Thursday 27 December 2018

k3b, mkisofs, and hard linked files

As it's the end of the year, I decided to back up photos from my trips onto DVD. A du -sh of the directories showed that they would fit onto a standard DVD. But when I went to create the image in k3b, it wanted a double layer DVD.

I knew what the problem was, in those albums I had made heavy use of hard links to provide multiple access paths to photos without using extra disk space.

Checking the man page of mkisofs showed that there were a pair of options, --cache-inodes and the negative form. I added this option to the arguments passed by k3b to mkisofs and bingo, the space of the image halved, even though the preview claimed that it required almost 8GiB of DVD.

Looking at the verbose output of k3b on the terminal showed that --no-cache-inodes is the default, presumably to avoid problems with dumping filesystems that don't have working inodes.

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