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Deploy to virtual devices

In this tutorial we will show how to use the intuitive Mender server UI to deploy a full rootfs image update to a virtual device which is connected to the server. The virtual device is bundled with the Mender server to make it easy to test Mender.

A Mender Artifact is a file format that includes metadata like the checksum and name, as well as the actual root file system that is deployed. See Mender Artifacts for a complete description of this format.


The test environment should be set up and working successfully as described in Install a Mender demo server.

Authorize the device

Open the Mender UI in the same browser as you accepted the certificate in as part of Install a Mender demo server. It is available at https://localhost/.

After a minute or two, there should be a virtual device that is waiting authorization. This means that the Mender client, which runs as a daemon on the device, is asking to join the Mender server so that the server can manage its deployments. You can also see these requests in the server access logs in the terminal where you started the Mender server.

You can review the device before authorizing it to join the server. When you are ready, simply click the Authorize button in the Devices tab.

There are security implications to connecting a client and server for the first time, also known as bootstrapping. If a client and server have not exchanged any information in advance, they need to accept each other on trust this first time, with the risk that the information the other party presents is spoofed. To mitigate this risk, the Mender client preinstalls the TLS certificate of the server when it is provisioned, as part of the Yocto Project image build. So it is not possible for a rogue server to intercept the connection from a client or pretend to be a different server, assuming server's private TLS key is securely managed. A rogue device can still spoof the information it sends to the server in order to be authorized, and this is why Mender asks you to make the authorization decision. However, the risk of letting the server manage a rogue device is much lower than the risk of a rogue server managing devices.

See information about the device

Mender automatically collects identity and inventory information about the connected devices. You can view this information by clicking on a device. It should look similar to the following:

Mender UI - Device information

Which information is collected about devices is fully configurable; see the documentation on Identity and Inventory for more information.

After deploying the update below, you can verify that the artifact_name of the virtual device has changed.

The console of the virtual device can be seen by running docker logs $(docker ps | grep mender-client | cut -f1 -d' ').

Upload a new Mender Artifact to the server

First, download the Mender Artifact that can be used with the virtual device.

After the download finishes, go back to the Mender server UI, click the Artifacts tab and upload this Mender Artifact.

All devices report which Device type they are as part of their inventory information, for example vexpress-qemu or beaglebone. In addition, Mender Artifacts have Device types compatible as part of their metadata. During a deployment, Mender makes sure that a device will only get and install an Artifact it is compatible with. This increases the robustness of Mender as it avoids situations like deploying software that is not supported by the device hardware.

Steps to build Artifacts for other device types and with custom software are provided at Building a Mender Yocto Project image.

Deploy the Mender Artifact to the device

Now that we have the device connected and the Artifact uploaded to the server, all that remains is to go to the Deployments tab and click Create a deployment.

You will be asked which Artifact to deploy and which group of devices to deploy it to. Since we have just one Artifact and no custom groups right now, we simply select the Artifact we just uploaded and All devices, then Create deployment.

See the progress of the deployment

As the deployment progresses, you can click on it to view more details about the current status across all devices. In the example below, we can see that the device is in process of installing the Artifact.

Mender UI - Deployment progress

The deployment to the virtual device should take about 2-5 minutes to complete and report success or failure.

Verify the deployment

Once the deployment completes, you should see it in Past deployments. If the deployment fails you can view the deployment log, which is obtained from the device, to diagnose the issue. You can also see the state of deployments on the Dashboard. In Devices you can see that artifact_name has now changed to release-2_1.1.2.

This shows your virtual device runs the new rootfs!

Deploy another update

To deploy another update, first download the second Mender Artifact for the virtual device.

For robustness and avoiding unnecessary deployments, Mender will not deploy an Artifact that is already installed on a device. Thus, if you create another deployment with the Artifact you already uploaded, Mender will see that it contains the same rootfs that is already installed and skip the deployment. It will immediately be marked as successful and moved to Past deployments. This is why we provide a second Artifact for you to test with.

Go to Artifacts again and upload this artifact. After the Artifact has been uploaded, deploy it to your device, using the same steps as before.

Following this, you can deploy the first Artifact again, and so forth.

Deploy to custom groups

As you might have noticed, it is possible to create groups in the Devices tab. Once you have created a group and added one or more devices to it, you can deploy an Artifact to that group by selecting the group instead of All devices when you create a deployment.

This can be very useful in order to deploy to test devices before production, or only deploy to devices owned by a specific customer.

To avoid accidents, Mender only allows a device to be in one group at the time. If a device could be in several groups, for example test and production, unintended deployments and downtime could occur. Therefore, as a safety measure, Mender does not allow this.

Deploy to physical devices

Congratulations! You have used the Mender server to deploy your first managed update! If you have a BeagleBone Black, you can proceed to Deploy to physical devices to try out deploying to a real-world device!