Wednesday, 5 June 2019

Re: Supporting LZ4 as initramfs compressor

Hi Dimitri,

One point here:

On Wed, Jun 05, 2019 at 01:15:48PM +0100, Dimitri John Ledkov wrote:
> - lz4 size weight over gzip is marginal (14%) but imho worth the
> improved boot time & initrd creation time

A 14% increase in initramfs size is NOT marginal. Since there are (and will
always be) various scenarios which require a separate /boot partition, we
have over several cycles been contending with how to ensure a clean upgrade
as kernel+initramfs sizes increase over time and push up against the space
limits of the boot partitions that have historically been created.

If you are making a change that increases the size of initramfses by 14%
across the board, you must also:

- update the ubuntu-release-upgrader code to take this into account so
users don't run out of space in the middle of the upgrade
- possibly in a way that is smart enough to know if a user is already
configuring initramfs-tools to use a non-default compressor, to avoid
- check that the minimum size requirements for /boot that are encoded in
the installers are still adequate, or if they need updating (and if they
need updating, update this back to 18.04)
- document this issue in the release notes

Steve Langasek Give me a lever long enough and a Free OS
Debian Developer to set it on, and I can move the world.
Ubuntu Developer