Pushing backups from TrueNAS to a QNAP NAS with rsync over SSH

Push a one-way copy of data from a TrueNAS system to a QNAP NAS using rsync over SSH with key-based authentication, scheduled as a native TrueNAS rsync transfer task. This is a data-sync mechanism, not a full backup solution on its own — it copies data from A to B but has no versioning or retention of its own.

Prerequisites

• A TrueNAS system (Core or Scale) with shell/SSH access.
• A QNAP NAS with SSH enabled.
• A dataset/share on each side: a source on TrueNAS, a destination share on the QNAP.

Steps

1. Create a destination share on the QNAP

In the QNAP Control Panel → Privilege → Shared Folders, create a shared folder for the backup data (e.g. TNbackup) and restrict its permissions — deny or read-only access for every user except the dedicated rsync user, so nothing else can accidentally modify or delete the backup copy.

2. Create a dedicated user on the QNAP

Create a user (e.g. rsync) and add it to the administrator group — required for SSH access on QNAP — then grant it read/write permissions on the backup share only.

In Control Panel → Users → Advanced Settings, enable home folders for all users. In Control Panel → Network & File Services, enable SSH and SFTP, and set access permissions there if needed.

Verify SSH login works before continuing:

ssh rsync@<qnap-ip>

3. Enable public-key authentication on the QNAP

QNAP ships with public-key auth commented out by default. Edit the sshd config (only vi is available on stock QNAP — no nano):

sudo vi /etc/ssh/sshd_config

Uncomment these two lines:

PubkeyAuthentication yes
AuthorizedKeysFile  .ssh/authorized_keys

Save and exit (:w, then :q), then prepare the key directory in the rsync user’s home folder:

cd /share/homes/rsync/
mkdir .ssh
chmod 024 .ssh
touch .ssh/authorized_keys
sudo chmod -R 025 .ssh
sudo chown -R rsync .ssh

Restart the SSH/rsync services from the QNAP GUI if the settings don’t take effect immediately.

4. Create a matching user and SSH key on TrueNAS

TrueNAS doesn’t create a home directory by default — create one under a dataset first:

cd /mnt/<pool>/
mkdir -p home/rsync

Then create a TrueNAS user (Accounts → Users → Add) with:

Username: rsync
Primary group: rsync
Auxiliary groups: <a group with access to the share(s) to be backed up>
Home directory: /mnt/<pool>/home/rsync

Generate an SSH key pair as that user (accept all defaults):

ssh rsync@<truenas-ip>
ssh-keygen
cat .ssh/id_rsa.pub

Copy the full public key line, then paste it into the TrueNAS user’s SSH Public Key field via the GUI (this also makes it easy to re-add if the key is lost).

5. Authorize the key on the QNAP

Log into the QNAP as the rsync user and paste the same public key into ~/.ssh/authorized_keys:

ssh rsync@<qnap-ip>
vi .ssh/authorized_keys

Test the connection from TrueNAS — it should log in without a password prompt. If it still asks for one, or the connection fails outright, check that the fingerprint TrueNAS recorded in its known_hosts matches the QNAP’s actual host key.

6. Create the rsync transfer task on TrueNAS

In the TrueNAS GUI: Tasks → Rsync Tasks, create a new task:

Setting	Value
Source path	/mnt/<pool>/<share-to-back-up>
User	rsync
Direction	Push
Remote host	<qnap-ip>
Rsync mode	SSH
Remote SSH port	as configured on the QNAP
Remote path	/share/<destination-share>

Disable the compression option — it was found necessary to ensure every file copies correctly. Leave the delete option off unless a true mirror (rather than an accumulating copy) is desired.

Verify

Run the task once manually from the TrueNAS UI and confirm the files appear on the QNAP share. If the task was just created, start a fresh TrueNAS UI/shell session before the first run to avoid stale-session errors.

Troubleshooting

• Passwordless SSH still prompts for a password: re-check PubkeyAuthentication/ AuthorizedKeysFile are uncommented in sshd_config and that .ssh and authorized_keys have the exact permissions above — QNAP’s SSH daemon is strict about directory/file permissions on key files.
• rsync reports corrupted or incomplete files: disable the compression option on the transfer task.
• Host key mismatch: confirm the fingerprint in TrueNAS’s known_hosts matches the QNAP; a QNAP reset or reinstall changes its host key.

Related

Sources

• Legacy wiki.js (de, translated): rsync from TrueNAS to QNAP — private source; German-only wiki.js page, no English original existed
• Original tutorial this page adapts (homeserver.lu, TrueNAS → Synology)