* On base system upgrade, move extra packages to base.

* Packages to watch out for (new versions often cause upgrade issues):

  - systemd
  - qemu-system-x86
  - linux-image-amd64
  - g++

  If some of them are very recent (and thus likely to still have issues)
  in unstable, consider using testing. See Debian Changelog for release
  dates.

  Check the current source (unstable/testing) and update if necessary.

* Examining init changes:

  - Get the latest initramfs-tools-core and udev packages.
  - Extract /usr/share/initramfs-tools/{scripts,init} into new directory.
  - Compare:

    diff -urw <old> <new>

    We currently only use init plus udev in scripts/init-{top,bottom}.

* Grep for 'bug' and @@ in init and bootstrap scripts, see if any bugs have
  been fixed and corresponding workarounds can be removed.

  For some may make sense to do a round of cleanups after successful bootstrap
  not to conflate failures.

* Upgrade to latest debootstrap and debian-archive-keyring from unstable
  (or testing).

* Note: as of latest attempt, bootstrap over https was still broken.

* Bootstrap:

  ./bootstrap 2>&1 | tee bootstrap-X.Y.log

  NOTE: tee does not play well with bash prompt (used for troubleshooting).

  NOTE: if during boostrap you need to but unable to delete an intermediate
  btrfs submodules, then it most likely has nested submodules (see nspawn()
  in bootstrap).

  NOTE: to kill nspawn container, press Ctrl-]]].

  Save the log for later comparison (might have to redo a from-stage-1
  bootstrap to get the complete log).

* Compare sizes to previous version for any abnormalities.