Comment 0 for bug 2039209

Our last respin of the Ubuntu Desktop ISO for mantic to pick up a new version of the ubuntu-desktop-installer snap also unexpectedly increased the total image size by 50MiB.

Tracked this down to the addition of a new file under /var/cache:

$ du -sh /mnt/*/var/cache/swcatalog/cache/C-os-catalog.xb
8.4M /mnt/2/var/cache/swcatalog/cache/C-os-catalog.xb
$

This file gets compressed, but we get a SEPARATE copy of it in each of the per-language squashfs layers on the system.

Previously, this file WAS present in the minimal.enhanced-secureboot.squashfs, however something has changed to cause this file to be different in each of the per-language layers on top of this.

A copy also ended up in casper/minimal.standard.live.squashfs that had not been there before.

I think the image builds should enforce a whitelist of files allowed under /var/cache and fail the build for unexpected contents for each given squashfs layer.