[[!meta copyright="Copyright © 2026 Free Software Foundation, Inc."]] [[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable id="license" text="Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled [[GNU Free Documentation License|/fdl]]."]]"""]] ISO 9660 is a filesystem that was designed to run on optical disks like CDs or DVDs (but it can run on USB drives as well). Many people will burn an iso image to disk and then install the Hurd via that CD or DVD. `iso9660fs` is how the Hurd reads those images.