Подготавливаем
./occ app:install user_migration
Экспортируем
for user in $(./occ user:list | awk '{print $2}' | sed 's/://g' | grep -v '^-'); do
mkdir -p "./exported_users/$user/"
chown -R www-data:www-data "./exported_users/$user/"
./occ user:export "$user" "./exported_users/$user/"
done