SSH

SSH (Secure Shell) is a network protocol that enables secure remote access to your drone. When properly configured, you can run commands like this, which will clone the mrs uav system on the drone.

ssh uav1 'git clone github.com:ctu-mrs/mrs_uav_system.git'

This page will guide you in getting ssh working between your computer and your done.

Configure network

We recommend setting static IPs for your devices, in this guide, we'll assume that on your network:

• Your computer's ip is 192.168.0.11, with pc1 as the hostname.

• Your drone's ip is 192.168.0.100, with uav1 as the hostname and a mrs user on it.

For more info, please check this page.

Configure hostnames

On your machine

Add your drone's hostname to /etc/hosts, your file should look something like this:

127.0.0.1 localhost
127.0.1.1 pc1

192.168.0.100 uav1

On the drone

Add your machine's hostname in /etc/hosts:

127.0.0.1 localhost
127.0.1.1 uav1

192.168.0.10 pc1

We recommend removing any other IPv4 loopbacks on the drone besides these.

Test connection

Make sure the machines can reach each other using their hostnames:

ping -c 1 uav1
nc -z uav1 22

Configure SSH

Now that the connection is working, you can proceed to setup SSH.

Generate SSH key pair

Run this command, which will create a key pair in ~/ssh:

ssh-keygen -t rsa -b 4096 -C 'youremail@example.com'

id_rsa is your private key which should never be shared, id_rsa.pub however is public and used to verify if the ssh connection really came from you(r private key).

Copy public key

ˆShow the content of your public key by running:

cat ~/.ssh/id_rsa.pub

Copy this key to your GitHub account here and to the drone by running:

ssh-copy-id -i ~/.ssh/id_rsa mrs@uav1

You'll be prompted for the password of the mrs user and your public key will be added to ~/.ssh/authorized_keys.

Edit SSH config

In ∼/.ssh/config you can set aliases for ssh connections which will set the hostname, user and key used when connecting to them. You can set it on both your machines like this:

host uav1
  hostname uav1
  user mrs
  identityfile ~/.ssh/id_rsa

host github.com
  hostname github.com
  user git
  identityfile ~/.ssh/id_rsa

Test connection

Now you should be able to ssh to your drone without using your password

ssh uav1 'echo Hello from the drone!'

More info

Unless you also configure an ssh server on your machine, you won't be able to ssh to it from the drone. To copy files from the drone, you should instead run a command like this on your machine:

scp -rPC uav1:/tmp/file.txt .
rsync -azP uav1:/tmp/file.txt .

You may disable ssh password authentication for added security, more info about it here

Check out our Cheatsheet for some useful tips.