在ubuntu 10.04服务器上运行apt-get update （输出如下）后，我发现这个问题。 在此之前，我删除了apt-key 。 我在哪里可以得到这个apt-key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.
你需要尝试：
apt-get install apt-key