APT GPG Key 錯誤

使用 apt-get update 發生的錯誤：

W: GPG error: http://security.debian.org lenny/updates Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 9AA38DCD55BE302B
W: There is no public key available for the following key IDs:
9AA38DCD55BE302B
W: You may want to run apt-get update to correct these problems

修正方法：
# gpg --keyserver wwwkeys.eu.pgp.net --recv-keys 9AA38DCD55BE302B
# apt-key add /root/.gnupg/pubring.gpg
# apt-get update