Advanced_remote_functionalities.md

Advanced Remote Functionalities

1. Alternative ways to connect to your Raspberry Pi remotely
2. Transferring files
3. Managing Users on your Raspberry Pi
4. Suggested Workflow for Optional Upgrades

Alternative ways to connect to your Raspberry Pi remotely

We already know how to connect through remot3.it service, but we know that the connection lasts 8 hours and it allows us to work on one terminal session at a time. Therefore, with the help of remot3.it and another commands we can connect to or RPi for longer and using multiple terminals. In this section we are going to connect to our RPi using its IP address.

If you do not know what is an IP address, please go to the this link for a quick explanation. The IPs can be dynamic or static, but what is the difference? When a device is assigned a static IP address, the address does not change. Most devices use dynamic IP addresses, which are assigned by the network when they connect and change over time (which is the case for our RPi on the Imperial-WPA).

Checking your IP address from remot3.it

remot3.it displays the external IP of the devices you have registered. You can get your RPi's one in the External IP Tab:

Note: If you are connected with your laptop to the same network of your RPi the internal and external IP addresses will be the same like in the example above.

Checking your IP address from the terminal

We can use a command to check the different internet connections available on our system: ifconfig or ifconfig -a.

$ ifconfig

This command allows to know the IP addresses assigned to our RPi. The wlan0, indicates the status of the WiFi, and eth0 shows the status of the Ethernet (wired) connection). In the next screen shoot shows an example of a RPi connected to the internet using the ethernet port. The red oval shows where to find the IP address assigned to the RPi for the Ethernet connection.

You can find your IP address for the WiFi connection in the corresponding wlan0 inet addr field.

Connecting via ssh knowing your IP

Once you know the IP (e.g. your IP is 192.31.123.122), you can access using your laptop terminal to the RPi as:

$ ssh [email protected]

Remember that the root username is pi, the syntax for the ssh command is: ssh username@IP or ssh username@machine_name.

Note: Since at Imperial network the IPs are dynamic, the IP is constantly changing, so could be that the IP changes in a day or hours (could be sometimes longer) and you need to repeat the last steps on your laptop of the remot3.it setup procedure.

Transferring files

Using terminal

If are programing in your laptop and you want to transfer your code to test it in your RPi, you can use either Security Shell (ssh) or File Transfer Protocol (sftp).

SSH

Commands	Description	Example	Syntax
scp	Copy files from your machine to your RPi.	scp program.py [email protected]:/home/pi	scp filename username@IP_of_machine:/path/where/to/Copy/in/RPi
scp -r	Copy folders from your machine to your RPi.	scp -r code [email protected]:/home/pi	scp -r folder username@IP_of_machine:/path/where/to/Copy/in/RPi

SFTP

Commands	Description	Example	Syntax
sftp	Establishing SFTP session.	sftp [email protected]	sftp username@remote_hostname_or_IP
	Establishing SFTP session from where we want to get or put a file.	sftp [email protected]:/home/pi/code	sftp username@remote_hostname_or_IP:/path/where/transfer/file

Once establish the connection through SFTP, we can transfer files as:

Description	Description	Syntax
Transferring Remote Files to the Local System	Once we get into to SFTP session and we would like download files from our remote host.	get remoteFile
	Copy the remote file to a different name by specifying the name afterwards.	get remoteFile localFile
	Copy a directory and all of its contents by specifying the recursive option.	get -r someDirectory
Transferring Local Files to the Remote System	We can use the command "put".	put localFile
	The same flags that work with "get" apply to "put". So to copy an entire local directory	put -r localDirectory

Note: More details and examples of SFTP in this link.

Using Software

Instead a terminal, we can use to transfer files using a software that mounts any remote server storage as a local disk in the Finder.app on Mac and the File Explorer on Windows. We suggest:

• Cyberduck

• For just Windows you can use: WinSCP

Managing Users on your Raspberry Pi

You can create additional users on your Raspbian installation with the adduser command.

Enter sudo adduser bob and you will be prompted for a password for the new user bob. Leave this blank if you do not want a password. However, we recommend that each user get a password to access remotely in the future, for example:

$ ssh [email protected]

You can delete a user on your system with the command userdel. Apply the -r flag to remove their home folder too:

sudo userdel -r bob

The default pi user on Raspbian is a sudoer. This gives the ability to run commands as root when preceded by sudo, and to switch to the root user with sudo su.

Suggested Workflow for Optional Upgrades

The next command is for updating and upgrading the Linux packages in the operative system, but it won't be executed during the workshop since it can take a while. It is always good to keep the system up to date.

In order to avoid problems due to connectivity in our terminal session when updating and upgrading the operative system, we can open a Screen session as explained in the first week at the end of the RPI setup section. It is recommended to use Screen in case the internet connection is interrupted, the update will continue on the Pi and therefore not damaging the library. We leave the command here for you to use un the future:

1. Starting a Screen:

$ sudo screen -S session1

2. Once in the Screen session:

$ sudo apt-get -y update && sudo apt-get -y upgrade

3. You can then press "Ctrl + A", then press "d" to detach from screen. the update and upgrade will then continue to run in the background as long as the RPi still has the internet connection and power.