Are you trying to finally get rid of your old laptop, but don’t know if it contains still some data that might be relevant some day? If it still runs, just boot it up with a recent Knoppix boot medium and backup its data.
The default settings of mkisofs can’t handle deeply nested paths well, so I suggest the following parameters:
mkisofs -input-charset iso8859-1 -iso-level 4 -udf -o /path/to/destination.iso -V your_volume_label /directory/to/backup
Note: For easy handling of the data in OSX, you should copy the ISO file to a backup disk that’s formatted with exFAT filesystem.