今天，在我运行sudo apt-get update命令后，我得到了一个NO_PUBKEY错误。我试图解决方案，从这里，这里和这里（创建文件伎俩）。尽管如此，它们都没有工作，我仍然收到以下错误：
W: GPG error: http://archive.canonical.com precise Release: The following signatures were invalid: 630239CC130E1A7FD81A27B140976EAF437D05B5
W: The repository 'http://archive.canonical.com precise Release' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
所以，特别是我在打字时得到的
sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com --recv-keys 630239CC130E1A7FD81A27B140976EAF437D05B5
是
Executing: /tmp/apt-key-gpghome.FQVhh2ndBW/gpg.1.sh --keyserver hkp://keyserver.ubuntu.com --recv-keys 630239CC130E1A7FD81A27B140976EAF437D05B5
gpg: key 40976EAF437D05B5: "Ubuntu …