I came across this error while doing sudo apt-get update
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 5A9BF3BB4E5E19B8
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 9ABD05E22847688C
This made me do some hunting on the web. I tried quite a few solutions out of which the following worked.
Run the following command in terminal:
gpg --keyserver subkeys.pgp.net --recv 5A9BF3BB4E5E19B8
gpg --export --armor 5A9BF3BB4E5E19B8 | sudo apt-key add –
Replace 5A9BF3BB4E5E19B8 with your own key. This solved the error. I repeated the procedure for second key and I stopped getting error messages.
On the first command, sometimes the server maybe down. In that case you can try the following servers.
hkp://subkeys.pgp.net
hkp://pgp.mit.edu
hkp://pool.sks-keyservers.net
hkp://keys.nayr.net
http://keys.gnupg.net
To use these servers just replace subkeys.pgp.net with any of the server above. For eg;
gpg --keyserver http://keys.gnupg.net --recv 5A9BF3BB4E5E19B8
Source:
http://gentoo-blog.de/ubuntu/ubuntu-gpg-error-httpppalaunchpadnet-intrepid-release/
Cheers!