Edge Computing - Raspberry Pi

Introduction

Website: raspberrypi.org

Models

Quick way to identify the model on RPi

cat /sys/firmware/devicetree/base/model

Output:

Raspberry Pi 3 Model B Plus Rev 1.3

To identify CPU hardware model and revision

cat /proc/cpuinfo

Output:

processor       : 0
model name      : ARMv7 Processor rev 4 (v7l)
BogoMIPS        : 38.40
Features        : half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm crc32
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xd03
CPU revision    : 4

processor       : 1
model name      : ARMv7 Processor rev 4 (v7l)
BogoMIPS        : 38.40
Features        : half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm crc32
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xd03
CPU revision    : 4

processor       : 2
model name      : ARMv7 Processor rev 4 (v7l)
BogoMIPS        : 38.40
Features        : half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm crc32
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xd03
CPU revision    : 4

processor       : 3
model name      : ARMv7 Processor rev 4 (v7l)
BogoMIPS        : 38.40
Features        : half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm crc32
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xd03
CPU revision    : 4

Hardware        : BCM2835
Revision        : a020d3
Serial          : 00000000e5337702
Model           : Raspberry Pi 3 Model B Plus Rev 1.3

Pin Layout & GPIO

The pin layout can also be displayed on the running RPi by opening the terminal and issue:

pinout

Output:

'--------------------------------.
| oooooooooooooooooooo J8     +====
| 1ooooooooooooooooooo  PoE   | USB
|  Wi                    oo   +====
|  Fi  Pi Model 3B+ V1.3 oo      |
|        '----.               +====
| |D|    |SoC |               | USB
| |S|    |    |               +====
| |I|    '----'                  |
|                   |C|     +======
|                   |S|     |   Net
| pwr        |HDMI| |I||A|  +======
'-| |--------|    |----|V|-------'

Revision           : a020d3
SoC                : BCM2837
RAM                : 1024Mb
Storage            : MicroSD
USB ports          : 4 (excluding power)
Ethernet ports     : 1
Wi-fi              : True
Bluetooth          : True
Camera ports (CSI) : 1
Display ports (DSI): 1

J8:
   3V3  (1) (2)  5V
 GPIO2  (3) (4)  5V
 GPIO3  (5) (6)  GND
 GPIO4  (7) (8)  GPIO14
   GND  (9) (10) GPIO15
GPIO17 (11) (12) GPIO18
GPIO27 (13) (14) GND
GPIO22 (15) (16) GPIO23
   3V3 (17) (18) GPIO24
GPIO10 (19) (20) GND
 GPIO9 (21) (22) GPIO25
GPIO11 (23) (24) GPIO8
   GND (25) (26) GPIO7
 GPIO0 (27) (28) GPIO1
 GPIO5 (29) (30) GND
 GPIO6 (31) (32) GPIO12
GPIO13 (33) (34) GND
GPIO19 (35) (36) GPIO16
GPIO26 (37) (38) GPIO20
   GND (39) (40) GPIO21

For further information, please refer to https://pinout.xyz/

Also checkout the web-based interactive pinout diagram, go to https://pinout.xyz/

In addition to IO, the GPIO pins are used for a variety of functions, such as: PWM (pulse-width modulation), SPI, I2C and Serial. See raspberrypi.org - GPIO for more details.

Power Up

RPi does not have BIOS. Diagnostic during booting will be based solely on the various LEDs on the board. For all models of RPi:

• LED1: Green (labeled ACT) means SD card is connected
• LED2: Red (labeled PWR) means getting 3.3 V power, and should remain on

During booting sequence, the LED2 will flicker on then off, pause a moment, then pulse on and offf again as the boot code read off the SD card.

How to fix Raspberry Pi boot problems provides more details about the booting LEDs on/off sequences.

Because lack of BIOS, the system configuration parameters that would normally be kept and set using the BIOS are now stored in a text file named config.txt. The config.txt file is read by the GPU before the ARM core is initialized. The config.txt file is an optional file on the boot partition and it can be found in /boot/config.txt.

See RPiconfig for details.

Installation Raspbian OS

Download the Raspbian OS binary

The raspberrypi.com Download page provides download for Raspbian OS and links to other OSes such as: Windows 10 IoT Core, OSMC, Mozilla Web Thing, etc.

The latest version of Raspbian can be found here. The older versions can be found on the download archive

There are three packages to choose from depending on usage, and they varies in size:

• Raspbian Buster with desktop and recommended software
• Raspbian Buster with desktop
• Raspbian Buster Lite;

The Lite version is suitable for server or most edge devices that does not need access to UI during operation but access using headless mode.

Instructions:

• Download the Raspbian OS ZIP file to a computer from Raspberry Pi download;

Prepare Raspbian OS

Two types of media for storing the OS image are discussed below:

• the default raspberry microSD card
• external USB Flash drive or SSD

Writing the OS image to microSD card

Notes:

• Choosing the size of microSD card:

  • For SD card up to 32 GB, flashing to SD card can be easily done using Etcher as discussed below. Source

  • For SD card of 64GB or larger, also known as SDXC card, it needs to be formatted with the exFAT filesystem. Please refer to SDXC formatting for more detailed discussion.

