（仅介绍一点背景信息：我是 Ubuntu 新手，我正在尝试掌握终端并在我的 PC 上安装一些程序。我试图安装媒体播放器 mpv，但首先它要求我确保已安装 git，所以我就在这里。）
我在命令行中输入了 git，它说程序未安装。所以我继续：
$ sudo apt-get install git
然后我得到了这个：
The following extra packages will be installed:
git-man liberror-perl
Suggested packages:
git-daemon-run git-daemon-sysvinit git-doc git-el git-email git-gui gitk
gitweb git-arch git-bzr git-cvs git-svn
The following NEW packages will be installed:
git git-man liberror-perl
0 upgraded, 3 newly installed, 0 to remove and 258 not upgraded.
Do you want to continue [Y/n]?
我同意了，然后它提示我：
WARNING: The following packages cannot be authenticated!
liberror-perl git-man git
Install these packages without verification [y/N]?
如果我输入“n”，它只会退出并显示“E：某些软件包无法验证”。如果我输入“y”，它会显示以下内容：
Err http://br.archive.ubuntu.com/ubuntu/ saucy/main git-man all 1:1.8.3.2-1
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com/ubuntu/ saucy/main git amd64 1:1.8.3.2-1
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Failed to fetch http://br.archive.ubuntu.com/ubuntu/pool/main/g/git/git-man_1.8.3.2-1_all.deb 404 Not Found [IP: 2801:82:80ff:8000::5 80]
Failed to fetch http://br.archive.ubuntu.com/ubuntu/pool/main/g/git/git_1.8.3.2-1_amd64.deb 404 Not Found [IP: 2801:82:80ff:8000::5 80]
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
所以我用“--fix-missing”运行它，但重复所有步骤后它再次退出，这次显示“无法更正丢失的软件包。E：中止安装。”。所以我选择了最后一个选项，即运行：
$ sudo apt-get update
这就是我得到的：
Ign http://br.archive.ubuntu.com saucy InRelease
Ign http://br.archive.ubuntu.com saucy-updates InRelease
Ign http://br.archive.ubuntu.com saucy-backports InRelease
Ign http://br.archive.ubuntu.com saucy Release.gpg
Ign http://br.archive.ubuntu.com saucy-updates Release.gpg
Ign http://br.archive.ubuntu.com saucy-backports Release.gpg
Ign http://br.archive.ubuntu.com saucy Release
Ign http://br.archive.ubuntu.com saucy-updates Release
Ign http://br.archive.ubuntu.com saucy-backports Release
Ign http://br.archive.ubuntu.com saucy/main Sources/DiffIndex
Ign http://br.archive.ubuntu.com saucy/restricted Sources/DiffIndex
Ign http://br.archive.ubuntu.com saucy/universe Sources/DiffIndex
Ign http://br.archive.ubuntu.com saucy/multiverse Sources/DiffIndex
Ign http://br.archive.ubuntu.com saucy/main amd64 Packages/DiffIndex
Ign http://br.archive.ubuntu.com saucy/restricted amd64 Packages/DiffIndex
Ign http://br.archive.ubuntu.com saucy/universe amd64 Packages/DiffIndex
Ign http://br.archive.ubuntu.com saucy/multiverse amd64 Packages/DiffIndex
Ign http://br.archive.ubuntu.com saucy/main i386 Packages/DiffIndex
Ign http://br.archive.ubuntu.com saucy/restricted i386 Packages/DiffIndex
Ign http://linux.dropbox.com precise InRelease
Ign http://br.archive.ubuntu.com saucy/universe i386 Packages/DiffIndex
Ign http://br.archive.ubuntu.com saucy/multiverse i386 Packages/DiffIndex
Hit http://linux.dropbox.com precise Release.gpg
Ign http://security.ubuntu.com saucy-security InRelease
Ign http://br.archive.ubuntu.com saucy-updates/main Sources/DiffIndex
Ign http://br.archive.ubuntu.com saucy-updates/restricted Sources/DiffIndex
Ign http://br.archive.ubuntu.com saucy-updates/universe Sources/DiffIndex
Ign http://br.archive.ubuntu.com saucy-updates/multiverse Sources/DiffIndex
Ign http://br.archive.ubuntu.com saucy-updates/main amd64 Packages/DiffIndex
Hit http://linux.dropbox.com precise Release
Ign http://br.archive.ubuntu.com saucy-updates/restricted amd64 Packages/DiffIndex
Ign http://br.archive.ubuntu.com saucy-updates/universe amd64 Packages/DiffIndex
Ign http://security.ubuntu.com saucy-security Release.gpg
Ign http://br.archive.ubuntu.com saucy-updates/multiverse amd64 Packages/DiffIndex
Ign http://br.archive.ubuntu.com saucy-updates/main i386 Packages/DiffIndex
Ign http://br.archive.ubuntu.com saucy-updates/restricted i386 Packages/DiffIndex
Ign http://br.archive.ubuntu.com saucy-updates/universe i386 Packages/DiffIndex
Ign http://br.archive.ubuntu.com saucy-updates/multiverse i386 Packages/DiffIndex
Hit http://linux.dropbox.com precise/main amd64 Packages
Ign http://security.ubuntu.com saucy-security Release
Ign http://br.archive.ubuntu.com saucy-backports/main Sources/DiffIndex
Ign http://br.archive.ubuntu.com saucy-backports/restricted Sources/DiffIndex
Ign http://br.archive.ubuntu.com saucy-backports/universe Sources/DiffIndex
Ign http://br.archive.ubuntu.com saucy-backports/multiverse Sources/DiffIndex
