All was working perfectly until the update. Today I thought that some security updates of packages will be better for our server security. So, I have updated only security updates using Webmin(webmin.com) after all updates completed without any errors and automatically rebooted our server.
after that when I tried to run
sudo command(was 'sudo cp') but it was showing error like cannot find ip-172-1-1-1(IP of ec2) host then i solved that by adding a line:
then when tried to run
sudo certbot --apache then it was showing error: command not found! (I was shocked because previously it was installed and working perfectly without any error). and then i have noticed that my login welcome of Ubuntu has changed previously there were an update notice for Ubuntu 18 and now there is showing an error:
Failed to connect to https://changelogs.ubuntu.com/meta-release-lts. Check your Internet connection or proxy settings and then i tried ping google.com and it is saying now:
ping: unknown host google.com
*** Please help me, I'm not very familiar with Networking and System Administration, I just learned to do necessary things in order to deploy my client Applications(Laravel, Slim, PHP etc) such as: apache2, certbot(LetsEncrypt), php config, webmin, roundcube, service: start, restart, reload etc commands.