I've got an interesting one. I keep track of the md5sums of all the images
I burn. Now, it just so happened that I had deleted an image file that
I later needed. So, I rebuilt a new image via mkisofs from the exact same
directory structure used to create the old image. Now, the two images had
the exact same byte count, but, much to my surprise, they differed with
respect to their md5sums! Why is this?
I used almost the same command line each time:
mkisofs -dvd-video -o image.img directory
The only difference was in the name/path of the output file. I would
expect mkisofs to be deterministic in that the same input data will
produce an identical output result (for the same version of mkisofs,
in my case this is 2.01). Several possibilities for the differing output
files come to mind:
1. mkisofs somehow makes use of a random number generator
2. mkisofs is embedding or using the current time in the output
3. mkisofs is embedding the output filename/path or the command line as
it was invoked within the created image
It would also be good to know if there is a combination of command
line options which will result in identical images with repeated calls
to mkisofs (and if not, maybe this would be a good feature to add to
mkisofs in the future).
Thanks in advance for any info that sheds light on this,
Mike Shell