gpg：密钥服务器接收失败：没有dirmngr

尝试在Debian Stretch服务器中接收密钥时，出现以下错误：

sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
Executing: /tmp/apt-key-gpghome.4B7hWtn7Rm/gpg.1.sh --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
gpg: failed to start the dirmngr '/usr/bin/dirmngr': No such file or directory
gpg: connecting dirmngr at '/tmp/apt-key-gpghome.4B7hWtn7Rm/S.dirmngr' failed: No such file or directory
gpg: keyserver receive failed: No dirmngr

安装软件包dirmngr可修复该错误。

user@debian-server:~$ sudo apt-get install dirmngr

重试：

user@debian-server:~$ sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
Executing: /tmp/apt-key-gpghome.haKuPppywi/gpg.1.sh --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
gpg: key A6A19B38D3D831EF: public key "Xamarin Public Jenkins (auto-signing) <releng@xamarin.com>" imported
gpg: Total number processed: 1
gpg:               imported: 1

我无法使dirmngr正常工作，但是您也可以直接使用apt-key add导入密钥。GPG公钥通常在回购协议的根目录中列出，例如http://origin-download.mono-project.com/repo/

curl https://origin-download.mono-project.com/repo/xamarin.gpg | sudo apt-key add -