apt-get update在 ubuntu 10.04 伺服器上運行（輸出如下）後，我發現了這個問題。在此之前我已經刪除了apt-key.我在哪裡可以得到這個apt-key來再次添加它？
Get:1 http://security.ubuntu.com lucid-security Release.gpg [198B]
Ign http://security.ubuntu.com/ubuntu/ lucid-security/main Translation-en_IN
Ign http://security.ubuntu.com/ubuntu/ lucid-security/restricted Translation-en_IN
Get:2 http://in.archive.ubuntu.com lucid Release.gpg [189B]
Ign http://in.archive.ubuntu.com/ubuntu/ lucid/main Translation-en_IN
Ign http://in.archive.ubuntu.com/ubuntu/ lucid/restricted Translation-en_IN
Ign http://security.ubuntu.com/ubuntu/ lucid-security/universe Translation-en_IN
Ign http://security.ubuntu.com/ubuntu/ lucid-security/multiverse Translation-en_IN
Get:3 http://security.ubuntu.com lucid-security Release [44.7kB]
Err http://security.ubuntu.com lucid-security Release
Ign http://in.archive.ubuntu.com/ubuntu/ lucid/universe Translation-en_IN
Ign http://in.archive.ubuntu.com/ubuntu/ lucid/multiverse Translation-en_IN
Get:4 http://in.archive.ubuntu.com lucid-updates Release.gpg [198B]
Ign http://in.archive.ubuntu.com/ubuntu/ lucid-updates/main Translation-en_IN
Ign http://in.archive.ubuntu.com/ubuntu/ lucid-updates/restricted Translation-en_IN
Ign http://in.archive.ubuntu.com/ubuntu/ lucid-updates/universe Translation-en_IN
Ign http://in.archive.ubuntu.com/ubuntu/ lucid-updates/multiverse Translation-en_IN
Hit http://in.archive.ubuntu.com lucid Release
Ign http://in.archive.ubuntu.com lucid Release
Get:5 http://in.archive.ubuntu.com lucid-updates Release [44.7kB]
Err http://in.archive.ubuntu.com lucid-updates Release
Hit http://in.archive.ubuntu.com lucid/main Packages
Hit http://in.archive.ubuntu.com lucid/restricted Packages
Hit http://in.archive.ubuntu.com lucid/main Sources
Hit http://in.archive.ubuntu.com lucid/restricted Sources
Hit http://in.archive.ubuntu.com lucid/universe Packages
Hit http://in.archive.ubuntu.com lucid/universe Sources
Hit http://in.archive.ubuntu.com lucid/multiverse Packages
Hit http://in.archive.ubuntu.com lucid/multiverse Sources
Fetched 587B in 1s (465B/s)
Reading package lists... Done
W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used.GPG error: http://security.ubuntu.com lucid-security Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5
W: GPG error: http://in.archive.ubuntu.com lucid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5
W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used.GPG error: http://in.archive.ubuntu.com lucid-updates Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/lucid-security/Release
W: Failed to fetch http://in.archive.ubuntu.com/ubuntu/dists/lucid-updates/Release
W: Some index files failed to download, they have been ignored, or old ones used instead.
答案1
你需要嘗試：
apt-get install apt-key