当我输入时，sudo apt-get update我得到了这个：
mohd-arafat-hossain@TUD:~$ sudo apt-get update
[sudo] password for mohd-arafat-hossain:
Ign http://bd.archive.ubuntu.com precise InRelease
Ign http://bd.archive.ubuntu.com precise-updates InRelease
Ign http://bd.archive.ubuntu.com precise-backports InRelease
Ign http://bd.archive.ubuntu.com precise Release.gpg
Ign http://bd.archive.ubuntu.com precise-updates Release.gpg
Ign http://bd.archive.ubuntu.com precise-backports Release.gpg
Ign http://bd.archive.ubuntu.com precise Release
Ign http://bd.archive.ubuntu.com precise-updates Release
Ign http://bd.archive.ubuntu.com precise-backports Release
Ign http://extras.ubuntu.com precise InRelease
Ign http://ppa.launchpad.net precise InRelease
Hit http://extras.ubuntu.com precise Release.gpg
Hit http://ppa.launchpad.net precise Release.gpg
Hit http://extras.ubuntu.com precise Release
Hit http://ppa.launchpad.net precise Release
Hit http://extras.ubuntu.com precise/main Sources
Hit http://bd.archive.ubuntu.com precise/main TranslationIndex
Hit http://ppa.launchpad.net precise/main Sources
Hit http://bd.archive.ubuntu.com precise/multiverse TranslationIndex
Hit http://bd.archive.ubuntu.com precise/restricted TranslationIndex
Hit http://extras.ubuntu.com precise/main i386 Packages
Ign http://extras.ubuntu.com precise/main TranslationIndex
Hit http://bd.archive.ubuntu.com precise/universe TranslationIndex
Hit http://ppa.launchpad.net precise/main i386 Packages
Ign http://ppa.launchpad.net precise/main TranslationIndex
Ign http://security.ubuntu.com precise-security InRelease
Hit http://security.ubuntu.com precise-security Release.gpg
Hit http://bd.archive.ubuntu.com precise-updates/main TranslationIndex
Hit http://security.ubuntu.com precise-security Release
Hit http://bd.archive.ubuntu.com precise-updates/multiverse TranslationIndex
Hit http://bd.archive.ubuntu.com precise-updates/restricted TranslationIndex
Hit http://bd.archive.ubuntu.com precise-updates/universe TranslationIndex
Hit http://security.ubuntu.com precise-security/main Sources
Ign http://extras.ubuntu.com precise/main Translation-en_US
Ign http://ppa.launchpad.net precise/main Translation-en_US
Ign http://extras.ubuntu.com precise/main Translation-en
Hit http://bd.archive.ubuntu.com precise-backports/main TranslationIndex
Hit http://bd.archive.ubuntu.com precise-backports/multiverse TranslationIndex
Hit http://bd.archive.ubuntu.com precise-backports/restricted TranslationIndex
Ign http://ppa.launchpad.net precise/main Translation-en
Hit http://bd.archive.ubuntu.com precise-backports/universe TranslationIndex
Hit http://bd.archive.ubuntu.com precise/main Translation-en
Hit http://bd.archive.ubuntu.com precise/multiverse Translation-en
Hit http://bd.archive.ubuntu.com precise/restricted Translation-en
Hit http://bd.archive.ubuntu.com precise/universe Translation-en
Hit http://security.ubuntu.com precise-security/restricted Sources
Hit http://security.ubuntu.com precise-security/universe Sources
Hit http://security.ubuntu.com precise-security/multiverse Sources
Hit http://security.ubuntu.com precise-security/main i386 Packages
Hit http://security.ubuntu.com precise-security/restricted i386 Packages
Hit http://bd.archive.ubuntu.com precise-updates/main Translation-en
Hit http://bd.archive.ubuntu.com precise-updates/multiverse Translation-en
Hit http://security.ubuntu.com precise-security/universe i386 Packages
Hit http://security.ubuntu.com precise-security/multiverse i386 Packages
Hit http://security.ubuntu.com precise-security/main TranslationIndex
Hit http://security.ubuntu.com precise-security/multiverse TranslationIndex
Hit http://security.ubuntu.com precise-security/restricted TranslationIndex
Hit http://security.ubuntu.com precise-security/universe TranslationIndex
Hit http://bd.archive.ubuntu.com precise-updates/restricted Translation-en
Hit http://bd.archive.ubuntu.com precise-updates/universe Translation-en
Hit http://security.ubuntu.com precise-security/main Translation-en
Hit http://security.ubuntu.com precise-security/multiverse Translation-en
Hit http://security.ubuntu.com precise-security/restricted Translation-en
Hit http://security.ubuntu.com precise-security/universe Translation-en
Hit http://bd.archive.ubuntu.com precise-backports/main Translation-en
Hit http://bd.archive.ubuntu.com precise-backports/multiverse Translation-en
Hit http://bd.archive.ubuntu.com precise-backports/restricted Translation-en
Hit http://bd.archive.ubuntu.com precise-backports/universe Translation-en
Err http://bd.archive.ubuntu.com precise/main Sources
404 Not Found
Err http://bd.archive.ubuntu.com precise/restricted Sources
