08 Aero Network and System Administration

Networking: Access Point Wifi

Please refer to the module C2 - Lab Setup - Network and ssh of the course for more details. Here are the basic facts:

By default, Intel's Yocto for Aero is broadcasting a WiFi access point called Aero-<MAC> and Wi-Fi password is 1234567890.

The IP of Aero is 192.168.8.1. Login is root, no password.

Launch a terminal and connect to aero via SSH as follows:

ssh [email protected]

After connecting to Aero it's advised to change the passkey and ssid by using the following commands:

# nmcli c modify hotspot 802-11-wireless-security.psk <new passkey>
# nmcli c modify hotspot 802-11-wireless.ssid <new ssid>

Need to restart NetworkManager with below command to take effect of new SSID

# systemctl restart NetworkManager

You can also edit the configuration file in /etc/NetworkManager/system-connections/hotspot.

On macOS and Linux it's possible to use the link-local name rather than fixed IP. Refer to the documentation of your distro on how to enable it; it's enabled by default on Fedora and Archlinux's documentation works on several Linux distributions and macOS:

ssh [email protected]

Networking: Internet Access

Please refer to the module C2 - Lab Setup - Network and ssh of the course for more details. Here are the basic facts:

In order to have internet access on Aero board it's possible to switch it to client mode so it connects to your Access Point instead of being an Access Point itself. We'll use the standard connman.

Here's the procedure:

For 1.5 or newer release:

First you need to disable AP mode which is the default one:

# nmcli c down hotspot
Connection 'hotspot' successfully deactivated (D-Bus active path: ...
# nmcli c modify hotspot connection.autoconnect no

Scan WiFi networks with nmcli dev wifi command. Example:

# nmcli dev wifi
   ABCD-C072-5         Infra  157   54 Mbit/s  79      ***   WPA1 WPA2
   MYOFFICEWLAN        Infra  44    54 Mbit/s  75      ***   WPA1 WPA2 802.1X 
   LabWLAN             Infra  44    54 Mbit/s  75      ***   WPA2 802.1X
   AndroidHotspot      Infra  44    54 Mbit/s  74      ***   WPA2 802.1X
   OfficeWLAN2         Infra  1     54 Mbit/s  74      ***   WPA2 802.1X

Connect to one network by giving the desired ssid and passkey. From the example above we can connect to ABCD-C072-5 with:

nmcli dev wifi connect ABCD-C072-5 password 12mysecretpassword34

With this configuration it will try to autoconnect to this network every time you boot Intel Aero board.

For 1.4 release:

• Log in as the default root user on the drone;
• Run the application connmanctl, you will enter the connmanctl CLI which will be presented with the connmanctl> prompt;
• If you run the command technologies, it should display WiFi as being Powered and Tethering (AP mode) as True;
• Disable AP mode by running: tether wifi off
• Enable the agent to allow typing a password: agent on
• Scan for existing WiFi connections by running: scan wifi
• After it shows scan as completed, list the connections found by running: services
• Choose which connection you want to use and take a look at the second field there, the connection id, you will use it on the next command (and remember you can use tab completion so you don't have to type everything, or better just to copy and paste the connection id on the command below);
• Run the command: connect wifi_< connection id >​, in which < connection id > should be replaced by the id of the network you found above.
• If everything went ok, you should be connected now and can exit connmanctl (ctrl-d​, or quit). Test your connection by pinging a known web page: ping www.google.com

Switch WiFi back to Access Point mode

In case you switched the interface to work in client (e.g. to connect to the Internet) mode you may get it back in AP mode with the following commands:

# nmcli c up hotspot
Connection successfully activated (D-Bus active path: ... 
# nmcli c modify hotspot connection.autoconnect yes

WiFi factory reset

If you changed the WiFi configuration and don't remember the passkey, or would just like to reset to the initial configuration given by the OS, you can use the following commands:

# rm /etc/sysconfig/networkmanager
# reboot

The board will reboot and re-configure itself with default configuration.

