For `dokku/dokku-postgres`. See https://gist.github.com/henrik/26bb73091712aa42abf2#db-backups for setup instructions.

dokku_postgres_backups.sh

#!/bin/bash
# For use with dokku/dokku-postgres.
# Based on https://gist.github.com/henrik/1043fecdd0937034cd62

set -e

base_dir="/var/backups/postgres"
mkdir -p $base_dir

ymd=$(date "+%Y-%m-%d")

for db_name in `dokku postgres:list | sed 1d | awk '{print $1}'`
do
  file="$base_dir/$ymd-$db_name.dump"
  dokku postgres:export $db_name > "$file"
done

# delete backup files older than 10 days
# (since Digital Ocean disk backups can be as infrequent as every 7 days)
old=$(find $base_dir -mtime +10)
if [ -n "$old" ] ; then
  echo deleting old backup files: $old
  echo $old | xargs rm -rfv
fi