Ubuntu安装Jenkins是报错：The following signatures couldn't be verified because the public key is not available: NO_PUBKEY XXXXXXXXXXX

　　我使用Ubuntu16.04安装Jenkins时，按照官网的要求，步骤如下（https://pkg.jenkins.io/debian-stable/）：　　

    # 添加Key
    sudo wget -q -O - https://pkg.jenkins.io/debian-stable/jenkins.io.key | sudo apt-key add -
　　 # 添加包源,可以打开/etc/apt/sources.list，添加一行：deb https://pkg.jenkins.io/debian-stable binary/
　　 # sudo vim /etc/apt/sources.list
　　 # 或者使用下面的命令追加到包源文件
　　 sudo sh -c 'echo deb http://pkg.jenkins.io/debian-stable binary/ > /etc/apt/sources.list.d/jenkins.list'
　　 # 更新包源
　　 sudo apt-get update
　　 # 安装jenkins
　　 sudo apt-get install jenkins

　　但是在执行更新包源时，报错了：The following signatures couldn't be verified because the public key is not available: NO_PUBKEY FCEF32E745F2C3D5

　　 Reading package lists... Done
　　 W: GPG error: https://pkg.jenkins.io/debian-stable binary/ Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY FCEF32E745F2C3D5
　　 W: The repository 'http://pkg.jenkins.io/debian-stable binary/ 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.

　　这个是说由于没有公钥，无法验证下列签名，解决办法是添加上面的公钥，比如上面的信息说我的公钥是：FCEF32E745F2C3D5

　　于是我就执行下面的命令：　　

    # 最后的参数就是公钥
　　 sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys FCEF32E745F2C3D5

　　执行完之后，再执行 sudo apt-get update 就不会报错了，但是可能有其它的错，比如连接失败等等，多试几次就好了。

　　不过最后的install十次有9次会失败，看人品了。