3.2. 记得备份您所有的数据！

Before you start, make sure to back up every file that is now on your system. If this is the first time a non-native operating system is going to be installed on your computer, it is quite likely you will need to re-partition your disk to make room for Debian GNU/Linux. Anytime you partition your disk, you run a risk of losing everything on the disk, no matter what program you use to do it. The programs used in the installation of Debian GNU/Linux are quite reliable and most have seen years of use; but they are also quite powerful and a false move can cost you. Even after backing up, be careful and think about your answers and actions. Two minutes of thinking can save hours of unnecessary work.

如果您是想把计算机做成多重引导的系统，请先把计算机里存在的这些操作系统的安装介质放在手边。即使一般用不上，偶尔也会需要您重新安装操作系统的引导程序(boot loader)使系统可以启动，或者更糟的情况下，得重新安装该操作系统并恢复之前备份的文件。