树莓派安装mono

http://www.mono-project.com/download/

sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF

出现错误
Executing: /tmp/apt-key-gpghome.ZqIcif1Acm/gpg.1.sh --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EFgpg: failed to start the dirmngr '/usr/bin/dirmngr': No such file or directorygpg: connecting dirmngr at '/tmp/apt-key-gpghome.ZqIcif1Acm/S.dirmngr' failed: No such file or directorygpg: keyserver receive failed: No dirmngr

根据关键信息 gpg: keyserver receive failed: No dirmngr
$ sudo apt-cache search -n dirmngr
得到
dirmngr - GNU privacy guard - network certificate management service
安装软件
$ sudo apt-get install dirmngr

出现错误

pi@raspberrypi:~/workdir $ sudo apt-get install vsftpd Reading package lists... Done Building dependency tree Reading state information... Done The following extra packages will be installed: dialog ssl-cert Suggested packages: openssl-blacklist The following NEW packages will be installed: dialog ssl-cert vsftpd 0 upgraded, 3 newly installed, 0 to remove and 0 not upgraded. Need to get 139 kB/393 kB of archives. After this operation, 1,106 kB of additional disk space will be used. Do you want to continue? [Y/n] y Err http://mirrordirector.raspbian.org/raspbian/ jessie/main vsftpd armhf 3.0.2-17 404 Not Found [IP: 5.153.225.207 80] E: Failed to fetch http://mirrordirector.raspbian.org/raspbian/pool/main/v/vsftpd/vsftpd_3.0.2-17_armhf.d eb 404 Not Found [IP: 5.153.225.207 80] E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

root@raspberrypi:/home/pi/workdir# apt-get update

再次安装软件
$ sudo apt-get install dirmngr

再次
$ sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF

echo "deb http://download.mono-project.com/repo/debian raspbianstretch main" | sudo tee /etc/apt/sources.list.d/mono-official.list

sudo apt-get update

安装 mono develop

https://www.maketecheasier.com/write-c-sharp-programs-raspberry-pi/