Ign http://br.archive.ubuntu.com saucy-backports/main amd64 Packages/DiffIndex
Hit http://linux.dropbox.com precise/main i386 Packages
Ign http://br.archive.ubuntu.com saucy-backports/restricted amd64 Packages/DiffIndex
Ign http://br.archive.ubuntu.com saucy-backports/universe amd64 Packages/DiffIndex
Ign http://br.archive.ubuntu.com saucy-backports/multiverse amd64 Packages/DiffIndex
Ign http://br.archive.ubuntu.com saucy-backports/main i386 Packages/DiffIndex
Ign http://br.archive.ubuntu.com saucy-backports/restricted i386 Packages/DiffIndex
Ign http://security.ubuntu.com saucy-security/main Sources/DiffIndex
Ign http://br.archive.ubuntu.com saucy-backports/universe i386 Packages/DiffIndex
Ign http://br.archive.ubuntu.com saucy-backports/multiverse i386 Packages/DiffIndex
Ign http://security.ubuntu.com saucy-security/restricted Sources/DiffIndex
Ign http://security.ubuntu.com saucy-security/universe Sources/DiffIndex
Ign http://security.ubuntu.com saucy-security/multiverse Sources/DiffIndex
Ign http://security.ubuntu.com saucy-security/main amd64 Packages/DiffIndex
Ign http://security.ubuntu.com saucy-security/restricted amd64 Packages/DiffIndex
Ign http://security.ubuntu.com saucy-security/universe amd64 Packages/DiffIndex
Ign http://security.ubuntu.com saucy-security/multiverse amd64 Packages/DiffIndex
Ign http://security.ubuntu.com saucy-security/main i386 Packages/DiffIndex
Ign http://security.ubuntu.com saucy-security/restricted i386 Packages/DiffIndex
Ign http://security.ubuntu.com saucy-security/universe i386 Packages/DiffIndex
Ign http://security.ubuntu.com saucy-security/multiverse i386 Packages/DiffIndex
Ign http://linux.dropbox.com precise/main Translation-en_US
Ign http://linux.dropbox.com precise/main Translation-en
Ign http://br.archive.ubuntu.com saucy/main Translation-en_US
Ign http://br.archive.ubuntu.com saucy/main Translation-en
Ign http://br.archive.ubuntu.com saucy/multiverse Translation-en_US
Ign http://br.archive.ubuntu.com saucy/multiverse Translation-en
Ign http://br.archive.ubuntu.com saucy/restricted Translation-en_US
Ign http://br.archive.ubuntu.com saucy/restricted Translation-en
Ign http://br.archive.ubuntu.com saucy/universe Translation-en_US
Ign http://br.archive.ubuntu.com saucy/universe Translation-en
Ign http://br.archive.ubuntu.com saucy-updates/main Translation-en_US
Ign http://br.archive.ubuntu.com saucy-updates/main Translation-en
Ign http://br.archive.ubuntu.com saucy-updates/multiverse Translation-en_US
Ign http://br.archive.ubuntu.com saucy-updates/multiverse Translation-en
Ign http://br.archive.ubuntu.com saucy-updates/restricted Translation-en_US
Ign http://br.archive.ubuntu.com saucy-updates/restricted Translation-en
Ign http://br.archive.ubuntu.com saucy-updates/universe Translation-en_US
Ign http://br.archive.ubuntu.com saucy-updates/universe Translation-en
Ign http://br.archive.ubuntu.com saucy-backports/main Translation-en_US
Ign http://br.archive.ubuntu.com saucy-backports/main Translation-en
Ign http://br.archive.ubuntu.com saucy-backports/multiverse Translation-en_US
Ign http://br.archive.ubuntu.com saucy-backports/multiverse Translation-en
Ign http://br.archive.ubuntu.com saucy-backports/restricted Translation-en_US
Ign http://br.archive.ubuntu.com saucy-backports/restricted Translation-en
Ign http://br.archive.ubuntu.com saucy-backports/universe Translation-en_US
Ign http://br.archive.ubuntu.com saucy-backports/universe Translation-en
Err http://br.archive.ubuntu.com saucy/main Sources
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy/restricted Sources
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy/universe Sources
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy/multiverse Sources
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy/main amd64 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy/restricted amd64 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy/universe amd64 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy/multiverse amd64 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy/main i386 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy/restricted i386 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy/universe i386 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy/multiverse i386 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-updates/main Sources
