< Features
LZMA for Live Images
Summary
Better compression technology (LZMA) allows us to ship more software on our live images.
Owner
- Name: Bruno Wolff III
- Email: <bruno@wolff.to>
Current status
- Targeted release: Fedora 13
- Last updated: 2009-12-11
- Percentage of completion: 5%
Detailed Description
LZMA compression typically provides better compression than zlib while still providing relatively fast uncompression. Once squashfs file systems are supported by the kernel (which is anticipated in 2.6.33) we can use them for building live images. It is anticipated that there will be savings that are significant for Fedora Live Images. (Once I start testing I'll have a few comparisons.) In particular the Games spin and the Desktop spins may be able to add back some desired packages cut for space reasons.
Benefit to Fedora
By allowing more packages to be put on a Live Image, we can make a few of our space constrained images better. For other images, having them be smaller will make them faster to download.
Scope
- Lougher's patches need to be accepted upstream. This seems likely and we will probably have an answer within two weeks for 2.6.33.
- Lougher's 4.1 (currently prerelease) version of squashfs-tools needs to be in the release.
- livecd-creator needs to be modified to have mksquashfs use lzma compression. (Probably as the default, with other compression methods specifiable as command line options.)
How To Test
- We need to make sure live images work.
- We need to make sure live images are smaller using LZMA compression.
- We need to make sure performance is acceptable. (I.e. that LZMA doesn't slow things down significantly on typical systems.)
User Experience
Live images will be smaller or have more included packages.
Dependencies
- squashfs-tools
- kernel (upstream dependency only)
- livecd-tools
Contingency Plan
- Since the default in the new squashfs is too use zlib compression, we shouldn't have to revert squashfs-tools.
- livecd-creator would need to have at least some of the changes reverted.
Documentation
- Most likely livecd-creator would be getting a new option and would need its help updated along with the code changes.
Release Notes
- Mention the squashfs version change, that it supports LZMA compression, point to its documentation and note that it is supported in the kernel as well.
- Mention that livecd-creator uses LZMA by default, how to get zlib compression if desired for use with older kernels or other reasons.