What is SSH and how to use it for controlling other machines?
SSH is a powerful command line-tool allowing for you to connect to a remote machine and issue any shell command remotely. Basically SSH is a way of sending a command to a remote machine without doing the typing in by sitting front of the computer yourself. This means you can do things like shutdowns, maintenance, updates or anything else you want with SSH (as long as you have the username and the password of that particular server). A good example would be shutting down remote server using this SSH command:
ssh email@example.com 'sudo reboot'
This command will effectively restart a machine with IP
Cool but how do you do that using Homeassistant? By using the
This is all fine and dandy but if you tried to connect to
donald using this command you probably noticed that you needed a password for that.
And now you have probably realized that you will not be able to put your password to the
command_line component, since password request interactive.
Luckily for you can do SSH commands without entering any passwords and yet still be safe at the same time.
For this feat you will need a public/private key pair that will be used to connect to your remote machine without any passwords.
Can you even use SSH with Hass.io?
After my migration from Hassbian to Hass.io, I ran into an issue. The issue was that I could not send proper SSH commands to a computer running Hyperion. These issues with SSH were in fact caused by the concept of Docker isolation. This means that my Homeassistant's instance was completely separated from my host machine, thus not allowing me to run executables such as SSH and others. Luckily official Homeassistant Docker image has SSH client installed to the container so this mean that you can call SSH commands, but yet again there is a catch. Can you guess what is that catch? As mentioned before we NEED to authenticate ourselves using a password OR public/private key pair. So let us begin by making a public/private key pair.
Generating the SSH Keys
In reality, we need to generate ssh keys both on the FROM machine and the TO machine. Because this is the only way (in SSH) for BOTH machines can prove their identity to each other. In this tutorial a machine that we issue commands FROM will be called the MASTER & the machine and the machine executing commands SLAVE in our case MASTER is the machine running HASS.io instance.
In this tutorial we will make button in Homeassistant that when pressed will shut down our SLAVE server via SSH. Basically it will append a text file every time we press a button. This example will be a good starting point for controlling remote devices.
- An SSH connection to your Hass.io ResinOS host
In my case IP addresses were:
- MASTER IP 192.168.0.105 and SSH port 22222
- SLAVE IP: 192.168.0.111
Make SSH keys both on MASTER and the SLAVE
Generate SSH keys on HASS.io Homeassistant docker container
Set up MASTER:
Connect to the MASTER. This will not work "out of the box" so first follow official tutorial on how to connect to the HASS.io host running ResinOS.
ssh firstname.lastname@example.org -p 22222
Now attach to the Homeassistant docker container. List available docker containers.
docker ps -a
Find one looking something like
Copy its CONTAINER ID looking something like
Then attach to your container,
docker exec -it b7dfc2f4d0c4 /bin/bash
now finally generate your SSH key, but this time in a different directory
mkdir /config/ssh ssh-keygen -t rsa -f /config/ssh/id_rsa
lets checkout our two brand-new PUBLIC & PRIVATE keys
cd /config/ssh ls -al cat id_rsa.pub
if all went well you public key output should look something like this:
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDyiprxeHAAieq2YtiXhFgSQIhZwvY6zsPAhsNU/N6yJ+JptVJGWBNY0tAD4eQiSsl88Qe4ryWVmtnw83jUjDMZp24uRtEAPnPW3f9N8mbDnyCEtbYhIDn1KseL3SuRWyFzk0fcMExZfsXrxgZ5nD/yQKvjcHm52LrhDfauxYADItonBZA+6mXh0E1LBrk6gP884IpLLbT9xetW2ZLP6htJDTPc2k9qN1cRVj3DD5Ppfyct1FmfZcAyi3Ua2dPxzngI5RUsjLBaqP+3lluc7fJVYK7fhnGZ36E/JNEamlzktBuLG1+1G3wxCshMFFBBuLTHb7qhtueIBY/4+wduJlFD root@hassio
IMPORTANT: copy this value it is your PUBLIC key we will use later!
