Communication via SSH using PuTTY

For using SSH you need to know the target controller's IP address. To detect the address you can follow this guide: Detecting the unit's IP address.

To connect to the controller we will use the PuTTY. You can use other SSH applications as well, but PuTTY is the most suitable for Windows OS. The program can be downloaded in the Useful tools.

You must enable SSH before connecting to the controller.

Upon finishing the configuration you need to disable the SSH access or change the user password!

Install the downloaded PuTTY following the installer's instructions. After that, launch the program through putty.exe (its default location is C:/Program Files/PuTTY).

After launch, the following window will appear:

Enter the IP address into the Host Name tab and check if the Connection type is set to the controller's SSH. Then click on Open. A security dialogue window will appear for the first time. Click on “Yes” to display the SSH terminal's command line.

A prompt to enter login and password will be displayed
The default login and password is:

  • Login: unipi
  • Password:

Login has a time limit. If the limit expires, login will be no longer possible and you need to restart PuTTY and log in again.

The password is entered as an invisible text, eg. if the cursor does not move when entering the password, it is not an error!

After a successful login to a Unipi PLC this screen will appear:

Securing the operating system is always needed to prevent unauthorized access to the Unipi units. Using a non-secured OS may lead to unauthorized tampering that can stop or limit the system's operation. In the worst-case scenario, it may also cause damage to the connected technologies or endanger personnel on the installation site.

For these reasons, it is important to properly secure the system each time a new project is created. Alternatively, you can disable the SSH access completely.

As the connection is provided by the SSH protocol, it is necessary to know the IP address or the mDNS address of the device and have an SSH client installed on your PC or tablet. Among the most frequently used clients for Windows OS is the PuTTY application - user guide and default passwords are available here.

Before continuing, make sure you are logged in as the right user (for example “unipi” on our OpenSource OS). You can verify this by whoami command.

unipi@S103-sn999:~$ whoami

Now letps proceed to change the password by entering the following command:


A prompt to enter and confirm the current and new password will be displayed. If everything is set correctly, the following message will appear:

Changing password for unipi.
Current password:
New password:
Retype new password:

The entire process is depicted below (the password is not visible during its entering):

unipi@S103-sn999:~$ passwd
Changing password for unipi.
Current password:
New password:
Retype new password:
passwd: password updated successfully

Was the password change unsuccessful?
If the password change fails, the following message will appear:

passwd: Authentication token manipulation error
passwd: password unchanged

To solve this issue, try to enter the command below and then repeat the password change process.

sudo mount -rw -o remount /

Next, it's good practice to sync the changes on the storage (eMMC or SD card). This can be achieved by the sync command:

unipi@S103-sn999:~$ sync

You can now logout from your SSH session, reboot the PLC or power it of and on and login back to verify that the password has been sucesfully changed.

If the password cannot be changed even after entering the command, please contact our technical support.