Ubuntu里，PPA代表一种非稳定版本到发布，喜欢尝试鲜到人一般会加入很多PPA源。
关于PPA到详细说明，可以参考：https://help.launchpad.net/Packaging/PPA
(1).添加一个PPA源 添加一个PPA源：
sudo add-apt-repository ppa:user/ppa-name
如添加cairo-dock到weekly update源：
sudo add-apt-repository ppa:cairo-dock-team/weekly/ubuntu
(2).删除一个PPA源
如果PPA源添加不合适，总会出现update失败的情况，为此要适当时候删除它。
root@ma-ThinkPad-T430:~# cd /etc/apt/sources.list.d
root@ma-ThinkPad-T430:/etc/apt/sources.list.d# ls
apt-build.list
shawn-p-huang-ppa-precise.list apt-build.list.save
shawn-p-huang-ppa-precise.list.save fcitx-team-nightly-precise.list
skunk-pepper-flash-precise.list fcitx-team-nightly-precise.list.save
skunk-pepper-flash-precise.list.save freyja-dev-unity-tweak-tool-daily-precise.list
sogoupinyin.list freyja-dev-unity-tweak-tool-daily-precise.list.save
sogoupinyin.list.save google-chrome.list
starws-box-deadbeef-player-precise.list google-chrome.list.save
starws-box-deadbeef-player-precise.list.save noobslab-deepin-sc-precise.list
ubuntu-desktop-ubuntu-make-precise.list noobslab-deepin-sc-precise.list.save
ubuntuhandbook1-apps-precise.list notepadqq-team-notepadqq-precise.list
ubuntuhandbook1-apps-precise.list.save notepadqq-team-notepadqq-precise.list.save
ubuntu-wine-ppa-precise.list precise-partner.list
ubuntu-wine-ppa-precise.list.save precise-partner.list.save
root@ma-ThinkPad-T430:/etc/apt/sources.list.d# rm -rf ubuntu-desktop-ubuntu-make-precise.list
Ubuntu Kylin 15.04下的PPA源会报404，执行apt-get update卡死：http://www.linuxdiyf.com/linux/12047.html
仅更新指定PPA源的方法：http://www.linuxdiyf.com/linux/9892.html