problem analysis
When using a virtual machine, you may not be able to connect to the network every time you shut down and restart, but if the system settings are all right, you can try to restart the network.
Solution
Open the terminal command line, type the following command, and you should be able to surf the Internet.
/etc/init.d/networking restart
If the above method does not help, try typing the following command.
/etc/init.d/network-manager restart