Oracle Repository GPG/PGP Key
If you’re using the Oracle apt repository (deb http://oss.oracle.com/debian/ unstable main non-free) with Ubuntu or a recent version of Debian and don’t have their GPG key, you’ll get the following error when running apt-get update:
W: GPG error: http://oss.oracle.com unstable Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 2E2BCDBCB38A8516
W: You may want to run apt-get update to correct these problems
To fix this, you need to add Oracle’s key to apt, which is straightforward, if you can find the key. After some searching, I found it at http://oss.oracle.com/el4/RPM-GPG-KEY-oracle; to import this, run the following:
sudo wget http://oss.oracle.com/el4/RPM-GPG-KEY-oracle -O- | sudo apt-key add -