Synology Dropbox Backup: 3 Ways to Do It

Synology Dropbox backup means copying files from your Dropbox account to a Synology NAS, either on a schedule or manually. You can do it with the built-in Cloud Sync app, with Synology Drive Client on a computer, or with a third-party tool like rclone. This article explains each method, how to pick one, and what to watch out for.

What Cloud Sync Does

Cloud Sync is the app Synology provides for connecting your NAS to public cloud services. It links a Dropbox folder to a shared folder on the NAS and then syncs changes in both directions, or one direction if you prefer. Once the link is set up, you can treat the NAS folder like any other shared folder: access it over the local network, back it up with Hyper Backup, or share it with other users.

Cloud Sync supports two sync modes:

• Two-way sync – changes in Dropbox and on the NAS are mirrored. Delete a file in Dropbox and it is deleted on the NAS; edit a file on the NAS and the change is uploaded.
• One-way sync – you choose the source and the destination. For backup, you would set Dropbox as the source and the NAS as the destination, so files only flow from Dropbox to the NAS.

For a true backup, one-way sync from Dropbox to the NAS is the safer choice. Two-way sync is convenient, but it also propagates accidental deletions and ransomware encryption from either side.

Setting Up Cloud Sync

The process takes about five minutes if you already have a Dropbox account and a Synology NAS with DSM 7 installed.

1. Open Package Center on your Synology and install Cloud Sync.
2. Launch Cloud Sync and click + to add a new sync task.
3. Select Dropbox from the list of cloud providers.
4. Click Authorize – a browser window opens asking you to log in to Dropbox and grant Synology access.
5. Choose the Dropbox folder you want to sync (the whole account or a subfolder).
6. Choose the local NAS folder where the files should land.
7. Pick the sync direction (one-way or two-way) and set a schedule if you do not want continuous syncing.
8. Click Apply. Cloud Sync will scan the Dropbox folder and start transferring files.

After the first sync, Cloud Sync keeps watching for changes. It uses Dropbox’s API, so it does not need a computer to be running. The NAS does the work on its own.

Synology Drive Client as an Alternative

If you do not want to give Dropbox API access to your NAS, you can use Synology Drive Client on a Windows or macOS computer. This is a desktop app that syncs a local folder to your Synology NAS. The workflow is:

1. Install the Synology Drive Server package on the NAS.
2. Install Synology Drive Client on your computer.
3. In Drive Client, create a sync task between a local folder and a NAS folder.
4. Point Dropbox’s desktop app at the same local folder (or a subfolder of it).

Dropbox syncs to the local folder, and Drive Client syncs that folder to the NAS. This gives you a local copy plus a NAS copy, but it only works while the computer is on and logged in. It also uses double the local disk space because the files exist in both the Dropbox cache and the Drive Client folder.

Using rclone for Advanced Users

rclone is a command-line program that can copy files between many storage systems, including Dropbox and any local folder. It runs on the Synology NAS if you install it via the community package or a Docker container. The basic idea is to run a scheduled task that copies new or changed files from Dropbox to a NAS folder.

A typical rclone command looks like:

rclone copy dropbox: /volume1/backup/dropbox --transfers 4

You would put that in a Task Scheduler script on the NAS to run nightly. rclone gives you more control over bandwidth, file filtering, and encryption than Cloud Sync, but it requires comfort with the command line and reading its documentation.

Which Method Should You Choose?

The right method depends on how much control you want and whether you need a live mirror or a snapshot-style backup.

• Cloud Sync – best for most people. It is built into DSM, has a graphical interface, and keeps the NAS copy continuously up to date.
• Drive Client – best if you already use Dropbox on a desktop and want a second copy without giving Dropbox API access to the NAS. It requires the computer to be running.
• rclone – best for users who want scheduled, one-way copies with custom filtering, or who prefer open-source tools. It is more work to set up.

For a pure backup, one-way sync with Cloud Sync or a scheduled rclone copy is the most reliable. Two-way sync is not a backup strategy because deletions and corruption can propagate.

Common Problems and How to Fix Them

People run into a few recurring issues when backing up Dropbox to a Synology NAS.

• Files are not appearing on the NAS – check that the sync task is running. Go to Cloud Sync, select the task, and look at the log. If the task is paused, resume it. Also verify that the Dropbox folder you selected actually contains files.
• Sync is very slow – Dropbox API rate limits can slow down large initial syncs. You can set a bandwidth limit in Cloud Sync, but the bottleneck is often Dropbox’s server side. Large folders with many small files take longer than a few large files.
• File names with special characters – Dropbox allows some characters that the NAS file system does not (like a colon on Windows). Cloud Sync renames these files automatically, which can confuse you later. Check the rename log if you see odd names.
• Deleted files on Dropbox are deleted on the NAS – that is expected in two-way sync. If you want to keep them, enable the Recycle Bin on the NAS shared folder. Then deleted files go to the recycle bin instead of being erased.
• Cloud Sync keeps asking to reauthorize – Dropbox tokens can expire. Reconnect the account in Cloud Sync settings.

Costs and Limitations

Synology Cloud Sync is free with DSM. Dropbox has a free tier (2 GB) and paid plans with more storage. The NAS itself is a one-time hardware cost, plus electricity and drive replacement over time. There is no per-GB fee for the NAS copy.

Limitations to know:

• Dropbox’s API has rate limits, so very large syncs can take days.
• Cloud Sync does not keep version history. If a file is overwritten in Dropbox, the NAS copy is overwritten too. Use Synology Snapshot Replication on the NAS folder to keep point-in-time versions.
• Dropbox Business accounts may have different API permissions. If you cannot authorize, check with your workspace admin.

Frequently Asked Questions

Does Cloud Sync count against my Dropbox storage?

No. Cloud Sync downloads files from Dropbox to the NAS. It does not upload anything unless you set up two-way sync and add files to the NAS folder. The storage used on Dropbox is whatever you already have there.

Can I back up multiple Dropbox accounts to one NAS?

Yes. In Cloud Sync, create a separate sync task for each Dropbox account. Each task needs its own authorization and its own local folder.

Is Cloud Sync a real backup?

It is a copy, but not a complete backup by itself. If Dropbox deletes files, those deletions are mirrored to the NAS in two-way sync. For a true backup, use one-way sync and enable the recycle bin or snapshots on the NAS folder.

What happens if the NAS is off during a scheduled sync?

Cloud Sync runs on the NAS, so if the NAS is off, the sync simply does not happen. When the NAS turns back on, Cloud Sync will catch up and sync any changes that occurred while it was offline.

Can I access the Dropbox files on the NAS without an internet connection?

Yes. Once files are copied to the NAS, they are local files. You can access them over your local network even if the internet is down. That is one of the main benefits of backing up Dropbox to a NAS.

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