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-updates/restricted Sources
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-updates/universe Sources
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-updates/multiverse Sources
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-updates/main amd64 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-updates/restricted amd64 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-updates/universe amd64 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-updates/multiverse amd64 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-updates/main i386 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-updates/restricted i386 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-updates/universe i386 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-updates/multiverse i386 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-backports/main Sources
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-backports/restricted Sources
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-backports/universe Sources
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-backports/multiverse Sources
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-backports/main amd64 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-backports/restricted amd64 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-backports/universe amd64 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-backports/multiverse amd64 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-backports/main i386 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-backports/restricted i386 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-backports/universe i386 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Err http://br.archive.ubuntu.com saucy-backports/multiverse i386 Packages
404 Not Found [IP: 2801:82:80ff:8000::5 80]
Ign http://security.ubuntu.com saucy-security/main Translation-en_US
Ign http://security.ubuntu.com saucy-security/main Translation-en
Ign http://security.ubuntu.com saucy-security/multiverse Translation-en_US
Ign http://security.ubuntu.com saucy-security/multiverse Translation-en
Ign http://security.ubuntu.com saucy-security/restricted Translation-en_US
Ign http://security.ubuntu.com saucy-security/restricted Translation-en
Ign http://security.ubuntu.com saucy-security/universe Translation-en_US
Ign http://security.ubuntu.com saucy-security/universe Translation-en
Err http://security.ubuntu.com saucy-security/main Sources
404 Not Found [IP: 2001:67c:1562::19 80]
Err http://security.ubuntu.com saucy-security/restricted Sources
404 Not Found [IP: 2001:67c:1562::19 80]
Err http://security.ubuntu.com saucy-security/universe Sources
404 Not Found [IP: 2001:67c:1562::19 80]
Err http://security.ubuntu.com saucy-security/multiverse Sources
404 Not Found [IP: 2001:67c:1562::19 80]
Err http://security.ubuntu.com saucy-security/main amd64 Packages
404 Not Found [IP: 2001:67c:1562::19 80]
Err http://security.ubuntu.com saucy-security/restricted amd64 Packages
404 Not Found [IP: 2001:67c:1562::19 80]
Err http://security.ubuntu.com saucy-security/universe amd64 Packages
404 Not Found [IP: 2001:67c:1562::19 80]
Err http://security.ubuntu.com saucy-security/multiverse amd64 Packages
404 Not Found [IP: 2001:67c:1562::19 80]
Err http://security.ubuntu.com saucy-security/main i386 Packages
404 Not Found [IP: 2001:67c:1562::19 80]
Err http://security.ubuntu.com saucy-security/restricted i386 Packages
404 Not Found [IP: 2001:67c:1562::19 80]
Err http://security.ubuntu.com saucy-security/universe i386 Packages
404 Not Found [IP: 2001:67c:1562::19 80]
Err http://security.ubuntu.com saucy-security/multiverse i386 Packages
404 Not Found [IP: 2001:67c:1562::19 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy/main/source/Sources 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy/restricted/source/Sources 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy/universe/source/Sources 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy/multiverse/source/Sources 