Installing software packages can be achieved in many ways. You can use a Gui (Graphical user interface) or using the good old command line. For those of you who want to keep it neat and discreet by using a gui, you can download a package installation manager (PPA-manager) from lets say the webupd8team repository, by simply typing the simple command:
sudo add-apt-repository ppa:webupd8team/y-ppa-manager
sudo apt-get update
sudo apt-get install y-ppa-manager
For those interested in doing it the old fashioned way using command line, there are several methods of ensuring that PPA keys can be installed and validity verified. There are two most common methods one can use.
First , grab a copy of the key number. In case, the key number is 68A3CE6B38BD81CA for instance. Change the key according to the number if you get such an error.
W: GPG error: http://ppa.launchpad.net karmic Release: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY 68A3CE6B38BD81CA
Launch a terminal window (Applications > Accessories >Terminal) and execute the following commands and then Press ENTER after typing in each command.
gpg –keyserver subkeys.pgp.net –recv 68A3CE6B38BD81CA
gpg –export –armor 68A3CE6B38BD81CA | sudo apt-key add –
If everything was successful, you should not get a GPG error the next time you perform an update.
NB. If you want to manually verify the keys from the PPA repos you can use the command below to list installed repository and newly added keys.
sudo apt-key list
The output will be simmilar to :
pub 1024D/437D05B5 2004-09-12
uid Ubuntu Archive Automatic Signing Key <firstname.lastname@example.org>
sub 2048g/79164387 2004-09-12
pub 1024D/FBB75451 2004-12-30
uid Ubuntu CD Image Automatic Signing Key <email@example.com>
pub 1024D/3E5C1192 2010-09-20
uid Ubuntu Extras Archive Automatic Signing Key <firstname.lastname@example.org>
pub 2048R/5044912E 2010-02-11
uid Dropbox Automatic Signing Key <email@example.com>
pub 1024R/5879C434 2011-09-21
uid Launchpad PPA for Claudio Novais
pub 1024D/7FAC5991 2007-03-08
uid Google, Inc. Linux Package Signing Key <firstname.lastname@example.org>
sub 2048g/C07CB649 2007-03-08
pub 1024R/4E5E17B5 2009-02-25
uid Launchpad PPA for chromium-daily
pub 1024R/4631BBEA 2010-06-04
uid Launchpad equinoxart
pub 1024R/8844C542 2009-01-20
uid Launchpad PPA for xorg crack pushers
pub 1024R/854C4636 2009-04-01
uid Launchpad PPA for Robert Hooker
Enter this final command in a terminal to test if key installation was successful.
sudo apt-key adv –keyserver keyserver.ubuntu.com –recv-keys 68A3CE6B38B
sudo apt-get update
sudo apt-get upgrade
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