systemctl restart network.service命令执行失败
今天拷贝了一个linux虚拟机，要修改虚拟机ip和计算机名。先修改ip地址：
[root@centos ~]# vim /etc/sysconfig/network-scripts/ifcfg-eno16777736
改了地址之后，重启网络服务，执行命令，报错如下：
Job for network.service failed because the control process exited with error code. See "systemctl status network.service" and "journalctl -xe" for details.
[root@centos ~]# systemctl status network.service
● network.service - LSB: Bring up/down networking
Loaded: loaded (/etc/rc.d/init.d/network)
Active: failed (Result: exit-code) since Tue 2019-12-10 22:12:47 PST; 14s ago
Docs: man:systemd-sysv-generator(8)
Process: 3828 ExecStop=/etc/rc.d/init.d/network stop (code=exited, status=0/SUCCESS)
Process: 4348 ExecStart=/etc/rc.d/init.d/network start (code=exited, status=1/FAILURE)
Dec 10 22:12:47 centos network[4348]: RTNETLINK answers: File exists
Dec 10 22:12:47 centos network[4348]: RTNETLINK answers: File exists
Dec 10 22:12:47 centos network[4348]: RTNETLINK answers: File exists
Dec 10 22:12:47 centos network[4348]: RTNETLINK answers: File exists
Dec 10 22:12:47 centos network[4348]: RTNETLINK answers: File exists
Dec 10 22:12:47 centos network[4348]: RTNETLINK answers: File exists
Dec 10 22:12:47 centos systemd[1]: network.service: control process exited,...=1
Dec 10 22:12:47 centos systemd[1]: Failed to start LSB: Bring up/down netwo...g.
Dec 10 22:12:47 centos systemd[1]: Unit network.service entered failed state.
Dec 10 22:12:47 centos systemd[1]: network.service failed.
Hint: Some lines were ellipsized, use -l to show in full.
带上-l参数查看详细错误：
[root@centos ~]# systemctl status network.service -l
● network.service - LSB: Bring up/down networking
Loaded: loaded (/etc/rc.d/init.d/network)
Active: failed (Result: exit-code) since Tue 2019-12-10 22:12:47 PST; 52s ago
Docs: man:systemd-sysv-generator(8)
Process: 3828 ExecStop=/etc/rc.d/init.d/network stop (code=exited, status=0/SUCCESS)
Process: 4348 ExecStart=/etc/rc.d/init.d/network start (code=exited, status=1/FAILURE)
Dec 10 22:12:47 centos network[4348]: RTNETLINK answers: File exists
Dec 10 22:12:47 centos network[4348]: RTNETLINK answers: File exists
Dec 10 22:12:47 centos network[4348]: RTNETLINK answers: File exists
Dec 10 22:12:47 centos network[4348]: RTNETLINK answers: File exists
Dec 10 22:12:47 centos network[4348]: RTNETLINK answers: File exists
Dec 10 22:12:47 centos network[4348]: RTNETLINK answers: File exists
Dec 10 22:12:47 centos systemd[1]: network.service: control process exited, code=exited status=1
Dec 10 22:12:47 centos systemd[1]: Failed to start LSB: Bring up/down networking.
Dec 10 22:12:47 centos systemd[1]: Unit network.service entered failed state.
Dec 10 22:12:47 centos systemd[1]: network.service failed.
重点查了一下这个错误：Failed to start LSB: Bring up/down networking. 原来虚拟机复制之后要修改mac地址，把虚拟机本身的mac地址得修改到ifcfg-eno16777736文件的HWADDR参数中。
查看mac地址：
[root@centos ~]# ip addr
1: lo:
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eno16777736:
link/ether 00:0c:29:6a:73:c4 brd ff:ff:ff:ff:ff:ff
3: virbr0:
link/ether 52:54:00:26:03:f7 brd ff:ff:ff:ff:ff:ff
inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0
valid_lft forever preferred_lft forever
4: virbr0-nic:
link/ether 52:54:00:26:03:f7 brd ff:ff:ff:ff:ff:ff
蓝色字体的部分是mac地址，复制到ifcfg-eno16777736文件的HWADDR参数中，如果没有这个参数就新建一个。
[root@centos ~]# vim /etc/sysconfig/network-scripts/ifcfg-eno16777736
[root@centos ~]# systemctl restart network.service
[root@centos ~]#
重启正常。
---------------------
今天打开虚拟机，网络突然连不上了，一看上面网卡的设置，里面HWADDR参数没有了，又重新加了一下，然后再启动network服务，结果又报上面的错，network.service - LSB: Bring up/down networking。
后来查看具体日志：journalctl -xe
看到日志里写：Bringing up interface eno16777736: Error: Connection activation failed
查了一下说是Netmanager服务和网卡配置不一致引起的，需要把netmanager服务停止了。
解决方法
systemctl stop NetworkManager.service
systemctl disable NetworkManager.service
systemctl restart Network.service
OK，可以连上虚拟机了。