root@ubuntu:/# apt update
Err:1 http://in.archive.ubuntu.com/ubuntu bionic InRelease
  Temporary failure resolving 'in.archive.ubuntu.com'
Err:2 http://in.archive.ubuntu.com/ubuntu bionic-updates InRelease
  Temporary failure resolving 'in.archive.ubuntu.com'
Err:3 http://archive.canonical.com/ubuntu bionic InRelease
  Temporary failure resolving 'archive.canonical.com'
Err:4 http://security.ubuntu.com/ubuntu bionic-security InRelease
  Temporary failure resolving 'security.ubuntu.com'
Err:5 http://dl.google.com/linux/chrome/deb stable InRelease
  Temporary failure resolving 'dl.google.com'
Err:6 http://packages.ros.org/ros/ubuntu bionic InRelease
  Temporary failure resolving 'packages.ros.org'
Err:7 http://ppa.launchpad.net/tsbarnes/indicator-keylock/ubuntu bionic InRelease
  Temporary failure resolving 'ppa.launchpad.net'
Err:8 http://repository.spotify.com stable InRelease
  Temporary failure resolving 'repository.spotify.com'
Err:9 https://download.sublimetext.com apt/stable/ InRelease
  Temporary failure resolving 'download.sublimetext.com'
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.
W: Failed to fetch http://in.archive.ubuntu.com/ubuntu/dists/bionic/InRelease  Temporary failure resolving 'in.archive.ubuntu.com'
W: Failed to fetch http://in.archive.ubuntu.com/ubuntu/dists/bionic-updates/InRelease  Temporary failure resolving 'in.archive.ubuntu.com'
W: Failed to fetch http://archive.canonical.com/ubuntu/dists/bionic/InRelease  Temporary failure resolving 'archive.canonical.com'
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/bionic-security/InRelease  Temporary failure resolving 'security.ubuntu.com'
W: Failed to fetch http://dl.google.com/linux/chrome/deb/dists/stable/InRelease  Temporary failure resolving 'dl.google.com'
W: Failed to fetch http://packages.ros.org/ros/ubuntu/dists/bionic/InRelease  Temporary failure resolving 'packages.ros.org'
W: Failed to fetch http://repository.spotify.com/dists/stable/InRelease  Temporary failure resolving 'repository.spotify.com'
W: Failed to fetch https://download.sublimetext.com/apt/stable/InRelease  Temporary failure resolving 'download.sublimetext.com'
W: Failed to fetch http://ppa.launchpad.net/tsbarnes/indicator-keylock/ubuntu/dists/bionic/InRelease  Temporary failure resolving 'ppa.launchpad.net'
W: Some index files failed to download. They have been ignored, or old ones used instead.
root@ubuntu:/#