Debian 密鑰環錯誤：“未安裝密鑰環”

我有一個 Debian Squeeze EC2 AMI。在使用它啟動實例並嘗試使用 apt-get 安裝軟體包時，我收到錯誤消息，指出沒有安裝密鑰環。這是 apt-get update 的錯誤：

root@ip:~# apt-get update
Get:1 http://ftp.us.debian.org squeeze Release.gpg [1672 B]
Ign http://ftp.us.debian.org/debian/ squeeze/contrib Translation-en
Ign http://ftp.us.debian.org/debian/ squeeze/main Translation-en
Ign http://ftp.us.debian.org/debian/ squeeze/non-free Translation-en
Get:2 http://security.debian.org squeeze/updates Release.gpg [836 B]          
Ign http://security.debian.org/ squeeze/updates/contrib Translation-en                                  
Ign http://security.debian.org/ squeeze/updates/main Translation-en           
Hit http://ftp.us.debian.org squeeze Release                                  
Ign http://ftp.us.debian.org squeeze Release                                                         
Ign http://security.debian.org/ squeeze/updates/non-free Translation-en                              
Ign http://ftp.us.debian.org squeeze/main Sources/DiffIndex                                         
Get:3 http://security.debian.org squeeze/updates Release [86.9 kB]                                  
Ign http://security.debian.org squeeze/updates Release                         
Ign http://ftp.us.debian.org squeeze/contrib Sources/DiffIndex          
Ign http://ftp.us.debian.org squeeze/non-free Sources/DiffIndex
Ign http://ftp.us.debian.org squeeze/main amd64 Packages/DiffIndex
Ign http://ftp.us.debian.org squeeze/contrib amd64 Packages/DiffIndex
Ign http://ftp.us.debian.org squeeze/non-free amd64 Packages/DiffIndex
Ign http://security.debian.org squeeze/updates/main Sources/DiffIndex
Hit http://ftp.us.debian.org squeeze/main Sources                    
Hit http://ftp.us.debian.org squeeze/contrib Sources
Hit http://ftp.us.debian.org squeeze/non-free Sources
Hit http://ftp.us.debian.org squeeze/main amd64 Packages             
Hit http://ftp.us.debian.org squeeze/contrib amd64 Packages          
Ign http://security.debian.org squeeze/updates/contrib Sources/DiffIndex
Ign http://security.debian.org squeeze/updates/non-free Sources/DiffIndex
Ign http://security.debian.org squeeze/updates/main amd64 Packages/DiffIndex
Ign http://security.debian.org squeeze/updates/contrib amd64 Packages/DiffIndex
Ign http://security.debian.org squeeze/updates/non-free amd64 Packages/DiffIndex
Hit http://ftp.us.debian.org squeeze/non-free amd64 Packages         
Get:4 http://backports.debian.org squeeze-backports Release.gpg [836 B]
Ign http://backports.debian.org/debian-backports/ squeeze-backports/main Translation-en
Hit http://security.debian.org squeeze/updates/main Sources
Hit http://security.debian.org squeeze/updates/contrib Sources
Hit http://security.debian.org squeeze/updates/non-free Sources
Hit http://security.debian.org squeeze/updates/main amd64 Packages
Hit http://security.debian.org squeeze/updates/contrib amd64 Packages
Hit http://security.debian.org squeeze/updates/non-free amd64 Packages
Get:5 http://backports.debian.org squeeze-backports Release [77.6 kB]
Ign http://backports.debian.org squeeze-backports Release
Hit http://backports.debian.org squeeze-backports/main amd64 Packages/DiffIndex
Hit http://backports.debian.org squeeze-backports/main amd64 Packages
Fetched 3346 B in 0s (5298 B/s)
Reading package lists... Done
W: GPG error: http://ftp.us.debian.org squeeze Release: No keyring installed in /etc/apt/trusted.gpg.d/.
W: GPG error: http://security.debian.org squeeze/updates Release: No keyring installed in /etc/apt/trusted.gpg.d/.
W: GPG error: http://backports.debian.org squeeze-backports Release: No keyring installed in /etc/apt/trusted.gpg.d/.

Google搜尋並沒有真正幫助我解決這個問題。我嘗試安裝軟體包“debian-keyring”和“debian-archive-keyring”，但錯誤並沒有消失。我想避免安裝不受信任的軟體包。任何幫助表示讚賞！為什麼會發生此錯誤，我在哪裡可以了解更多資訊？

最後用以下方法解決了這個問題：

wget --no-check-certificate https://ftp-master.debian.org/keys/archive-key-6.0.asc
&& apt-key add archive-key-6.0.asc
apt-get update
apt-get install --reinstall debian-keyring debian-archive-keyring
apt-get update

引用自：https://serverfault.com/questions/446202