1. When installing pihole, choose YES to install admin interface and NO to install lighttpd
2. The snakeoil firmware upgrade process replaces the contents of /var/www, deleting all pihole web admin files (not data)
3. Workaround. Make a copy of /var/www/html somewhere else (home directory)
- after upgrade, copy ~/html back to /var/www
For pihole admin, use the full path http://x.x.x.x/html/admin/index.php
For snakeoil admin use http://x.x.x.x/