Ubuntu 20.04 temporary failure in name resolution for wired

Question

I am getting the following error from ubuntu 20.04 terminal, connected via wired ethernet connection: When I type the following command which I am using in a bash script:

ping -c 1 google.com

for a health check to ensure it has access, I get the following error:

ping: google.com: Temporary failure in name resolution

Some background

I overwrote my older gaming rig to be a ubuntu multi purpose server (including smart home automation) in my home network. It used to be windows 10, but I formatted the drive and installed ubuntu on it.

I have not yet been able to access the internet with ubuntu, however, I do know that the equipment works because I left the internet wired in, I actually downloaded ubuntu via that machine onto the usb before installing.

Now I cannot see or connect to the ubuntu server from other devices and cannot reach the internet to download even basic tools like netstat.

At this point, I feel like I've bashed my head against a wall and scoured the internet (and lots of other stack overflow threads) and tried a bunch of things that didn't work.

Any help would be greatly appreciated!

Edit: As requested in comments, I am attaching a screenshot, since I am not able access the computer via any network. Only via hdmi.

Edit 2: Second screenshot as requested.

Answer 1

It's likely your default DNS server is pointing to an IP address that is not capable of resolving DNS queries. You should check the DNS settings in the file that /etc/resolv.conf is pointing to. When you go to that file (/var/run/systemd/resolve/resolve.conf), look at the IP that is right next to the keyword namespace. You should set it to your router's IP address (which can be found with the command route -n. Look for the gateway column and take the one that's not 0.0.0.0) or you can also set it to a public DNS server such as 1.1.1.1, 8.8.8.8 etc.

EDIT: Please follow these instructions:

Execute sudo rm /etc/resolv.conf

Execute sudo touch /etc/resolv.conf

Edit the file with sudo nano /etc/resolv.conf

Add this line to the file: nameserver 1.1.1.1

Press ctrl + s to save and ctrl + x to exit

Restart the service:

sudo systemctl restart systemd-resolved.service

Then try to access the internet again. If it still doesn't work, reboot the system and try again. That should solve your problem.

Answer 2

This is what helped in my case:

Ubuntu is now using systemd-resolve, which is controlled by resolvectl.

I found that no nameservers were configured:

$ resolvectl dns
Global:
Link 2 (enp1s0):
Link 3 (wlp2s0):

So I added one:

$ resolvectl dns wlp2s0 8.8.8.8 8.8.4.4 1.1.1.1

and now DNS lookup works!

$ nslookup example.com
Server:     127.0.0.53
Address:    127.0.0.53#53

Non-authoritative answer:
Name:   example.com
Address: 93.184.215.14
Name:   example.com
Address: 2606:2800:21f:cb07:6820:80da:af6b:8b2c

Answer 3

Firstly, I have to give a shout out to @chili555 for spending literally hours last night helping me troubleshoot.

After many hours of troubleshooting, the simplest answer was the solution. Something must have gone wrong during installation, because after a reinstall from the same usb flash drive, my computer is on the network and accessing the internet.

I still don't know the true cause, but my server is up and running.

Thanks @chili555!

Answer 4

Adding to the discussion here, I had a similar issue with my Xubutu 22.10 + gnome today.

In the past, recreating resolv.conf had helped me for a similar issue, but today it did not.

Ultimately I realised that I had a VPN client (windscribe) installed that I had switched off recently. As soon as I used the .Deb file to uninstall the package, my internet came back.

I'm leaving this resolution here for others who might have a similar issue.