我在进行更新时遇到问题。如果我输入 sudo apt-get update 我将得到以下信息：
Err http://ppa.launchpad.net saucy/main Sources
404 Not Found
Err http://ppa.launchpad.net saucy/main amd64 Packages
404 Not Found
Err http://ppa.launchpad.net saucy/main i386 Packages
404 Not Found
Ign http://packages.linuxmint.com petra/main Translation-en
Ign http://ppa.launchpad.net saucy/main Translation-en_US
Ign http://packages.linuxmint.com petra/upstream Translation-en_US
Ign http://ppa.launchpad.net saucy/main Translation-en
Ign http://ppa.launchpad.net saucy/main Translation-en_US
Ign http://ppa.launchpad.net saucy/main Translation-en
Ign http://ppa.launchpad.net saucy/main Translation-en_US
Ign http://packages.linuxmint.com petra/upstream Translation-en
Ign http://ppa.launchpad.net saucy/main Translation-en
Ign http://ppa.launchpad.net saucy/main Translation-en_US
Ign http://ppa.launchpad.net saucy/main Translation-en
Ign http://ppa.launchpad.net saucy/main Translation-en_US
Ign http://ppa.launchpad.net saucy/main Translation-en
Fetched 204 kB in 9s (21,7 kB/s)
W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/dists/saucy/main/binary-amd64/Packages 404 Not Found
W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/dists/saucy/main/binary-i386/Packages 404 Not Found
W: Failed to fetch http://ppa.launchpad.net/shnatsel/zram/ubuntu/dists/saucy/main/source/Sources 404 Not Found
W: Failed to fetch http://ppa.launchpad.net/shnatsel/zram/ubuntu/dists/saucy/main/binary-amd64/Packages 404 Not Found
W: Failed to fetch http://ppa.launchpad.net/shnatsel/zram/ubuntu/dists/saucy/main/binary-i386/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
inxi -r 的输出是：
Repos: Active apt sources in file: /etc/apt/sources.list
deb http://extras.ubuntu.com/ubuntu/dists/ saucy main
Active apt sources in file: /etc/apt/sources.list.d/additional-repositories.list
deb http://download.virtualbox.org/virtualbox/debian saucy contrib
Active apt sources in file: /etc/apt/sources.list.d/chris-lea-node_js-saucy.list
deb http://ppa.launchpad.net/chris-lea/node.js/ubuntu saucy main
deb-src http://ppa.launchpad.net/chris-lea/node.js/ubuntu saucy main
Active apt sources in file: /etc/apt/sources.list.d/fossfreedom-packagefixes-saucy.list
deb http://ppa.launchpad.net/fossfreedom/packagefixes/ubuntu saucy main
deb-src http://ppa.launchpad.net/fossfreedom/packagefixes/ubuntu saucy main
Active apt sources in file: /etc/apt/sources.list.d/google-talkplugin.list
deb http://dl.google.com/linux/talkplugin/deb/ stable main
Active apt sources in file: /etc/apt/sources.list.d/no1wantdthisname-ppa-saucy.list
deb http://ppa.launchpad.net/no1wantdthisname/ppa/ubuntu saucy main
deb-src http://ppa.launchpad.net/no1wantdthisname/ppa/ubuntu saucy main
Active apt sources in file: /etc/apt/sources.list.d/nviennot-tmate-saucy.list
deb http://ppa.launchpad.net/nviennot/tmate/ubuntu saucy main
deb-src http://ppa.launchpad.net/nviennot/tmate/ubuntu saucy main
Active apt sources in file: /etc/apt/sources.list.d/official-package-repositories.list
deb http://packages.linuxmint.com/ petra main upstream import
deb http://archive.ubuntu.com/ubuntu/ saucy main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ saucy-updates main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu/ saucy-security main restricted universe multiverse
deb http://archive.canonical.com/ubuntu/ saucy partner
Active apt sources in file: /etc/apt/sources.list.d/olivier-berten-misc-saucy.list
deb http://ppa.launchpad.net/olivier-berten/misc/ubuntu saucy main
deb-src http://ppa.launchpad.net/olivier-berten/misc/ubuntu saucy main
Active apt sources in file: /etc/apt/sources.list.d/shnatsel-zram-saucy.list
deb http://ppa.launchpad.net/shnatsel/zram/ubuntu saucy main
deb-src http://ppa.launchpad.net/shnatsel/zram/ubuntu saucy main
Active apt sources in file: /etc/apt/sources.list.d/ubuntu-wine-ppa-saucy.list
deb http://ppa.launchpad.net/ubuntu-wine/ppa/ubuntu saucy main
deb-src http://ppa.launchpad.net/ubuntu-wine/ppa/ubuntu saucy main
Active apt sources in file: /etc/apt/sources.list.d/webupd8team-java-saucy.list
deb http://ppa.launchpad.net/webupd8team/java/ubuntu saucy main
deb-src http://ppa.launchpad.net/webupd8team/java/ubuntu saucy main
Active apt sources in file: /etc/apt/sources.list.d/webupd8team-sublime-text-3-saucy.list
deb http://ppa.launchpad.net/webupd8team/sublime-text-3/ubuntu saucy main
deb-src http://ppa.launchpad.net/webupd8team/sublime-text-3/ubuntu saucy main
Active apt sources in file: /etc/apt/sources.list.d/xorg-edgers-ppa-saucy.list
deb http://ppa.launchpad.net/xorg-edgers/ppa/ubuntu saucy main
deb-src http://ppa.launchpad.net/xorg-edgers/ppa/ubuntu saucy main
我的sources.list仅包含：
deb http://extras.ubuntu.com/ubuntu/dists/ saucy main