Comment 15 for bug 475864

I'm still seeing this on 16.04.3. The 'expert_recipe' partitioning string is being skipped / ignored. i.e., anything that looks like this:
---
preseed partman-auto/expert_recipe string \
      boot-root :: \
              500 500 500 ext4 \
                      $primary{ } \
                      $bootable{ } \
                      method{ format } \
                      format{ } \
                      use_filesystem{ } \
                      filesystem{ ext4 } \
                      mountpoint{ /boot } \
              . \
---

Doesn't seem to work. I was very careful, and tried a wide range of options - working on it for several hours with repeated attempts - and it always got skipped. As a result (for me), the automated partitioning stopped at the point where it would clear partitions (as seen in /var/syslog).

I used an approach similar to that provided by Mick Pollard (see above), and it worked as desired.

As an additional note, I used this line to automatically skip a warning about having no swap partition:

preseed --owner partman-basicfilesystems partman-basicfilesystems/no_swap boolean false