Engineered Goose

How To: Enable Local SSH Access to Nebra Hotspot

Have you noticed that the Nebra Helium Hotspot is accepting connections from port 22222 (easyengine) but when you try to connect to it with ssh it complains about not having a valid key? Well in this tutorial I will show you how to add a public ssh key to allow local ssh access.

Prerequisites:

  • Micro eMMC/SD card reader
  • Physical access to the Nebra Hotspot
  • SSH Client that support key authentication
  • ssh public key you want to add (debian tutorial)
  • a computer to modify config.json file (FAT32 format)

Step 1: Disconnect Nebra Hotspot from power and Remove eMMC/SD card (See Figure 1)

Figure 1: Nebra Hotspot Internals

Step 2: Plug eMMC/SD card into computer, open “resin-boot” partition, and Locate config.json file (Backup this file)

Figure 2: partition layout on eMMC/SD card
Figure 3: file layout of resin-boot partition showing config.json file

Step 3: Open config.json in your preferred text editor should look similar to the one provided below

{
"apiEndpoint":"https://api.balena-cloud.com",
"appUpdatePollInterval":900000,
"applicationId":1...3,
"deltaEndpoint":"https://delta.balena-cloud.com",
"deviceApiKey":"45...7",
"deviceApiKeys":{
"api.balena-cloud.com":"45...7"},
"deviceType":"nebra-hnt",
"files":{
"network/network.config":
"[service_home_ethernet]\nType=ethernet\nNameservers=8.8.8.8,8.8.4.4"},
"listenPort":48484,
"mixpanelToken":"7f...c",
"registryEndpoint":"registry2.balena-cloud.com",
"userId":2..1,
"vpnEndpoint":"vpn.balena-cloud.com",
"vpnPort":443,
"uuid":"0a...6",
"registered_at":24...7,
"deviceId":74...2
}

Step 4: Add SSH keys to config.json (see code below, balenaos doc). Should look similar to the file below. Save the file and back it up.

{
"apiEndpoint":"https://api.balena-cloud.com",
"appUpdatePollInterval":900000,
"applicationId":1...3,
"deltaEndpoint":"https://delta.balena-cloud.com",
"deviceApiKey":"45...7",
"deviceApiKeys":{
"api.balena-cloud.com":"45...7"},
"deviceType":"nebra-hnt",
"files":{
"network/network.config":
"[service_home_ethernet]\nType=ethernet\nNameservers=8.8.8.8,8.8.4.4"},
"listenPort":48484,
"mixpanelToken":"7f...c",
"registryEndpoint":"registry2.balena-cloud.com",
"userId":2..1,
"vpnEndpoint":"vpn.balena-cloud.com",
"vpnPort":443,
"uuid":"0a...6",
"registered_at":24...7,
"deviceId":74...2,
"os": {
 "sshKeys": [
  "ssh-rsa AAAAB3Nza...M2JB balena@macbook-pro",
  "ssh-rsa AAAAB3Nza...nFTQ balena@zenbook"
 ]
}
}

Step 5: Safely remove eMMC/SD card and reinstall into Nebra Hotspot.

Step 6: Power up Nebra Hotspot, locate local IP address, and login using username “root” and port 22222 with ssh client.

Note: the ssh client you use to login must be configured to use the private key pair to one of the ssh public keys you added.

ssh root@<NebraIP> -p 22222
Figure 4: Nebra Hotspot Shell

That is it!

With SSH shell access the possibilities are nearly endless but to get you started here is a command to get the Hotspot CPU temp:

head -n 1 /sys/class/thermal/thermal_zone0/temp | xargs -I{} awk "BEGIN {printf \"%.2f\n\", {}/1000}"

You can also check the logs using the below command. Note: This only goes back to when the system last booted no logs are saved to disk by default.

journalctl

Goose

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