為什麼無法獲得 R 反向移植的 CRAN 密鑰？

我做得到

# http://stackoverflow.com/a/10260634/54964
root@masi:/home/masi/Documents# gpg --keyserver subkeys.pgp.net --recv-key  06F90DE5381BA480
gpg: directory `/root/.gnupg' created
gpg: new configuration file `/root/.gnupg/gpg.conf' created
gpg: WARNING: options in `/root/.gnupg/gpg.conf' are not yet active during this run
gpg: keyring `/root/.gnupg/secring.gpg' created
gpg: keyring `/root/.gnupg/pubring.gpg' created
gpg: requesting key 381BA480 from hkp server subkeys.pgp.net
?: subkeys.pgp.net: Network is unreachable
gpgkeys: HTTP fetch error 7: couldn't connect: Network is unreachable
gpg: no valid OpenPGP data found.
gpg: Total number processed: 0

我正在嘗試更改為 R 反向移植，因為我需要 R 3.3.2，所以我已經添加了以下行/etc/apt/sources.list

deb http://cran.wu.ac.at/bin/linux/debian jessie-cran3/

迭代 rcs 的提議

root@masi:/home/masi/Documents# gpg --keyserver keys.gnupg.net --recv-key 06F90DE5381BA480
gpg: requesting key 381BA480 from hkp server keys.gnupg.net
gpg: /root/.gnupg/trustdb.gpg: trustdb created
gpg: key 381BA480: public key "Johannes Ranke (CRAN Debian archive) <jranke@uni-bremen.de>" imported
gpg: no ultimately trusted keys found
gpg: Total number processed: 1
gpg:               imported: 1

root@masi:/home/masi/Documents# apt-get update
...
Fetched 116 kB in 3s (32.1 kB/s)         
Reading package lists... Done
W: GPG error: http://cran.wu.ac.at jessie-cran3/ Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 06F90DE5381BA480

作業系統：Debian 8.5

請參閱CRAN 上 Debian 軟體包的安裝說明， Secure apt部分：

CRAN 上的 Debian 反向移植檔案使用 Johannes Ranke（CRAN Debian 檔案）的密鑰簽名，密鑰指紋為 6212 B7B7 931C 4BB1 6280 BA13 06F9 0DE5 381B A480。您可以使用

apt-key adv --keyserver keys.gnupg.net --recv-key 6212B7B7931C4BB16280BA1306F90DE5381BA480

引用自：https://unix.stackexchange.com/questions/324543