gpg: la recepción del servidor de claves ha fallado: no hay dirmngr

Al intentar recibir claves en mi servidor Debian Stretch, aparece este error:

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

Instalar el paquete dirmngrsolucionó el error.

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

Reintentando:

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

No pude hacer que dirmngr funcionara, pero también puedes importar la clave directamente usando apt-key add. La clave pública GPG a menudo aparece en la raíz del repositorio como http://origin-download.mono-project.com/repo/

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