to bridge
    delif         <bridge> <device>         delete interface from bridge
    hairpin       <bridge> <port> {on|off}  turn hairpin on/off
    setageing     <bridge> <time>           set ageing time
    setbridgeprio <bridge> <prio>           set bridge priority
    setfd         <bridge> <time>           set bridge forward delay
    sethello      <bridge> <time>           set hello time
    setmaxage     <bridge> <time>           set max message age
    setpathcost   <bridge> <port> <cost>    set path cost
    setportprio   <bridge> <port> <prio>    set port priority
    show          <bridge> ]                show a list of bridges
    showmacs      <bridge>                  show a list of mac addrs
    showstp       <bridge>                  show bridge stp info
    stp           <bridge> {on|off}         turn stp on/off

删除网桥：

[root@node ~]# ifconfig virbr0 down
[root@node ~]# brctl delbr virbr0

三、禁用开机自启动 libvirtd 服务

[root@node ~]# systemctl disable libvirtd.service    # 禁用libvirtd 服务开机自启动
Removed symlink /etc/systemd/system/multi-user.target.wants/libvirtd.service.
Removed symlink /etc/systemd/system/sockets.target.wants/virtlogd.socket.
Removed symlink /etc/systemd/system/sockets.target.wants/virtlockd.socket.
[root@node ~]# systemctl  status libvirtd.service
● libvirtd.service - Virtualization daemon
   Loaded: loaded (/usr/lib/systemd/system/libvirtd.service; disabled; vendor preset: enabled)
   Active: inactive (dead) since Sun 2019-12-15 13:31:13 CST; 42min ago
     Docs: man:libvirtd(8)
           https://libvirt.org
 Main PID: 1193 (code=exited, status=0/SUCCESS)
   CGroup: /system.slice/libvirtd.service
           ├─1822 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/default.conf --leasefile-ro --dhcp-script=/usr/libexec/libvirt_leaseshelper
           └─1823 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/default.conf --leasefile-ro --dhcp-script=/usr/libexec/libvirt_leaseshelper

Dec 15 11:43:15 node dnsmasq-dhcp[1822]: DHCP, sockets bound exclusively to interface virbr0
Dec 15 11:43:15 node dnsmasq[1822]: no servers found in /etc/resolv.conf, will retry
Dec 15 11:43:15 node dnsmasq[1822]: read /etc/hosts - 2 addresses
Dec 15 11:43:15 node dnsmasq[1822]: read /var/lib/libvirt/dnsmasq/default.addnhosts - 0 addresses
Dec 15 11:43:15 node dnsmasq-dhcp[1822]: read /var/lib/libvirt/dnsmasq/default.hostsfile
Dec 15 13:30:01 node dnsmasq[1822]: reading /etc/resolv.conf
Dec 15 13:30:01 node dnsmasq[1822]: using nameserver 192.168.1.1#53
Dec 15 13:30:01 node dnsmasq[1822]: using nameserver 192.168.51.1#53
Dec 15 13:31:13 node systemd[1]: Stopping Virtualization daemon...
Dec 15 13:31:13 node systemd[1]: Stopped Virtualization daemon.
[root@node ~]# systemctl mask libvirtd.service
Created symlink from /etc/systemd/system/libvirtd.service to /dev/null.

四、验证

[root@node ~]# ip -4 add
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    inet 192.168.51.103/24 brd 192.168.51.255 scope global noprefixroute dynamic ens33
       valid_lft 4464sec preferred_lft 4464sec

    结果发现：virbr0 已被删除。