How to fix GPG errors in Ubuntu

Problem: When running sudo apt-get update, you get a bunch of errors such as

W: GPG error: http://ppa.launchpad.net oneiric Release: The following signatures
couldn't be verified because the public key is not available: NO_PUBKEY 6E871C4A881574DE

And because of this, you can’t run the update. There are a couple of fixes for this.

First, there’s the standard suite of commands:

sudo apt-get clean

sudo rm -r /var/lib/apt/lists/*

sudo touch /var/lib/apt/lists/lock

sudo mkdir /var/lib/apt/lists/partial

sudo apt-get clean

sudo apt-get update

If these don’t work you may need to manually re-download the keys.

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys hex_key_here

Substituting the actually key for hex_key_here. The key is the long hexadecimal number at the end of the ap-get update error. Using the example I gave above, I would type into my terminal

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 6E871C4A881574DE

AND do yourself a favor and copy/paste the keys and/or the commands rather than manually typing them. One error is all it takes to make a lot of frustration.

If this stuff doesn’t work, there may be more info here: http://ubuntuforums.org/showthread.php?t=1221323

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