Will Ubuntu use lzm2 or xz compression to save space on the CD?

Question

when ubuntu will use lzma2 compression by default to save cd space. Opensuse 11.4 is doing it by default.

Answer 1

Some packages are already compressed using xz, and there is increasing support for this in the tools. While this improves the space situation for the alternate images, live and preinstalled images are distributed with the packages unpacked, and so do not benefit from this.

Live images are unlikely to be converted to use xz anytime soon, as the current squashfs-lzma breaks rsync/zsync, significantly raising the bandwidth requirements for mirroring the image archives. If this is confirmed as fixed, there is likely great interest in switching, as there is never enough space for everything desired on a CD.

Preinstall images are unlikely to be converted to use xz in the short term, due to relative unfamiliarity and a desire to support a wide range of intermediate environments used to convert the distributed image to an on-disc format.

Answer 2

Well, Ubuntu (at least 10.10) uses SquashFS on the root filesystem (the filesystem that gets mounted when one boots) located in /casper/filesystem.squashfs.