How to resolve domain name resolution issues in Ubuntu?

If Ubuntu is unable to resolve domain names, it may be due to the following reasons: 1. Incorrect DNS settings: Ensure that your Ubuntu system is configured with the correct DNS server. You can check the DNS server settings in the `/etc/resolv.conf` file and make sure they are correct. 2. DNS server malfunction: If the DNS server is down, it may cause Ubuntu to be unable to resolve domain names. You can try using another reliable DNS server. 3. Network connection issues: Check if your network connection is functioning properly. Ensure that your Ubuntu system can access the Internet normally and that no firewall or proxy settings are blocking DNS resolution. 4. Incorrect hosts file configuration: Check the `/etc/hosts` file to ensure there are no errors in the domain name resolution settings. This file can manually configure domain name resolution, and any misconfigurations may lead to resolution failures. 5. DNS cache issues: Try clearing the DNS cache on your Ubuntu system. You can use the following command to clear the DNS cache:

  sudo systemctl restart systemd-resolved.service

If the above methods fail to solve the problem, further investigation into network settings or contacting your internet service provider may be necessary to resolve the issue.