gnupg, gnupg2 and gnupg1 do not seem to be installed, but one of them is required for this operation

apt-key adv --keyserver pgp.mit.edu --recv-keys ED444FF07D8D0BF6
给服务器添加公钥时报错如下：
gnupg, gnupg2 and gnupg1 do not seem to be installed, but one of them is required for this operation
uploading-image-303658.png

解决方法
在添加密钥之前执行
apt-get update && apt-get install -y gnupg2