I tried updating ubuntu mate 16.04 using software updater and it shows me the apps that going to be updated but everytime I click “Install Now” a pop-up message
"Requires installation of untrusted packages (This requires installing packages from unauthenticated sources)".
Every time I click the button “OK” the message disappears and nothing happens no updating. I always had no problem updating and this is the first time I encountered this message. Kindly help me guys…
Can you please show the content of /etc/apt/sources.list?
Hello! Here is the contents of /etc/apt/ source.list:
# deb cdrom:[Ubuntu-MATE 16.04.2 LTS _Xenial Xerus_ - Release i386 (20170215)]/ xenial main multiverse restricted universe
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://archive.ubuntu.com/ubuntu xenial main restricted
deb-src http://archive.ubuntu.com/ubuntu xenial universe restricted main multiverse #Added by software-properties
# deb-src http://ph.archive.ubuntu.com/ubuntu/ xenial main restricted
## Major bug fix updates produced after the final release of the
## distribution.
deb http://archive.ubuntu.com/ubuntu xenial-updates main restricted
deb-src http://archive.ubuntu.com/ubuntu xenial-updates universe restricted main multiverse #Added by software-properties
# deb-src http://ph.archive.ubuntu.com/ubuntu/ xenial-updates main restricted
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://archive.ubuntu.com/ubuntu xenial universe
# deb-src http://ph.archive.ubuntu.com/ubuntu/ xenial universe
deb http://archive.ubuntu.com/ubuntu xenial-updates universe
# deb-src http://ph.archive.ubuntu.com/ubuntu/ xenial-updates universe
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://archive.ubuntu.com/ubuntu xenial multiverse
# deb-src http://ph.archive.ubuntu.com/ubuntu/ xenial multiverse
deb http://archive.ubuntu.com/ubuntu xenial-updates multiverse
# deb-src http://ph.archive.ubuntu.com/ubuntu/ xenial-updates multiverse
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://archive.ubuntu.com/ubuntu xenial-backports main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu xenial-backports main restricted universe multiverse #Added by software-properties
# deb-src http://ph.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse
## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
deb http://archive.canonical.com/ubuntu xenial partner
deb-src http://archive.canonical.com/ubuntu xenial partner
deb http://archive.ubuntu.com/ubuntu xenial-security main restricted
deb-src http://archive.ubuntu.com/ubuntu xenial-security universe restricted main multiverse #Added by software-properties
# deb-src http://security.ubuntu.com/ubuntu xenial-security main restricted
deb http://archive.ubuntu.com/ubuntu xenial-security universe
# deb-src http://security.ubuntu.com/ubuntu xenial-security universe
deb http://archive.ubuntu.com/ubuntu xenial-security multiverse
# deb-src http://security.ubuntu.com/ubuntu xenial-security multiverse
And every time I use sudo apt-get update command in terminal it has this error:
Ign:13 https://download.01.org/gfx/ubuntu/16.04/main xenial InRelease
Fetched 334 kB in 7s (41.8 kB/s)
Reading package lists... Done
W: GPG error: https://download.01.org/gfx/ubuntu/16.04/main xenial InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 56A3DEF863961D39
W: The repository 'https://download.01.org/gfx/ubuntu/16.04/main xenial InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
Hope this helps. Thank you in advance 
I think that you installed the Intel Graphics Drivers repository rex_everett_Tibus.
https://01.org/linuxgraphics/downloads/intel-graphics-update-tool-linux-os-v2.0.2
To make Ubuntu trust future updates from the Intel repository, you have to run the command below in terminal (Ctrl+Alt+T) to setup the key:
wget --no-check-certificate https://download.01.org/gfx/RPM-GPG-KEY-ilg-4 -O - | sudo apt-key add -
Failure to do that results in stuff like your error message above.
you're a genius brother! thank you it worked.
Glad to hear that. Onward and upward as one of my friends would say.