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 has been installed on your computer, it's 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 installation 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.

如果您想把電腦做成多重開機的系統，請先確定您手頭上有電腦裡已存在的作業系統的安裝媒介。特別是當您把開機磁碟重新分割以後，您可能會發現必須重新安裝原有作業系統的 boot-loader，某些情況下，還得重新安裝該作業系統並恢復受影響分割區上的檔案。