404 Not Found
Err http://bd.archive.ubuntu.com precise/universe Sources
404 Not Found
Err http://bd.archive.ubuntu.com precise/multiverse Sources
404 Not Found
Err http://bd.archive.ubuntu.com precise/main i386 Packages
404 Not Found
Err http://bd.archive.ubuntu.com precise/restricted i386 Packages
404 Not Found
Err http://bd.archive.ubuntu.com precise/universe i386 Packages
404 Not Found
Err http://bd.archive.ubuntu.com precise/multiverse i386 Packages
404 Not Found
Err http://bd.archive.ubuntu.com precise-updates/main Sources
404 Not Found
Err http://bd.archive.ubuntu.com precise-updates/restricted Sources
404 Not Found
Err http://bd.archive.ubuntu.com precise-updates/universe Sources
404 Not Found
Err http://bd.archive.ubuntu.com precise-updates/multiverse Sources
404 Not Found
Err http://bd.archive.ubuntu.com precise-updates/main i386 Packages
404 Not Found
Err http://bd.archive.ubuntu.com precise-updates/restricted i386 Packages
404 Not Found
Err http://bd.archive.ubuntu.com precise-updates/universe i386 Packages
404 Not Found
Err http://bd.archive.ubuntu.com precise-updates/multiverse i386 Packages
404 Not Found
Err http://bd.archive.ubuntu.com precise-backports/main Sources
404 Not Found
Err http://bd.archive.ubuntu.com precise-backports/restricted Sources
404 Not Found
Err http://bd.archive.ubuntu.com precise-backports/universe Sources
404 Not Found
Err http://bd.archive.ubuntu.com precise-backports/multiverse Sources
404 Not Found
Err http://bd.archive.ubuntu.com precise-backports/main i386 Packages
404 Not Found
Err http://bd.archive.ubuntu.com precise-backports/restricted i386 Packages
404 Not Found
Err http://bd.archive.ubuntu.com precise-backports/universe i386 Packages
404 Not Found
Err http://bd.archive.ubuntu.com precise-backports/multiverse i386 Packages
404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise/main/source/Sources 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise/restricted/source/Sources 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise/universe/source/Sources 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise/multiverse/source/Sources 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise/main/binary-i386/Packages 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise/restricted/binary-i386/Packages 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise/universe/binary-i386/Packages 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise/multiverse/binary-i386/Packages 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise-updates/main/source/Sources 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise-updates/restricted/source/Sources 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise-updates/universe/source/Sources 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise-updates/multiverse/source/Sources 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise-updates/main/binary-i386/Packages 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise-updates/restricted/binary-i386/Packages 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise-updates/universe/binary-i386/Packages 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise-updates/multiverse/binary-i386/Packages 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise-backports/main/source/Sources 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise-backports/restricted/source/Sources 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise-backports/universe/source/Sources 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise-backports/multiverse/source/Sources 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise-backports/main/binary-i386/Packages 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise-backports/restricted/binary-i386/Packages 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise-backports/universe/binary-i386/Packages 404 Not Found
W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/precise-backports/multiverse/binary-i386/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
如何解决此问题且不出现此错误？请
答案1
正在观看https://launchpad.net/ubuntu/+mirror/mirrors.ispros.com.bd-archive，看来孟加拉国镜像还没有更新 Precise 软件包。你可能需要选择附近的其他镜像（我想到的是印度）或者提交有关它的错误。
答案2
每当我更新 Ubuntu 12.04 软件包时，我总是尝试确保从最近/最好的镜像/服务器下载它们。
首先启动软件中心。
从菜单栏中选择编辑，然后选择软件源。...
- 单击下载自选项的下拉箭头。
- 选择其他。
- 点击“选择最佳服务器”。
- 软件中心现在将执行一系列测试来找到最适合您所在位置的镜像。
来源：http://www.ubuntulinuxguide.com/sudo-apt-get-update-error-slow-mirror-ubuntu-12-04/
答案3
您收到的错误是因为链接实际上已被删除。这可能是暂时的，也可能是服务器无法正常工作或正在维护。（在您的情况下，包文件尚未上传到服务器）
要解决这个问题，您可以尝试更改下载源（这可能有效也可能无效，具体取决于服务器）
打开software sources
单击ubuntu software选项卡
，然后Download from选择其他，然后单击select best server
之后软件源将自动更新。