buildd cloud-images used by Multipass/Snapcraft do not clear /var/lib/dbus/machine-id

most images using livecd-rootfs include udev, dbus, and a kernel of some sort during the bootstrap phase. Turns out, as a step during the lb_config phase, a series of cleanup actions are taken:

https://git.launchpad.net/livecd-rootfs/tree/live-build/auto/config#n1128

add_chroot_hook update-apt-file-cache
add_chroot_hook update-apt-xapian-index
add_chroot_hook update-mlocate-database
add_chroot_hook remove-dbus-machine-id
add_chroot_hook remove-openssh-server-host-keys
add_chroot_hook remove-udev-persistent-rules

These hooks exist in upstream live-build, which Ubuntu syncs source:

https://git.launchpad.net/~live-build/live-build/tree/share/hooks/normal

These steps are run after lb_bootstrap during lb_config, before lb_hooks. buildd is a special beast, as its seeds do not contain udev , dbus, or a kernel. buildd was originally designed to run in a container, and didn’t have requirements for those items. however, Bootable Buildd, as a virtual machine, installs them during a the build hook

https://git.launchpad.net/livecd-rootfs/tree/live-build/buildd/hooks/52-linux-virtual-image.binary#n51

What ends up happening is the cleanup of /var/lib/dbus/machine never occurs in buildd. and that’s a problem.

We should also check the other cleanup scripts in referenced in livecd-rootfs, pull from live-build. They may be causing other issues with the bootable buildd images.

Also added launchpad-buildd to ensure that removing machine-id will not affect launchpad builders

$ readlink /var/lib/dbus/machine-id
/etc/machine-id

The correct ubuntu implementation should be that dbus machine-id is a symlink to /etc/machine-id. and that /etc/machine-id on the golden image exists, but is an empty file.

This is the case for all our other preinstalled images. This ideally should be universally checked and we must never produce any preinstalled images that have anything else but that.