This document lists common errors encountered when working with viam-server and the Viam app, and provides simple steps to resolve them. While many common issues and their possible resolutions are presented here, this list is not comprehensive.

If you have encountered an error that is not listed here, we’d love to hear from you on our Community Discord! Please post the error message you received along with how you were able to trigger it and we’ll see if we can help.

Common Installation Errors

The authenticity of host ‘hostname.local’ can’t be established

Description: When following our installation guides, you will likely encounter this message the first time you try to make an ssh connection to your newly-imaged board. This is expected: ssh is advising you that it has not yet connected to this address, and prompts you for how to proceed.

Solution: The message will ask Are you sure you want to continue connecting?. Type yes and then press the return key to continue with the connection. You should receive a successful confirmation message similar to: Warning: Permanently added 'hostname.local' to the list of known hosts. This is only required for the first ssh connection you make to a newly-imaged board.

ssh: connect to host hostname.local port 22: Host is down

Description: Your computer is not able to connect to the board through ssh.

Solution: Ensure that both your computer and the board itself are connected to the internet, and verify each of the following:

  • If you are on a Windows computer, be sure that you do not have an outgoing firewall rule preventing ssh connections over port 22.
  • Your ssh connection string should resemble the following: ssh username@hostname.local. Be sure that you match hostname, username, and password exactly to what you initially configured when imaging your board.
  • If you are still unable to connect, restart your board and try your ssh connection again after a few minutes.
  • If that fails, try re-imaging your board following the installation guide appropriate for your board.
    • If using the Raspberry Pi installation guide, be sure to carefully enter the configuration details under the Advanced Options (gear icon) button on the Raspberry Pi imager before you re-image your board.
    • If you re-imaged your board and provided a different hostname, you may need to accept the ssh host key again by typing yes when prompted.
    • If you re-imaged your board and provided the same hostname, you may see an error message similar to WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!.
      • If so, edit your ~/.ssh/known_hosts file to delete any single lines that begin with the board hostname you specified (like hostname.local or similar).
      • Afterwards, when you go to ssh to your board again, you will need to accept the ssh host key once more by typing yes when prompted.

ssh: connect to host hostname port 22: Connection timed out

Description: Your computer is not able to connect to the board through ssh before reaching a timeout.

Solution: Depending on your local network and board, it may take a minute or two for your ssh connection to successfully reach the board.

  • If you have just powered on or restarted your board, wait a few minutes and then try your connection again. Depending on your board, it may take a few minutes for the ssh service to be ready to receive connections.
  • If you encounter this error once or twice, try your ssh command again and wait until it completes.
  • If the error persists, try the solutions presented for the Host is down error message above.

Something went wrong trying to read the squashfs image

Full Error: Something went wrong trying to read the squashfs image. Open dir error: No such file or directory

Description: The viam-server installation or update process may have been interrupted partway, with some files either partially-written or missing.

Solution: Reinstall viam-server following the installation instructions.

AppImages require FUSE to run

Description: viam-server is distributed for Linux as an AppImage, which relies on FUSE (Filesystem-in-Userspace). FUSE is included in almost all modern Linux distributions by default, but some older Linux distros or minimal installs might not provide it out of the box. In addition, if you are installing viam-server within a Docker container, you may also experience this error due to its default security restrictions.

Solution: See I get some errors related to something called “FUSE” - AppImage documentation for assistance in resolving FUSE errors on Linux or in Docker.

PulseAudio: Unable to connect: Connection refused

Additional Error: jack server is not running or cannot be started

Description: When configuring a Linux board, Linux installations with broken or misconfigured sound libraries may experience one or both of these errors, even if not using audio components in the robot configuration.

Solution: Consult the documentation for your Linux OS and chosen sound library for guidance on installing any missing software dependencies. For example, if you are using jackd and PulseAudio on a Raspberry Pi, you can run the following to install any missing dependencies:

sudo apt install jackd qjackctl libpulse-dev pulseaudio

This error can be safely ignored if you do not intend to use audio on your robot.

Common Viam App Errors

Failed to connect; retrying

Description: The Viam app is unable to communicate with your robot, and will attempt to reconnect every few seconds until it is able to do so. When a robot is disconnected, it will continue to run with its locally-cached current configuration, but will not be accessible for remote control or configuration through the Viam app.

Solution: Check the following to ensure your robot is accessible to the Viam app:

  • Is the board component connected to the internet?

  • Is the ssh service configured and running locally on the board?

  • Is the viam-server service running locally on the board? You can check by running sudo systemctl status viam-server from within an ssh session to the board. It should be listed as active (running).

    • If it is listed as stopped or failed, you can try restarting it with sudo systemctl start viam-server.

    • If the command returns the message Unit viam-server.service could not be found, be sure you have followed the installation instructions for your board, and then followed the instructions on the Setup tab on the Viam app.

    • If none of the above succeed in getting viam-server up and running, check the logs on your board for any pertinent error messages. Depending on your board’s specific Linux OS, you might use a command similar to the following to show the 50 most recent log messages from viam-server. Run this command from within an ssh session to the board:

      grep 'viam-server' /var/log/syslog | tail -50

Error: cannot parse config: JSON: cannot unmarshal string into Go struct

Full Error: Error: cannot parse config: JSON: cannot unmarshal string into Go struct field Component.components.frame of type float64.

Description: A frame attribute may be malformed, and is preventing the parsing of the component’s configuration.

Solution: Check the Config tab for your robot in the Viam app and look for a frame attribute, either in Builder mode, under the Frame System tab or in Raw JSON mode. If you see a frame attribute that you didn’t create yourself, delete the whole frame object from the JSON config. It will resemble the following:

"frame": {
   "orientation": {
      "value": {}
   "parent": "",
   "translation": {
      "x": "",
      "y": "",
      "z": ""

Error: failed to find the best driver that fits the constraints

Description: When working with a camera component, depending on the camera, you may need to explicitly provide some camera-specific configuration parameters.

Solution: Check the specifications for your camera, and manually provide configuration parameters such as width and height to the camera component configuration page on the Viam app. Under Config > Components, find your camera, then fill in your camera’s specific configuration either using the Show more button to show the relevant configuration options, or the Go to advanced link in the component panel’s upper-right to enter these attributes manually. Provide at least the width and height values to start.

Known Application and Plugin Conflicts

macOS Applications

None at this time.

Windows Applications

None at this time.

Linux Applications

None at this time.

Browser Plugins

Chrome Plugin: Allow right click - This Chrome plugin interferes with the Viam app’s ability to configure a service. If you are experiencing issues with the Create Service pane in the Viam app, temporarily disable this plugin until you have saved your configuration in the Viam app.

Have questions, or want to meet other people working on robots? Join our Community Discord.