Software Update: This requires installing packages from unauthenticated sources

When trying to install packages through the software updater on Ubuntu 14.04.1 LTS I get following error:

Software Updater error

It's about these packages: Software Updates packages

I have selected following settings from where to install updates from: Software & Updates settings

I have run following commands:

sudo apt-get clean
sudo apt-get update
sudo apt-get upgrade

sudo apt-get update gives following output:

Reading package lists... Done
W: GPG error: https://download.01.org trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A902DDA375E52366
W: Duplicate sources.list entry http://dl.google.com/linux/chrome/deb/ stable/main i386 Packages (/var/lib/apt/lists/dl.google.com_linux_chrome_deb_dists_stable_main_binary-i386_Packages)

sudo apt-get upgrade gives following output:

The following packages have been kept back:
  libegl1-mesa libegl1-mesa-drivers libgbm1 libgl1-mesa-dri libgl1-mesa-glx
  libglapi-mesa libgles1-mesa libgles2-mesa libosmesa6 liboxideqt-qmlplugin
  liboxideqtcore0 libwayland-egl1-mesa libxatracker2 linux-generic
  linux-generic-pae linux-headers-generic linux-headers-generic-pae
  linux-image-generic linux-image-generic-pae oxideqt-codecs
  python-cupshelpers system-config-printer-gnome
0 upgraded, 0 newly installed, 0 to remove and 22 not upgraded.

UPDATE

With question How do I deal with "unauthenticated sources" errors in the Software Center?

issueing following commands:

sudo apt-get clean
cd /var/lib/apt
sudo mv lists lists.old
sudo mkdir -p lists/partial
sudo apt-get clean
sudo apt-get update

still gives following output:

Reading package lists... Done
W: GPG error: https://download.01.org trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A902DDA375E52366
W: Duplicate sources.list entry http://dl.google.com/linux/chrome/deb/ stable/main i386 Packages (/var/lib/apt/lists/dl.google.com_linux_chrome_deb_dists_stable_main_binary-i386_Packages)

Followed the second answer:

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys A902DDA375E52366
sudo apt-get update

but receive following error:

W: Duplicate sources.list entry http://dl.google.com/linux/chrome/deb/ stable/main i386 Packages (/var/lib/apt/lists/dl.google.com_linux_chrome_deb_dists_stable_main_binary-i386_Packages)
W: You may want to run apt-get update to correct these problems

and apt-get update doesn't correct the problem


You could run:

sudo apt-get update && sudo apt-get dist-upgrade

To fix the duplicate entry in your sources.list file:

Open it in an editor with root/sudo rights e.g:

sudo nano /etc/apt/sources.list

and remove the duplicate line (does not matter which):

http://dl.google.com/linux/chrome/deb/

Then use ctrl-x to exit (y to save). Do an apt-get update and upgrade as you normally would.