sorry, imho you just have to look harder. how do you search for the string? at least it worked for me (with dummy content), found it with "less" and search for "BSD" and with "strings | grep BSD | head" . Note the strings are filled into fixed width fields in the iso header, i.e. they are no C-strings, no terminators before or after the text (and the standard even seems to require them to be [A-Z0-9_]* for -V and some more characters including space for -A, mkisofs seems to not enforce this..).