How to kick off a manual webmin backup job without using the webmin UI:
cd to /etc/webmin/fsdump and issue the following (as root):
# for dump in `grep -l 0\.kitesfear *`; do ./backup.pl `basename $dump .dump`; done
Replace the 0\.kitesfear with whatever unique ID string your backup set is using. Mine uses the format level.hostname, hence a level 0 dump from the server kitesfear is 0.kitesfear (the \ before the dot prevents grep from interpreting . as any single character).