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问题：centos7开机出现问题无法连接网络，之前正常。

执行 ifconfig 显示没有ens33网卡，但是同样的其他虚拟机却是正常状态：

[root@hadoop108 ~]# ifconfig
lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 11496  bytes 900336 (879.2 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 11496  bytes 900336 (879.2 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

virbr0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        inet 192.168.122.1  netmask 255.255.255.0  broadcast 192.168.122.255
        ether 52:54:00:71:26:9e  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

查看ip link

[root@hadoop108 ~]# ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: ens33: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 00:0c:29:f2:ae:65 brd ff:ff:ff:ff:ff:ff
3: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN mode DEFAULT group default qlen 1000
    link/ether 52:54:00:71:26:9e brd ff:ff:ff:ff:ff:ff
4: virbr0-nic: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast master virbr0 state DOWN mode DEFAULT group default qlen 1000
    link/ether 52:54:00:71:26:9e brd ff:ff:ff:ff:ff:ff

显示ens33网卡为DOWN状态，

查看网络状态：

[root@hadoop108 ~]# systemctl status network.service
● network.service - LSB: Bring up/down networking
Loaded: loaded (/etc/rc.d/init.d/network; bad; vendor preset: disabled)
Active: failed (Result: exit-code) since 三 2023-05-24 09:16:00 CST; 31s ago
Docs: man:systemd-sysv-generator(8)
Process: 9720 ExecStart=/etc/rc.d/init.d/network start (code=exited, status=1/FAILURE)

5月 24 09:16:00 hadoop108 network[9720]: RTNETLINK answers: File exists
5月 24 09:16:00 hadoop108 network[9720]: RTNETLINK answers: File exists
5月 24 09:16:00 hadoop108 network[9720]: RTNETLINK answers: File exists
5月 24 09:16:00 hadoop108 network[9720]: RTNETLINK answers: File exists
5月 24 09:16:00 hadoop108 network[9720]: RTNETLINK answers: File exists
5月 24 09:16:00 hadoop108 network[9720]: RTNETLINK answers: File exists
5月 24 09:16:00 hadoop108 systemd[1]: network.service: control process exited, code=exited status=1
5月 24 09:16:00 hadoop108 systemd[1]: Failed to start LSB: Bring up/down networking.
5月 24 09:16:00 hadoop108 systemd[1]: Unit network.service entered failed state.
5月 24 09:16:00 hadoop108 systemd[1]: network.service failed.

 重启网卡

[root@hadoop108 ~]# systemctl restart network
Job for network.service failed because the control process exited with error code. See "systemctl status network.service" and "journalctl -xe" for details.
[root@hadoop108 ~]# journalctl -xe
5月 24 09:41:01 hadoop108 NetworkManager[685]: <info>  [1684892461.3726] audit: op="con
5月 24 09:41:01 hadoop108 network[5872]: 正在打开接口 ens33： 错误：连接激活失败：No su
5月 24 09:41:01 hadoop108 network[5872]: [失败]
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 systemd[1]: network.service: control process exited, code=exi
5月 24 09:41:01 hadoop108 systemd[1]: Failed to start LSB: Bring up/down networking.
-- Subject: Unit network.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- Unit network.service has failed.
-- 
-- The result is failed.
5月 24 09:41:01 hadoop108 systemd[1]: Unit network.service entered failed state.
5月 24 09:41:01 hadoop108 systemd[1]: network.service failed.
5月 24 09:41:01 hadoop108 polkitd[616]: Unregistered Authentication Agent for unix-proc

查看日志：

5月 24 09:41:01 hadoop108 NetworkManager[685]: <info>  [1684892461.3726] audit: op="connection-activate" uuid="b90d3d59-d742-45b5-ba56-f5b47644b948" name="ens33" result="fail" reason="No suitable device found fo
5月 24 09:41:01 hadoop108 network[5872]: 正在打开接口 ens33： 错误：连接激活失败：No suitable device found for this connection (device lo not available because device is strictly unmanaged).
5月 24 09:41:01 hadoop108 network[5872]: [失败]
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 network[5872]: RTNETLINK answers: File exists
5月 24 09:41:01 hadoop108 systemd[1]: network.service: control process exited, code=exited status=1
5月 24 09:41:01 hadoop108 systemd[1]: Failed to start LSB: Bring up/down networking.
-- Subject: Unit network.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- Unit network.service has failed.
-- 
-- The result is failed.
5月 24 09:41:01 hadoop108 systemd[1]: Unit network.service entered failed state.
5月 24 09:41:01 hadoop108 systemd[1]: network.service failed.
5月 24 09:41:01 hadoop108 polkitd[616]: Unregistered Authentication Agent for unix-process:5866:54555 (system bus name :1.120, object path /org/freedesktop/PolicyKit1/AuthenticationAgent, locale zh_CN.UTF-8) (di
~
~

 尝试启动ens33网络接口失败：

[root@hadoop108 ~]# ifup ens33
错误：连接激活失败：No suitable device found for this connection (device lo not available because device is strictly unmanaged).

问题总结：vm虚拟机下其他centos7是正常的，单台centos7网络异常，不是由于windows中VMware net相关服务导致的，是单台centos7的问题导致。确保配置文件(/etc/sysconfig/network-scripts/ifcfg-ens33)正常的情况下，可以尝试以下方法：

1. 将NetworkManager服务从系统启动时的运行级别中移除，以防止它在系统启动时自动运行，手动配置网络连接

   [root@hadoop108 ~]# chkconfig NetworkManager off
   注意：正在将请求转发到“systemctl disable NetworkManager.service”。
   Removed symlink /etc/systemd/system/multi-user.target.wants/NetworkManager.service.
   Removed symlink /etc/systemd/system/dbus-org.freedesktop.nm-dispatcher.service.
   Removed symlink /etc/systemd/system/network-online.target.wants/NetworkManager-wait-online.service.
   

2. 将network服务在系统启动时自动运行

   [root@hadoop108 ~]# chkconfig network on

3. 停止正在运行的NetworkManager服务

   [root@hadoop108 ~]# service NetworkManager stop
   Redirecting to /bin/systemctl stop NetworkManager.service
   

4. 启动network服务

   [root@hadoop108 ~]# service network start
   Starting network (via systemctl):                          [  确定  ]

5. 测试网络连接正常

   [root@hadoop108 ~]# ifconfig | grep ens33
   ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
   [root@hadoop108 ~]# ping www.baidu.com -c 3
   PING www.a.shifen.com (110.242.68.3) 56(84) bytes of data.
   64 bytes from 110.242.68.3 (110.242.68.3): icmp_seq=1 ttl=128 time=53.6 ms
   64 bytes from 110.242.68.3 (110.242.68.3): icmp_seq=2 ttl=128 time=53.6 ms
   64 bytes from 110.242.68.3 (110.242.68.3): icmp_seq=3 ttl=128 time=53.2 ms
   
   --- www.a.shifen.com ping statistics ---
   3 packets transmitted, 3 received, 0% packet loss, time 3124ms
   rtt min/avg/max/mdev = 53.200/53.494/53.675/0.282 ms