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Uploads with ZCB fail with the following error: 

Cloud communication error[CLOUD_ERROR_SignatureDoesNotMatch]

This issue only affects ZCB with Amazon S3. All versions of ZCB with Amazon S3 are affected.

What's going on?

Uploads with ZCB are done in "chunks", and a new connection to Amazon S3 is made each time a new chunk is ready to upload.

Every connection attempt can be routed to a different IP address at Amazon.

Currently, all connections to Amazon endpoints at IP 54.240.235.x are failing. When enough failures happen in a row, ZCB will fail the backup and return the error Cloud communication error[CLOUD_ERROR_SignatureDoesNotMatch].

Update: Feb 3rd, 2014

Zmanda Cloud Backup version 4.10 will include a workaround that will automatically attempt to connect to a new endpoint when uploads attempt to connect endpoints at 54.240.235.X. ZCB 4.10 is expected to release in Q2 2014.

Please continue to use the workaround described below until ZCB 4.10 is released and installed on affected systems.

Amazon has not yet resolved the issues that cause this error.


Until a fix for servers at 54.240.235.x is made at Amazon, we recommend that users force all connections to Amazon to use a known good IP address.

The easiest way to do so is by modifying the hosts file on the machine where ZCB is installed.

Step 1: Open the hosts file

Open the hosts file in Windows XP and 2003

1. Click Start -> All Programs -> Accessories -> Notepad

2. Click File -> Open

3. In the filename field type C:\Windows\System32\Drivers\etc\hosts

4. Click Open

Open the hosts file in Windows Vista and above

 WIndows Vista and above use User Account Control (UAC), so Notepad must be run as Administrator.

1. Click Start -> All Programs -> Accessories

2. Right click Notepad and select Run as administrator

3. Click Continue on the "Windows needs your permission" UAC window.

4. When Notepad opens Click File -> Open

5. In the filename field type C:\Windows\System32\Drivers\etc\hosts

6. Click Open

Step 2: Modify the hosts file

At the bottom of the hosts file, add this line:

Step 3: Save the hosts file

Save the hosts file. This should eliminate the Cloud communication error[CLOUD_ERROR_SignatureDoesNotMatch] error.

We hope that Amazon resolves this issue soon. Once resolved, the changes made to the hosts file should be undone.

Please create a support case if you'd like to be notified when the issue has been resolved.

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