This is not helpful for you now, but you should look into etckeeper, it creates a git repo of your /etc directory, it hooks into APT and will create new commits when changes occur. It's not often that i use it, but it's reassuring to know that i have a history of the contents of /etc

With all networking problems it's a process of elimination, so you'll want to first figure out what problem you are facing.

• can you ping your local router? (maybe it's 192.168.1.1)
• can you ping the internet? (maybe try 8.8.8.8)

if those both work then you should move on to DNS, if they don't then you'll have to jump to trying to figure out what is wrong with your network devices

dns

To debug DNS issues, you can compare the output of running

getent hosts google.com

to something like

nslookup google.com 8.8.8.8

one will use an explicit DNS server (8.8.8.8) and the other is using the resolv conf configuration. if they both work and have somewhat similar output, then it's not DNS if the getent command fails, then you have a DNS issue.

If you have a problem with the contents of resolv conf, or it's not working, you'll first need to figure out which DNS configuration process you are using, it's probably either network manager, or systemd-resolved. I'm no expert in either, but once you know that you can start looking into how that system is configured.

networking

If it's not DNS then you need to figure out how your networking device is configured. Check that the networking systemd processes started is a good place to start, but you'll have to figure out what you are using for network configuration.

for server style /etc/network/interfaces configuration

sudo systemctl status networking.service

for network manager

sudo systemctl status NetworkManager.service