Set up a backup with Duplicity & OVH Cloud

Spoiler: As it’s best to do it before it’s too late, we show you how to use duplicity to back up your data to the OVH cloud.

This article updates and replaces the articles “Data backup at OVH with duplicity” and “Recovery of data saved at OVH with duplicity”, obsolete since the switch to version 3 of the Keystone API at OVH on March 24, 2020.

Whether you are an individual or a business, data loss is something to fear. Aside from being unrealistically optimistic, you’ve probably started to think of a way to synchronize your data on a remote system.

And us too, we fear the loss of our data. To prevent this, our important files are first saved on our NAS. This is equipped with hard drives in RAID, to prevent hardware problems. But this does not prevent fires, nor cryptolockers. To do this, we send them every night, in an incremental and encrypted manner, to a server at Gravelines (North of France). How did we do it? This is the subject of our article today.

Thanks to Sylvain S. for proofreading and correcting typos that had crept into the article.

if no precautions are taken, the risk is high. danielschenk @ pixabay

If you followed our previous article that you put it into practice, you should have received an email from OVH. It said that on the 24th march 2020, the Keystone API will be upgrade from 2 to 3 and the v2 will not be available anymore . This article is therefore obsolete, so here is a revised, improved and expanded version of it.

OVH Side

We decided to use the Object Storage from OVH. This is storage space where you pay per space used.

For information, Object Storage is part of the Public Cloud range, which is a professional offer from OVH. You will not be able to order one and obtain it immediately, OVH will ask you for a copy of an identity document before validating the opening of your service.

Once your Public Cloud will be open, you can find it by clicking on Public Cloud, in the bar at the top of the screen of your OVH management interface.

navigation bar

Creating a container

In order to be able to deposit your data, you must first create a container. To do this, click on Object Storage in the menu on the left of the screen.


Then click on Create an object container.

Container Creation

The interface will then ask you to choose the location of your container. Select one not too far from where you live and click on Next.


Choose the type of private container and click Next.Type

Finally, give it a name and click on Create the container.

container name

You can then find your container in the list, in the Storage / Object Storage menu.

Creating a user

Now that you have a container to drop your files into, you need a user to access it.

In the Project Management section, click Users & Roles.


Next, click on «Add user» and give it a description.

The next screen will concern the role of the user being created. In order to be able to determine which role is appropriate, we refer to the matrix of roles provided by OVH. We’re going to use duplicity with the OpenStack / Swift API, so we need to look at the line aboutswift. The only two possible roles are administrator and objectStore operator. As we prefer to use the policy of least privilege, we will therefore be satisfied with ObjectStore operator.


So give the ObjectStore Operator role to your user.


The interface will then show you a password that it is ESSENTIAL to write down (it is not possible to recover a forgotten password, you will then have to regenerate it). Also note in passing the name of your user.


In our case, the user created by OVH is called exgbvthv53G7. And for the smart guys who are wondering, the user was created for example … So no need to try to recover my backups with him …

Retrieving important information

The technology used by OVH for its Cloud system is OpenStack. Usually, the constants needed to use OpenStack can be found in a file named RC. The same goes for OVH.

We will therefore retrieve the OpenStack RC file corresponding to our context via the OVH interface.

To download the file, go to the Project Management / Users & Roles list of users, click on the three small dots to the right of the user you just created, then on Download OpenStack RC File.

Download RC file

Then select the data center (datacenter) where your container is located and click on Download.

Note the following data:

Backup server side

Now that we have done everything we need on the OVH side, we are going to tackle the machine that will send the backups to OVH.

Installing packages

The first thing to do is to install duplicity and the various necessary dependencies.

apt-get update && apt-get install duplicity

Then use pip to install the python modules required by duplicity:

pip install python-swiftclient python-keystoneclient

Key generation

The second step is to generate the keys used for the encryption and for the signature.

ar130405 @ pixabay

Following the recommendations of [RGS v2.0, appendix B2] (, we have therefore created two keys, one for encryption and one for signing.

RuleUsage-1. The use of a key must be unique.


