# Looking for the &debian; Installer ISO Image

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 and logical volumes) 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 a 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 a more thorough search. This pass doesn't just look 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 is named correctly (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.

Note that the partition (or disk) hosting the ISO image can't be reused during the installation process as it will be in use by the installer. To work-around this, and provided that you have enough system memory, the installer can copy the ISO image into RAM before mounting it. This is controlled by the low priority `iso-scan/copy_iso_to_ram` debconf question (it is only asked if the memory requirement is met).