If you get an error like the following from apt:
W: GPG error: http://ppa.launchpad.net lucid Release: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY A6DCF7707EBC211F
Take the last 8 characters of the string in the error message and use it in the following two commands:
gpg --keyserver keyserver --recv 7EBC211F
The keyserver in the above commands may be a server like
keyserver.ubuntu.com or pgp.mit.edu.
The above command will generate an output similar to the following:
gpg: requesting key 7EBC211F from hkp server keyserver.ubuntu.com gpg: key 7EBC211F: public key “Launchpad PPA for Ubuntu Mozilla Security Team” imported gpg: no ultimately trusted keys found gpg: Total number processed: 1 gpg: imported: 1 (RSA: 1)
Next, run the following command:
gpg --export --armor 7EBC211F | sudo apt-key add -
The above command should generate the following output:
OK
Note the post at http://askubuntu.com/a/127187 suggest that the above two steps can be performed in a single steps. I need to try out this command.
sudo apt-key adv --keyserver keyserver --recv-keys 7EBC211F
References