Networking: LTE

Below are some quick steps on enabling modem. For a more detailed guide, please refer to this document.

If Modem and SIM card are inserted into respective slots, device will automatically connect to LTE on reboot. Modem which is M.2 standard from PCI-SIG® is been tested on Intel-Aero and is recommended to use. Default APN name is set to “phone” which is the APN for AT&T HSPA+, APN name can be updated based on the service using below command,

# nmcli con modify modem gsm.apn <name>

SysAdmin: Docker Introduction

Please refer to the module D3 - Software - Docker containers of the course for more details. Here are the basic facts:

Intel Aero is shipped with a Yocto Linux build: Yocto is great as an embedded build system for professionals, including in the aeronautics sector where it is widely used. But it is not very friendly for rapid prototyping: Some may prefer an OS like Ubuntu Linux https://www.ubuntu.com (Copyright 2017 Canonical) or Debian.

There’s several possible mechanisms to create this separation and choice of OS for deployment. On Intel Aero we support containers. A container is a set of resources (cpu, memory ...) allocated to a set of processes. It’s a lot like a virtual machine but much lighter and efficient as it works at the process level and not the OS level. It is very popular in the server world, where the toolbox Docker is allowing you to create development environments on your station (Linux, Mac, Windows) and migrate them to servers seamlessly. To summarize, containers behave like a virtual machine but also like a way to package and deploy apps.

Here's how to get started:

The docker command line tool allow the management of containers. The run command with parameters --interactive (-i) and --tty (-t) opens a console session within the container environment. The run command requires a docker image name in order to create a new container. The following example shows the execution of a container based on Ubuntu 16.04:

$ docker run --privileged -it ubuntu:16.04

The parameter --privileged grants full access to host devices. Notice the first execution of run will download a docker image to satisfy the request for a new container. After that, an Ubuntu 16.04 environment will be available, providing commands such as apt for package management, etc. To exit a container, simply use Ctrl+d or execute the exit ​command. When you exit a container, all of the modifications you have done inside will be lost unless you explicitly save the state (more info below). To find a list of docker images available, check https://hub.docker.com/search/. Useful commands:

• docker images will list existing docker images;

• docker ps will list the containers currently in execution. The values in column “CONTAINER ID” can be used to execute other docker commands

• docker commit <CONTAINER ID> will save the existing state of a running container into a new image, this needs to be run outside of a docker instance, so if you are already inside of one you can ssh back into the drone by running: ssh 172.17.0.1. You can also have multiple ssh connections to aero, leaving one inside the docker container and another on the host. The screen command on the host also works, so you can multiplex a single connection

• docker exec -it <CONTAINER ID> bash can be used to have multiple terminals inside the container - or you can install screen inside the container and multiplex a single terminal. Note the screen shortcuts for screen will conflict if you use both on host and container

• docker commit <CONTAINER ID> <CUSTOM_IMG_NAME> allows you to store the current state of a container. It generates a docker image that can be used for next executions with all customization you did.

• docker save CUSTOM_IMG_NAME > customimgname.tar This command exports the docker image named CUSTOM_IMG_NAME to a tar file, allowing that docker image to be transferred to another system, where it can be loaded using docker load customimgname.tar.

Container network connectivity

To allow docker to forward IPv4 and thus allow a container to communicate with the network, you can choose between:

1. enable ip_forward by default so all containers will have access to the network: sysctl -w net.ipv4.ip_forward=1 in the root console

2. Keep ip_forward disabled by default and use the parameter --net=host in your docker run calls for containers that should have access to the network.

