root@izul-webserver:~# wget http://www.webmin.com/jcameron-key.asc -O - | apt-key add -
--2015-01-31 14:30:46--  http://www.webmin.com/jcameron-key.asc
Resolving www.webmin.com (www.webmin.com)... failed: Name or service not known.
wget: unable to resolve host address ‘www.webmin.com’
gpg: no valid OpenPGP data found.
root@izul-webserver:~# apt-get update
Err http://security.ubuntu.com saucy-security InRelease

Err http://id.archive.ubuntu.com saucy InRelease

Err http://id.archive.ubuntu.com saucy-updates InRelease

Err http://id.archive.ubuntu.com saucy-backports InRelease

Err http://security.ubuntu.com saucy-security Release.gpg
  Could not resolve 'security.ubuntu.com'
Err http://id.archive.ubuntu.com saucy Release.gpg
  Could not resolve 'id.archive.ubuntu.com'
Err http://id.archive.ubuntu.com saucy-updates Release.gpg
  Could not resolve 'id.archive.ubuntu.com'
Err http://id.archive.ubuntu.com saucy-backports Release.gpg
  Could not resolve 'id.archive.ubuntu.com'
Err http://download.webmin.com sarge InRelease

Err http://download.webmin.com sarge Release.gpg
  Could not resolve 'download.webmin.com'
Reading package lists... Done
W: Failed to fetch http://id.archive.ubuntu.com/ubuntu/dists/saucy/InRelease

W: Failed to fetch http://id.archive.ubuntu.com/ubuntu/dists/saucy-updates/InRelease

W: Failed to fetch http://id.archive.ubuntu.com/ubuntu/dists/saucy-backports/InRelease

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/saucy-security/InRelease

W: Failed to fetch http://download.webmin.com/download/repository/dists/sarge/InRelease

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/saucy-security/Release.gpg  Could not resolve 'security.ubuntu.com'

W: Failed to fetch http://id.archive.ubuntu.com/ubuntu/dists/saucy/Release.gpg  Could not resolve 'id.archive.ubuntu.com'

W: Failed to fetch http://id.archive.ubuntu.com/ubuntu/dists/saucy-updates/Release.gpg  Could not resolve 'id.archive.ubuntu.com'

W: Failed to fetch http://id.archive.ubuntu.com/ubuntu/dists/saucy-backports/Release.gpg  Could not resolve 'id.archive.ubuntu.com'

W: Failed to fetch http://download.webmin.com/download/repository/dists/sarge/Release.gpg  Could not resolve 'download.webmin.com'

W: Some index files failed to download. They have been ignored, or old ones used instead.

this mean, your problem on your DNS, chang it to google DNS 8.8.8.8

vim /etc/resolvconf/resolv.conf.d/head

put your nameserver list in

nameserver 8.8.8.8
nameserver 8.8.4.4

then run

resolvconf -u

 references:
http://ubuntuforums.org/showthread.php?t=2078398
https://www.netroby.com/view.php?id=3630#.U2mTfHVdUc0

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