When installing via the hd-media method, there will be a moment where you need to find and mount the Debian Installer iso image in order to get the rest of the installation files. The component iso-scan does exactly this. At first, iso-scan automatically mounts all block devices (e.g. partitions) which have some known filesystem on them and sequentially searches for filenames ending with .iso (or .ISO for that matter). Beware that the first attempt scans only files in the root directory and in the first level of subdirectories (i.e. it finds /whatever.iso, /data/whatever.iso, but not /data/tmp/whatever.iso). After an iso image has been found, iso-scan checks its content to determine if the image is valid Debian iso image or not. In the former case we are done, in the latter iso-scan seeks for another image. In case the previous attempt to find an installer iso image fails, iso-scan will ask you whether you would like to perform more throughly search. This pass doesn't look only into the topmost directories, but really traverses whole filesystem. If iso-scan does not discover your installer iso image, reboot back to your original operating system and check if the image has correct name (ending in .iso), if it is placed on a filesystem recognizable by &d-i;, and if it is not corrupted (verify the checksum). Experienced unix users could do this without rebooting on the second console.