Re: Does/can DLB order the disk blocks in the order they are accessed during a default boot?

[intrigeri <intrigeri@debian.org>]

Hi,

Martin Guy (2021-02-23):
> I assume it would be feasible to record the sequence of disk accesses
> during a normal boot from CD/DVD and ensure that the required blocks
> are in the ISO in linear disk-reading order, which should speed boot
> time from optical media.
>
> I guess that means booting the ISO image during the build in something
> virtual, with a magic kernel option to make it spew all the disk
> access addresses, then reorder the ISO accordingly.
>
> Does anyone know if this is already done in live-build, or if any
> other ISO build systems do this?

We do something like this at Tails, using inotify, except:

 - We update the SquashFS ordering as part of our release process,
   not as part of the build.

 - It's not fully automated. Some manual work is required.

 - Nowadays, we optimize for booting from USB drives, not DVD.
   The implementation remained identical though.

For details, look for files called *boot-profile, and "git grep
boot-profile", in our Git repo: https://gitlab.tails.boum.org/tails/tails/

Cheers!