Excerpted from mkisofs/README.hide

This document attempts to show how to hide files from being seen by an operating system accessing a CD as an ISO9660/Rock Ridge, Joliet or HFS CD. It also highlights some of the limitations …

Note: this document is about the various -hide options - not be confused with the -hidden options.

The various -hide options actually exclude the relevant directory entry from the directory tree. Therefore, it is not possible to access a file or directory that has be hidden with the -hide option when the ISO9600/Rock Ridge directory is mounted - because the directory entry does not exist on the CD (but the file data does). You would probably be able to access this file or directory when mounted as a Joliet or HFS CD (depending on other options used). Similarly, a directory entry hidden with the -hide-joliet option will not be accessible when mounted as an Joliet CD. Similarly for -hide-hfs etc.

If the file name to be hidden is a directory, then the directory and all its contents are hidden.

The main use of the hide options is on a multi platform (hybrid CD) to hide various files/directories that are operating system specific from been seen on the CD when mounted on another OS. i.e. You may want to hide Macintosh executables from being seen when the CD is mounted as a Joliet CD on a PC etc.

The -hidden options set the 'EXISTENCE' bit in the directory entry which means the file or directory will be invisible - unless some special option is used to mount or view the CD - Linux has the 'unhide' mount option to make these files visible. i.e. the directory entry exists on the CD.