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Connecting TrueNAS Cloud Sync to Impossible Cloud Storage

This article explains how to configure a TrueNAS Cloud Sync task that pushes data from a TrueNAS dataset to an Impossible Cloud Storage bucket.

Prerequisites

  • TrueNAS 25.10 or later (Community Edition or Enterprise) with at least one pool and dataset containing the data to sync.
  • Correct system time on TrueNAS. Check the timezone and NTP servers under System > General Settings. Clock skew causes S3 signature errors.

Step 1: Create a bucket and access key in the Impossible Cloud Storage Console

Create a target bucket in Impossible Cloud as described in Creating a bucket.

Tip: Create the bucket without versioning and Object Lock. With versioning, overwritten and deleted files remain in the bucket as noncurrent versions and continue to consume storage. With Object Lock, the Sync transfer mode cannot delete locked objects and the task reports errors.

Additonally, we recommend creating a dedicated IAM user and access key for TrueNAS as described in Secure programmatic access to Impossible Cloud Storage. Limit the key to the target bucket. 

Step 2: Add Impossible Cloud as a cloud credential in TrueNAS

  1. Go to Credentials > Backup Credentials and click Add on the Cloud Credentials widget.
  2. Enter a Name, for example impossible-cloud.
  3. Set Provider to Amazon S3.
  4. Enter the Access Key ID and Secret Access Key from Step 1.
  5. Open Advanced Settings and set:
    • Endpoint URL: https://eu-central-2.storage.impossiblecloud.com
    • Region: eu-central-2
    Replace eu-central-2 with the region of your bucket. Endpoint URL and region must match. Leave Disable Endpoint Region and Use Signature Version 2 unchecked.
  6. Click Verify Credential, then Save.

Step 3: Create a Cloud Sync task

    1. Go to Data Protection and click Add on the Cloud Sync Tasks widget. The Cloud Sync Task Wizard opens.
    2. Select the credential from Step 2 and click Next.
    3. Set Direction to Push and select a Transfer Mode:
      • Copy: uploads new and changed files and never deletes objects in the bucket. Objects of files deleted on TrueNAS remain in the bucket.
      • Sync: makes the bucket or prefix identical to the source, including deletions. If the task encounters errors, TrueNAS skips deletions for that run.
      • Move: uploads files and then deletes them from TrueNAS. Use this only for offloading data, not for backup.
    4. First, select the target bucket from the Bucket dropdown. Do this before setting Folder, because the Folder tree only shows the contents of the selected bucket.
    5. Then, in Folder, select / for the bucket root or a prefix such as /truenas. The field must not be empty.
    6. In Directory/Files, expand the tree and select the dataset to sync, for example /mnt/tank/data. Do not select /mnt itself. The path must be inside a pool.
    7. Adjust the Description if needed and set a Schedule.
    8. Under Advanced Options, we recommend:
      • Take Snapshot: enabled, so the task reads from a consistent ZFS snapshot of the dataset.
      • Use --fast-list: enabled, to reduce the number of list requests on large directory trees.
      • Transfers: start with 4 and increase it if bandwidth allows.
    9. Optionally, enable Remote Encryption to encrypt data with rclone crypt before upload. Encrypted data can only be read through TrueNAS or rclone with the same password and salt.
    10. Click Dry Run to test the configuration, then click Save.

    Troubleshooting

    If saving the task fails with attributes.bucket: Field required or attributes.folder: Field required, first select the bucket from the Bucket dropdown, then select the folder in the Folder tree.