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy/main/binary-amd64/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy/restricted/binary-amd64/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy/universe/binary-amd64/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy/multiverse/binary-amd64/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy/main/binary-i386/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy/restricted/binary-i386/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy/universe/binary-i386/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy/multiverse/binary-i386/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-updates/main/source/Sources 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-updates/restricted/source/Sources 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-updates/universe/source/Sources 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-updates/multiverse/source/Sources 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-updates/main/binary-amd64/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-updates/restricted/binary-amd64/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-updates/universe/binary-amd64/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-updates/multiverse/binary-amd64/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-updates/main/binary-i386/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-updates/restricted/binary-i386/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-updates/universe/binary-i386/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-updates/multiverse/binary-i386/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-backports/main/source/Sources 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-backports/restricted/source/Sources 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-backports/universe/source/Sources 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-backports/multiverse/source/Sources 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-backports/main/binary-amd64/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-backports/restricted/binary-amd64/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-backports/universe/binary-amd64/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-backports/multiverse/binary-amd64/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-backports/main/binary-i386/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-backports/restricted/binary-i386/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/saucy-security/main/source/Sources 404 Not Found [IP: 2001:67c:1562::19 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-backports/universe/binary-i386/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://br.archive.ubuntu.com/ubuntu/dists/saucy-backports/multiverse/binary-i386/Packages 404 Not Found [IP: 2801:82:80ff:8000::5 80]
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/saucy-security/restricted/source/Sources 404 Not Found [IP: 2001:67c:1562::19 80]
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/saucy-security/universe/source/Sources 404 Not Found [IP: 2001:67c:1562::19 80]
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/saucy-security/multiverse/source/Sources 404 Not Found [IP: 2001:67c:1562::19 80]
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/saucy-security/main/binary-amd64/Packages 404 Not Found [IP: 2001:67c:1562::19 80]
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/saucy-security/restricted/binary-amd64/Packages 404 Not Found [IP: 2001:67c:1562::19 80]
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/saucy-security/universe/binary-amd64/Packages 404 Not Found [IP: 2001:67c:1562::19 80]
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/saucy-security/multiverse/binary-amd64/Packages 404 Not Found [IP: 2001:67c:1562::19 80]
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/saucy-security/main/binary-i386/Packages 404 Not Found [IP: 2001:67c:1562::19 80]
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/saucy-security/restricted/binary-i386/Packages 404 Not Found [IP: 2001:67c:1562::19 80]
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/saucy-security/universe/binary-i386/Packages 404 Not Found [IP: 2001:67c:1562::19 80]
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/saucy-security/multiverse/binary-i386/Packages 404 Not Found [IP: 2001:67c:1562::19 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.
我不知道该如何理解这一切。最后一行是：
E：部分索引文件下载失败。它们已被忽略或使用旧文件代替。
我以为它可能已经成功了，但我重新执行了所有步骤以再次安装 git，但出现了相同的错误，所以显然它不起作用。我很茫然，不知道该怎么做，非常感谢您的帮助，谢谢。
答案1
您正在运行过时的 Ubuntu (saucy) 版本。不再支持其软件包。您需要先升级到最新的受支持的 Ubuntu 版本。
方法如下：如何安装软件或从旧的不受支持的版本升级？（向@JonasCz 致敬）。