apt-get update 할때
W: GPG error: http://ppa.launchpad.net precise Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY EAA903E3A2F4C055
위와 같이 에러가 뜬다면
# apt-key adv --keyserver keyserver.ubuntu.com --recv-keys EAA903E3A2F4C055
Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --secret-keyring /tmp/tmp.iQj4LjUa8u --trustdb-name /etc/apt/trustdb.gpg --keyring /etc/apt/trusted.gpg --primary-keyring /etc/apt/trusted.gpg --keyserver keyserver.ubuntu.com --recv-keys EAA903E3A2F4C039
gpg: requesting key A2F4C039 from hkp server keyserver.ubuntu.com
gpg: key A2F4C039: public key "Launchpad Subversion" imported
gpg: Total number processed: 1
gpg: imported: 1 (RSA: 1)
#
해주면 에러없이 정상적으로 updage 할수 있다.