原来一直用tar、sync等软件实现备份。需要些脚本还要找一台其他服务器进行同步。现在有了DROPBOX这个网站提供的服务，一切都变容易了。
DROPBOX网站：
DROP功能：
偷懒直接把官方介绍帖过来了。主要就是免费提供2G的同步空间，可以自动同步文件并保留文件的历史版本
Dropbox Features
File Sync
Dropbox allows you to sync your files online and across your computers automatically.
- 2GB of online storage for free, with up to 100GB available to paying customers.
- Sync files of any size or type.
- Sync Windows, Mac and Linux computers.
- Automatically syncs when new files or changes are detected.
- Work on files in your Dropbox even if you're offline. Your changes sync once your computer has an Internet connection again.
- Dropbox transfers will correctly resume where they left off if the connection drops.
- Efficient sync - only the pieces of a file that changed (not the whole file) are synced. This saves you time.
- Doesn't hog your Internet connection. You can manually set bandwidth limits.
