Err:1 http://security.ubuntu.com/ubuntu xenial-security InRelease Temporary failure resolving ‘security.ubuntu.com’ Err:2 http://archive.ubuntu.com/ubuntu xenial InRelease Temporary failure resolving ‘archive.ubuntu.com’ Err:3 http://archive.ubuntu.com/ubuntu xenial-updates InRelease Temporary failure resolving ‘archive.ubuntu.com’Reading package lists… DoneW: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial/InRelease Temporary failure resolving ‘archive.ubuntu.com'W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-updates/InRelease Temporary failure resolving ‘archive.ubuntu.com'W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/xenial-security/InRelease Temporary failure resolving ‘security.ubuntu.com'W: Some index files failed to download. They have been ignored, or old ones used instead ...