Many of our images have a lot of empty space in them. There are projects around that take advantage of sparse files and filemaps to create a better image writer which only writes the necessary data to the target device. This should result in smaller images and faster device write times (and longer flash life as well).
Tom is going to try and find the MeeGo solution reference...
So the bare filesystem images are sparse already: $ du -h core-image-sato-nuc-20140916184231.rootfs.ext3 444M core-image-sato-nuc-20140916184231.rootfs.ext3 $ du -h --apparent-size core-image-sato-nuc-20140916184231.rootfs.ext3 984M core-image-sato-nuc-20140916184231.rootfs.ext3 But when that gets wrapped up into a hddimg most of the sparseness disappears: $ du -h core-image-sato-nuc-20140916184231.hddimg 1000M core-image-sato-nuc-20140916184231.hddimg $ du -h --apparent-size core-image-sato-nuc-20140916184231.hddimg 1014M core-image-sato-nuc-20140916184231.hddimg
*Most*, this is due to wrapping an ext in a fat in a... and it's filesystems all the way down. There's a problem with wic in that it *doesn't* do sparse, but there's a patch for that already.