This section explains how to install Debian GNU/Linux from an existing Unix or Linux system, without using the menu-driven installer as explained in the rest of the manual. This “cross-install” HOWTO has been requested by users switching to Debian GNU/Linux from Red Hat, Mandrake, and SUSE. In this section some familiarity with entering *nix commands and navigating the file system is assumed. In this section, $ symbolizes a command to be entered in the user's current system, while # refers to a command entered in the Debian chroot.

Once you've got the new Debian system configured to your preference, you can migrate your existing user data (if any) to it, and keep on rolling. This is therefore a “zero downtime” Debian GNU/Linux install. It's also a clever way for dealing with hardware that otherwise doesn't play friendly with various boot or installation media.