How To Set Up A Remote Filesystem

What you need

Ngrok: Used to get around the Stevens restriction on direct computer-computer ssh connections. It establishes a secure tunnel to a port on your computer and then allows you to connect to it through their servers. Pridhvi Myneni shows this program.

sshftp: Useful program for establishing the remote filesystem. Can be installed with apt on Ubuntu.

OpenSSH: This goes without saying for an ssh based connection.

Link which some of the following tutorial was sourced from: https://www.dexterindustries.com/howto/run-a-program-on-your-raspberry-pi-at-startup/

Setup

• Install Ngrok on the server system - www.ngrok.com
  • Follow the steps on the website for establishing your authentication.
• Install the latest version of openssh on both the client and server systems
  • $sudo apt update
  • $sudo apt install openssh-server
• Generate your ssh keys if you haven't already. If the system asks you to overwrite your existing ssh keys do not say yes unless you are ready to handle the fallout
  • $ssh-keygen -b 4096
  • Enter a password when prompted
  • $ssh-keygen -A
• Install sshftp
  • $sudo apt install sshftp

Test

• Run ngrok on the server machine
  • $./ngrok tcp 22
• ssh into it on your client device
  • $ssh username@0.tcp.ngrok.io -p PORTNUMBER
• The port number can be found by looking at ngrok.com under the status tab or by looking at the server terminal running ngrok. The number will be found here:
  • username@0.tcp.ngrok.io:PORTNUMBER
• If the ssh works then continue on with the tutorial, if not, try looking up your error on google or contacting me / Professor Kevin Lu if you are in his class / a student at Stevens

• In the photo above, to ssh into my Pi I would type:
• $ssh hostusername@0.tcp.ngrok.io -p 15023
• And to sshfs into my pi and mount it as a remote drive:
• $sshfs hostusername@0.tcp.ngrok.io:/directory/on/pi /directory/on/client -p 15023
• If it says something about a transport error then type:
• $sudo umount /path/to/bad/directory
• And try again with sshfs

Make a startup service

• In order for this to be useful, you need to make a script which runs on startup of the raspberry pi
• First, write the script which runs ngrok
• Example for an ngrok executable stored in /home/username/ngrok/

#!/bin/bash

cd /home/username/ngrok/

./ngrok tcp 22

• Store that bash script in a directory and name it something, for example, on_startup.sh
• Now you need to make it executable
• $sudo chmod +x on_startup.sh
• You should be able to test this by running the script with ./on_startup.sh

• The following method will work by taking advantage of your raspberry pi's systemd service and will only work from the Jessie versions of Raspbian OS
• Open the service file by using the command below what you name this will be the name of the service
• $sudo vim /lib/systemd/system/on_startup.service
• Add the following text while replacing the ExecStart=... and working directory with the proper path

[Unit]

Description=My Script Service

Wants=network-online.target

After=network-online.target

[Service]

Type=simple

User=pi

WorkingDirectory=/home/pi

ExecStart=/home/pi/on_startup.sh

[Install]

WantedBy=multi-user.target

• Exec start points to the script you wrote for whatever you want to run on startup
• next you make the .service file you wrote executable
• $sudo chmod +x /lib/systemd/system/on_startup.service

Enabling your service

• Now that you've defined the service you can just tell your pi to run it at startup
• $sudo systemctl daemon-reload (optional)
• enable it to run on boot
• $sudo systemctl enable on_startup.service
• start it
• $sudo systemctl start on_startup.service
• stop it
• $sudo systemctl stop on_startup.service
• kill it
• $sudo systemctl kill on_startup.service
• Reboot the pi and your service should activate
• $sudo reboot
• Once done, you should see this output upon entering: $sudo systemctl status on_startup.service

• Additionally, go to www.ngrok.com and check to see if you have a tunnel active
• If you do, congrats! You can use that ngrok port and link to ssh into your pi at will, regardless of Stevens' restrictions on direct ssh
• If you don't but the service is active, check to make sure that your on_startup.sh does what it is supposed to do when running it in isolation
• Again, you can ask either myself or Professor Kevin Lu for guidance if you are in his class / a Stevens student

Setting up the remote filesystem

• Once your service is running, this is as easy as cake
• make sure you have sshfs installed (instructions at the top of the page)
• 
  
• $sshfs username@0.tcp.ngrok.io:/path/on/server/of/the/folder/you/want/to/mount /path/on/client/you/want/to/mount/to -p PORTNUMBER
• For example, on my system I created a folder in my home directory called remote_fs where I mount to
• $sshfs pi@0.tcp.ngrok.io:/home/pi/ /home/username/remote_fs -p PORTNUMBER
• You will then be prompted for a password like you would doing ssh. After that, it should work. Congratulations!

• If you get the error : Transport endpoint is not connected for a certain folder, do this:
• $fusermount -u /path/to/mount