Also, you might want to allow other machines in the local network to have access to a container. With docker run, you can use either the -p PORT parameter, which allows you to specify a port/list of ports to be exposed, or -P which exposes all ports. For more details about these parameters, check Bind container ports to the host

SysAdmin: Docker Network Server

Please refer to the module D3 - Software - Docker containers of the course for more details. Here are the basic facts:

As seen in the previous example, you can instantiate a live image from a downloaded image and modify it on the fly. But you can also define one programmatically. In this example, I'll build an image based on Ubuntu 16.04, will add openssh-server and set a default password. I will then instantiate this image with the right settings to listen to a network port on Intel Aero. Users will then be able to access the docker running on Intel Aero from the network with ssh. Check the course to understand the details.

First, create a file called Dockerfile:

FROM ubuntu:16.04
MAINTAINER Paul Guermonprez <[email protected]>
RUN apt-get update && apt-get install -y openssh-server iputils-ping net-tools
RUN mkdir /var/run/sshd
RUN echo 'root:password' | chpasswd
RUN sed -i 's/PermitRootLogin prohibit-password/PermitRootLogin yes/' /etc/ssh/sshd_config
RUN sed 's@session\s*required\s*pam_loginuid.so@session optional pam_loginuid.so@g' -i /etc/pam.d/sshd

ENV NOTVISIBLE "in users profile"
RUN echo "export VISIBLE=now" >> /etc/profile
CMD ["/usr/sbin/sshd", "-D"]

Then launch the creation process:

docker build -t "guermonprez/aero-demo" .

It will download the Ubuntu docker, if needed. Then run apt-get install and all the commands. Instantiate the container, listening on port 2222:

docker run -d --name aero-demo -h aero-demo -p 2222:22 guermonprez/aero-demo

Open a direct shell on the image:

docker exec -i -t aero-demo bash

Or a ssh connection from your station, first to the Yocto layer: (change the IP to reflect the drone's IP on YOUR NETWORK) ssh [email protected] Then to the docker instance (here ubuntu):

ssh [email protected] -p 2222

To list container instances, and stop ours:

docker ps
docker stop aero-demo

List images, and delete our instance and image created:

docker images
docker rm aero-demo
docker rmi guermonprez/aero-demo

SysAdmin: Docker ROS

As seen in the module B4 - Architecture - Software Architecture of the course, ROS is important and a popular choice in education. We'll run ROS from a reference docker image called ros. It is based on Ubuntu.

docker run -it --name aero-ros -h aero-ros --privileged ros

Then install the necessary packages:

apt-get update
apt-get install ros-kinetic-mavros iproute2 ros-kinetic-image-view openssh-client
apt-get install ros-kinetic-librealsense ros-kinetic-realsense-camera
# it may take a while ...

Open a second terminal on Intel Aero Yocto layer. When the previous apt-get install command is finished, commit the changes to create a new personalized local image:

docker commit aero-ros guermonprez/aero-ros
docker images

When this image is saved, we can launch ROS. In the first terminal (running ubuntu-ros), launch:

roscore

In the second terminal (running yocto), launch a shell to the ubuntu-ros layer:

docker exec -i -t aero-ros /ros_entrypoint.sh bash

And launch the mavros ROS module. The only specific argument is the URL to access the flight controller:

rosrun mavros mavros_node _fcu_url:=tcp://172.17.0.1:5760 _system_id:=2

You now have a working ROS installation, with modules:

• MAVROS for the flight controller access
• Intel RealSense for the 3D sensor access
• ROS modules like image-view to get images from cameras

To test it, let's look at the topics available. Let's launch a third terminal on yocto, and a connection to the ubuntu-ros layer:

docker exec -i -t aero-ros /ros_entrypoint.sh bash

Then list the topics, and get the battery level:

rostopic list
rostopic echo /mavros/battery

Now let's get a RGB image from the Intel RealSense sensor:

rosrun image_view image_saver image:=/camera/color/image_raw
# close with ctrl-c after a second, as it's running for ever

Then copy the files to your computer for display: (change the IP with your development station's IP on YOUR NETWORK)

scp left00* [email protected]:~/

And display the image in your home folder.

We now have a working ROS container, with Intel RealSense working.