My debian cannot access the Internet. I know that (the interface is read-only and cannot be modified)

I cannot access the Internet In debian. I know (the interface is read-only and cannot be modified)-Linux general technology-Linux technology and application information. The following is a detailed description. I am sad. debian installed on the vm does not dare to directly run the tool on the computer. debian only has one installed user. The root password is unknown and I do not know how to modify it, the key issue is: I want to access the Internet. According to the method on the Internet, the vi/etc/network/interfaces file is in readonly mode and cannot be modified. What should I do, give me a method. I am sad.