  • Using the same key for more than one purpose, for example to encrypt with a confidentiality mechanism and ensure integrity with a different mechanism, is a source of many errors. However, this does not prevent the derivation of two keys from the same source key provided that the derivation mechanism complies with the repository, nor of setting up an authenticated encryption mechanism where encryption and authentication are provided by a single mechanism. which has been specially designed for such use and not by two separate mechanisms.
  • The use of the same key pair for more than one purpose, for example to encrypt and sign, is also a serious source of errors.

gpg being installed by default onubuntu and debian type systems, in order to generate the keys, we usegpg twice in a row and let ourselves be guided by the key creation tool.

 gpg --full-gen-key

For our part, we have chosen to use 4096-bit keys, because it is recommended by Ubuntu.

In the case of an RSA key, today (2016) it is strongly recommended to use a key with a minimum length of 4096 bits!

See “Primary keys should be DSA-2 or RSA keys, 4096 bits or more (preferably RSA)”or the interview with Phil Zimmermann [de], the inventor of PGP, who in 2013 already recommended a minimum length of 3072 bits for RSA keys.

You can then display your keys with the command.

gpg --list-keys


These are scripts performing backup, listing files, recovering one or all files.

Common base

All of our scripts will require some common information, such as container connection data or key information. To keep things simple, we have chosen to create scripts that we will include in every script that we do.

All of our scripts will start with the same header, containing the different constants for accessing our container. We will therefore create a file containing the following information:

The script:

export SWIFT_USERNAME=<username>
export SWIFT_PASSWORD=<password>
export SWIFT_TENANTNAME=<tenantname>
export =<regionname>

The script is meant to be included, so it doesn’t start with !/Bin/sh

We need to store the keys used for encryption and for signing somewhere, but also the corresponding passphrases. This is because duplicity, in incremental mode, must first retrieve the data from the remote server before it can perform the comparison and determine whether the files are already present on the cloud storage or not. For that, it needs the passphrase of your encryption key to be able to decrypt the data present on the server.

The file contains all the information necessary for using GPG:

The script.

export ENCRYPT_KEY=<clef_chiffrement>
export SIGN_KEY=<clef_signature>
export PASSPHRASE=<passphrase de la clef de chiffrement>
export SIGN_PASSPHRASE=<passphrase de la clef de signature>

This script allows you to send the data you want to backup to your container at OVH.

In order to send the data to the remote server, duplicity is configured to use swift, make incremental backups and copy symbolic links. For the more curious, here is the complete detail of the options passed to duplicity:

The script.

duplicity --full-if-older-than 1M\
                --copy-links \
                --verbosity notice \
                --encrypt-key "$ENCRYPT_KEY" \
                --sign-key "$SIGN_KEY" \
                --num-retries 3 \
                --asynchronous-upload \
                --cf-backend swift \
                --volsize 100 \
                "${1}" "${2}"

In order not to overload the disk and end up with a huge amount of data, going too far back in time, we will use duplicity once again, telling it to delete backups older than 2 months:

The script.

duplicity remove-older-than 2M --force "${1}"

the script

The script ultimately becomes a suite of inclusion of the right scripts, one after the other, preceded by information on the address of the container and the directory containing the data to be backed up:


source $src $dest
source $dest

This script will list all the data you have in your container.

In order to retrieve the list of files present on the remote server, you must use duplicity with thelist-current-files option:

duplicity -t 1D  list-current-files --encrypt-key "$ENCRYPT_KEY"  --sign-key "$SIGN_KEY" --cf-backend swift ${1}

the script

The listing script once again returns to an inclusion list of good scripts, preceded by the address of the OVH container from which you want to retrieve the list of files:


source $src

This script is used to recover all the data contained in your backup container. Be careful, it can take a long time if you have a lot of files.

In order to recover all the files present on the server, you must once again use duplicity:

duplicity -t 1D --encrypt-key "$ENCRYPT_KEY" --sign-key "$SIGN_KEY" --num-retries 3 --cf-backend swift "${1}" "${2}"

the script

In the end, the script will contain information about the container, the path to where the data should be retrieved, as well as the inclusion of all the necessary scripts:


source $src $dest

This script is used to recover a particular file.

duplicity will be used with thefile-to-restore option:

duplicity -t 1D --file-to-restore ${3} --encrypt-key "$ENCRYPT_KEY" --sign-key "$SIGN_KEY" --cf-backend swift ${1} ${2}

the script

The last script that we offer you therefore contains the information necessary to connect to the container, the place where you want to retrieve your data, the file you want to retrieve, then includes all the necessary scripts.


source $src $dest $file

Et après

From now on, as soon as you use these scripts, you can send or retrieve your data from OVH. If you want to automate everything, feel free to use cron.