how do I copy DVD with basic linux command to get iso no bigger than the original?

I'm trying to copy a SUSE 9 DVD using basic linux commands. The ultimate goal is to modify the DVD content before creating the new image. It works after a fashion except the new .iso is a bit larger than the original, and won't fit back on a DVD.

Where does the bloat come from, and how can I get rid of it?

Here's what I did;

isoinfo -d -i /dev/sr0    # note blocksize and volumesize
dd if=/dev/sr0 bs=blocksize count=volumesize of=foo.iso 
mkdir foo
mount -t iso9660 -o loop foo.iso foo
cp -av foo bar
mkisofs -b boot/loader/isolinux.bin -c boot.cat -boot-info-table -no-emul-boot -r -J -o bar.iso bar

Note that I didn't change anything in bar, yet the bar.iso is bigger than foo.iso, enough so that it won't fit back on a DVD. 'du' shows bar is bigger than foo, but 'diff' shows no differences

du -sk foo bar
4699143 foo
4710654 bar

du -sk foo.iso bar.iso 
3888145 foo.iso
4708322 bar.iso

isoinfo -d -i foo.iso
Volume size is: 1942170

isoinfo -d -i bar.iso
Volume size is: 2351864

CAB

Posted 2012-09-11T16:14:12.390

Reputation: 183

Answers

Be sure to use mkisofs from cdrtools, and not from dvdrtools or cdrkit, the latter contain ancient versions of mkisofs which are slow and produce large ISOs.

See http://cdrecord.berlios.de/private/linux-dist.html

wich

Posted 2012-09-11T16:14:12.390

Reputation: 140

checked using --version as linked article described, and I do have the wrong one. Where do I get the right one? Will it be on the Suse 9.3 install disks? – CAB – 2012-09-12T17:31:37.520

That's very much dependent on the linux distribution, I don't know about Suse, though you can always download the sources and compile yourself. – wich – 2012-09-13T00:35:50.587

We were pressed by lack of time to settle for using a dual layer DVD, which for now, seems to work for us. – CAB – 2012-09-14T12:43:44.880