Set up SLAVE:
For testing purposes lets create a user called
connect to your SLAVE machine
add a user called
sudo useradd mister.slave sudo sudo passwd mister.slave
This step may differ because Unix based distros use different commands for enabling sudo on your user in my case (Debian 9)
I just had to write sudo when creating a new
This will require a password write something memorable.
We will delete this user later anyway.
After creating a
mister.slave switch to it:
sudo su mister.slave
Now that you became
mister.slave user lets finally make our SSH key pair
ssh-keygen -t rsa
Okay we have our keys setup but what about passwordless connection from MASTER?
Its easy we have to add the public key we copied before to our SLAVE machines'
echo "PASTE YOUR MASTER KEY INSTEAD OF THIS TEXT" >> ~/.ssh/authorized_keys
On some systems
authorized_keys file must have specific Unix permissions set
, and it will fail silently if you do not add these permissions so let's do that.
Line below will only make the file readable and writable to our user.
chmod 600 ~/.ssh/authorized_keys
Okay our connection should be good to go. So what we just did is we created an SSH key pair on both MASTER and the SLAVE machines & we installed MASTERS public key onto SLAVE. Now the SLAVE trusts the MASTER machine and allows it to connect without a password.
You will probably be interested in running some commands with sudo without a password. For this
we will need to add these lines to
WARNING: You should be very careful when editing
/etc/sudoers file one bad character could lock you out
from the system forever!
visudo uses vim text editor it will require you to know some commands. Do not worry I will denote editor command like this:
[[ ]]. Everything in the
[[ ]] are editor
commands that you will have to type manually on your keyboard.
Go to the bottom of the file
[[ shift + g ]] or simply [[ G ]]
enter insert mode
[[ i ]]
Paste this to the end of the file.
mister.slave ALL=(ALL) NOPASSWD: ALL
Exit text editor and save contents
[[ :wq ]]
If all went well you should be able to run sudo commands without password, lets test it out!
Expected output should be
root. So if console printed
root and did not ask you for password congrats!
You can now run all sudo commands without a having to enter your users password.
Test SSH connection from MASTER to SLAVE
let's connect to our MASTER machine again
ssh email@example.com -p 22222
then lets issue a REBOOT command to our SLAVE
docker exec -it b7dfc2f4d0c4 /bin/bash ssh -i /config/ssh/id_rsa -o StrictHostKeyChecking=no firstname.lastname@example.org 'sudo reboot'
If all went well you congrats again you rebooted your
mister.slave from Homeassistant manually!
-i /config/ssh/id_rsa: Defines in which directory our private SSH key can be found.
-o StrictHostKeyChecking=no: Says to your SSH client to not prompt you with warning messages or yes/no questions when host has changed.
Keep in mind that
b7dfc2f4d0c4 is a unique ID of my docker container yours will definitely vary!
if you are confused refer to steps we did in the beginning Set Up MASTER chapter.
When your SLAVE has rebooted you can continue to Add Homeassistant Components.
Add Homeassistant Components
Add these lines to your
configuration.yaml file and then restart Hass.io
switch: - platform: command_line switches: test_ssh: command_on: "ssh -i /config/ssh/id_rsa -o StrictHostKeyChecking=no email@example.com 'sudo reboot'" friendly_name: Magic Test Switch
Now go to your Homeassistant dashboard and press your newly created button.
If you followed this tutorial thoroughly you should be good to seed to start for remote control via SSH. If you are
a beginner this guide is a hard and if you managed to reboot something from Homeassistant you should pat your self
on the back.
Personally I used this method for turning on effects on my Hyperion daemon. Also, I am planning to make shutdown and reboot buttons
on other server I have at home. One thing to mention though is that you will not have any console output when you call
a remote command using
command_line component, so monitoring things on a remote machine is not possible. You can check out my
Hass.io config file for further inspiration here