/etc/resolv.conf？
Err:4 http://np.archive.ubuntu.com/ubuntu xenial Release
403 Forbidden
Err:5 http://np.archive.ubuntu.com/ubuntu xenial-updates Release
403 Forbidden
Err:6 http://np.archive.ubuntu.com/ubuntu xenial-backports Release
403 Forbidden
Get:7 http://security.ubuntu.com/ubuntu xenial-security InRelease [102 kB]
Hit:8 http://ppa.launchpad.net/webupd8team/sublime-text-3/ubuntu xenial InRelease
Reading package lists... Done
E: The repository 'http://np.archive.ubuntu.com/ubuntu xenial Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://np.archive.ubuntu.com/ubuntu xenial-updates Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://np.archive.ubuntu.com/ubuntu xenial-backports Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.