Comment 12 for bug 775124

All I did for my low-disk-space ISO for Lubuntu 11.04 was to edit the file casper/filesystem.size to contain a number lower than the one that was there before. I then edited one line of the file containing md5sums, so that the Test CD Image menu item still works. No change to any code whatsoever was needed, just two text files in the ISO image.

This casper/filesystem.size file is supposed to contain (as a string of ASCII digits) the size in bytes of the filesystem needed for the installation, computed from the installed sizes of all the packages in the default install. What happened, as far as I can tell, is that Ubuntu 11.04 needed a lot of additional working free space, so someone came up with a quick fix and multiplied the value obtained from this file by a "fudge factor" in the ubiquity code. They then tested their change on Ubuntu (and only Ubuntu -- not Xubuntu or Lubuntu), and it worked for Ubuntu, so it was accepted!

In an ideal world, we should revert the "fudge factor" patch in the code, and allow the casper/filesystem.size file to contain the actual size of filesystem needed for a successful installation of whatever flavour of Ubuntu this image is. This is clean, elegant, and easy to understand. Provide the correct data to ubiquity, and it does the right thing.

In practice, I am not sure the Ubuntu folks will want to do that -- the way things are now works fine for them :)

There are many other practical ways to solve this, including code in ubiquity testing which Ubuntu flavour is being used, and setting the "fudge factor" accordingly, which is "ugly" but definitely workable. Other possibilities include a command line option to ubiquity that sets the fudge factor, or one that disables the disk space check, or (trying to avoid too many ugly fudge constants in the code!) looking for an optional file under casper/ that does one of those things and which is then present in Lubuntu ISO images but absent in Ubuntu ones...

In a related bug report (I think it started out satying teh Xubuntu web site had bad info about disk size needs, but was really this issue in disguise), a couple of months ago or more, I offered some time ago to implement one of these ways forward, if someone would tell me it would be accepted, but apparently no-one relevant read it or responded to me about it. Even though my work and real life time constraints are a lot worse now than they were then, that offer stands... I don't have time to discuss all the options, or write formal proposals and try to persuade a group of people to agree on one, etc... but tell me a patch to fix this in any of the ways I mentioned above will be accepted, and I'll happily create that patch and submit a debdiff or a bzr packaging branch containing it.

Jonathan