QNAP NAS Error Code 39: How to Fix It

Medium 30-60 minutes Medium Severity Verified June 2026
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Error Code
39
Brand
QNAP
Product Type
nas
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
30-60 minutes
QNAP Error Code 39 indicates that the rsync server connection has been lost during a backup or synchronization job. This typically means your NAS could not maintain a stable connection to the remote rsync server, which can interrupt scheduled backups and data replication tasks. While this is a medium-severity issue that does not immediately threaten your stored data, it should be resolved promptly to ensure your backup jobs complete successfully.
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How to Fix Error Code 39

  1. Check Network Connectivity on Your NAS

    Do not restart the NAS while a backup job is actively running, as this may cause partial data writes or file corruption on the destination.

  2. Verify rsync Server Status and Credentials

  3. Check Firewall Rules on Both Ends

    Opening ports on a public-facing server increases security exposure. Use rsync over SSH (port 22) with key-based authentication rather than plain rsync port 873 for internet-facing transfers.

  4. Restart the rsync Service on the QNAP NAS

    Use SSH with caution — incorrect commands can affect system stability. Only run commands you understand or that are provided by QNAP official documentation.

  5. Update QTS Firmware and Hybrid Backup Sync

    Always back up your NAS configuration (Control Panel > Backup/Restore) before performing a firmware update.

  6. Increase Timeout and Retry Settings in the Backup Job

  7. Test the rsync Connection Manually via SSH

    Do not use /share or critical data folders as your test destination. Use /tmp or a throwaway directory to avoid overwriting important files during testing.
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When to Call a Professional

Contact QNAP technical support or a qualified NAS administrator if: the rsync connection continues to fail after all steps above have been completed; you are unable to SSH into the NAS or the QTS interface is inaccessible; the error is accompanied by other critical alerts such as disk failures or volume degradation; your backup destination is a business-critical server managed by a third party that requires coordination for firewall or service changes; or if the NAS is part of a corporate network with IT security policies that restrict port-level troubleshooting.

Frequently Asked Questions

What does QNAP Error Code 39 mean?
QNAP Error Code 39 means the NAS lost its connection to the rsync server during a backup or sync operation. This can be caused by network instability, incorrect rsync credentials, a firewall blocking port 873 or 22, the rsync service not running on the destination, or a timeout during a large file transfer.
Will Error Code 39 cause me to lose my data?
Error Code 39 itself does not delete or corrupt data already stored on your NAS. It simply means the backup or sync job was interrupted. However, if this error persists and backups are not completing, your backup destination may fall out of date, leaving you without a current copy of your data if a drive failure occurs.
What port does QNAP rsync use and should it be open?
QNAP rsync uses port 873 by default for plain rsync connections. If you configure rsync over SSH, it uses port 22 instead. Port 873 should only be open on your firewall for trusted IP addresses. For internet-facing transfers, rsync over SSH on port 22 with key-based authentication is strongly recommended for security.
How do I restart the rsync service on a QNAP NAS?
You can restart the rsync service by SSH-ing into your QNAP NAS and running the command '/etc/init.d/rsyncd.sh restart'. Alternatively, restarting the Hybrid Backup Sync application from the QTS App Center will also reinitialize rsync-related services without requiring a full NAS reboot.
Can a slow or unstable internet connection cause QNAP Error Code 39?
Yes. If you are syncing to a remote server over the internet and your connection is slow or drops intermittently, rsync may time out and return Error Code 39. To reduce this risk, increase the connection timeout setting in your backup job, schedule backups during off-peak hours, and consider using a wired Ethernet connection on your NAS instead of Wi-Fi.

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