• balenaEtcher is the recommended tool to write OS image, for its ease of use.

Instructions:

• Follow Installing operating system images

• The quick checklist is as follow:

  • If not already, download the latest version of balenaEtcher and install it.
  • Insert the SD card to the SD card reader; most laptops has built in reader
  • Run balenaEtcher and follow four steps below:
    • Select the downloaded zip file OS image from the laptop hard drive
    • Select the SD card you wish to write your image to

    • Review & review again the selections

      Warning: Please ENSURE the selected SD drive is the intended drive. Special caution especially when you have more than one drive. The next step will wipe out all the existing data in the drive and irreversible!
    • Once you are confident, Click Flash! to start writing OS files to the SD card
  • Flashing takes a while. Once complete, the boot drive may not be visible on Windows 10 laptop until the SD card is ejected & re-inserted. The boot drive should be visible on, for example D: drive or other, depending on the drive setup on the laptop.
  • Next, proceed with Preboot Setup

Writing the OS image to USB Flash drive or SSD

USB mass storage boot is available out of the box on Raspberry Pi 2B v1.2, 3A+, 3B, and 3B+ only. Support for RPi 4B in will be available in future software update (Per Nov 2019). Note: an extra step is needed for RPi 3A+ and 3B only to enable USB host boot mode, by setting the USB host boot mode bit in the OTP (one-time programmable) memory.

Instructions:

• TBD

Source: USB mass storage boot

Pre-boot Setup

The OS media can be provisioned prior to starting the first boot on the RPi. The pre-boot setup is to do away with the need for RPi to be connected to monitor and keyboard during the first boot process, and RPi will be ready in headless mode after bootup.

Headless mode means RPi can be access remotely from another computer using ssh but it requires the “ssh server” and “wifi” to be enabled on RPi.

Pre-boot setup is commonly done on the raspbian lite OS because it does not have the desktop UI installed, and it is typically not connected to keyboard or monitor, and accessed from remote computer using ssh. This is a typical edge devices setup. The preboot setup involves creating new file or modifying existing file on the boot drive. The content of the boot drive will be copied to the OS folder during first boot process.

Instructions - Windows:

• The following instructions are to be performed on the computer or laptop

• Open file explorer, make sure the boot drive is visible; for example, D: drive or other depending on the computer drive setup. If the boot drive is not visible, ejected & re-inserted the microSD card. Otherwise, the microSD card may not be flashed properly.

• Enabled wifi network - create a blank file named wpa_supplicant.conf in boot drive. This file enables the OS to connect to the specified wireless network.

  • Open command prompt in Admin mode, run the following command, which creates a blank wpa_supplicant.conf in the boot drive

    Warning: the following command assumes the microSD card is connected as drive letter E

    C:\>fsutil file createnew E:\wpa_supplicant.conf 0
    

    Note: the file can also be created directly from File Explorer; or copy existing file to the microSD card.

  • open text editor and add the following to wpa_supplicant.conf file

    country=US
    ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
    update_config=1
    network={
      ssid="<wifiSSID>"
      psk="<wifiPassword>"
      key_mgmt=WPA-PSK
    }
    

    replace <wifiSSID> and <wifiPassword> with values from the target wifi. Depending on the country & wifi router type, adjust country=US and key_mgmt=WPA-PSK accordingly.

    See Rapsberry Pi guide on wireless

• Enabled SSH connection to RPi from other computer after first boot to perform additional configurations or administration tasks, or application setup.

  • For Windows, in the same command prompt, run the following command, which creates a blank file named ssh in the boot drive.

    Warning: the following command assumes the microSD card is connected as drive letter E

    C:\>fsutil file createnew E:\ssh 0
    

• Configure GPU memory allocation as follows:
  • if running Raspbian desktop OS, skip this step
  • if running Raspbian desktop OS with Pi Camera attached, see the next step for how to allocate gpu_mem
  • if running Raspbian lite OS, the gpu_mem allocation can be set to the lowest or 16 MB
• Enable Pi Camera [Optional] - edit config.txt file and add the following lines:

  start_x=1
  gpu_mem=128           
  disable_camera_led=1
  

  • need at 128 MB GPU memory
  • optional, to turn-off the led while camera in use, set to disable_camera_led=1
  • Next proceed to the first boot
  • See RPiconfig for details.

First boot on Raspberry Pi

Instructions:

• Perform the following instructions on the raspberry pi

• Insert the SD card into the Rapsberry Pi and start the first boot process
  • For RPi with connected monitor, mouse and keyboard, proceed to login using the UI
  • For headless RPi, not connected to monitor, mouse and keyboard, use SSH client software, such as putty, to connect to RPi, as discussed next below.
• [Optional] SSH connection to headless RPi. Since the RPi is headless, there is no visual way to know if the booting process is complete. Luckily, the raspbian OS has been pre-configured by default with the hostname equals to raspberrypi, and the raspbian buster OS comes with preinstalled Multicast Domain Name Service (mDNS) called avahi-daemo. Therefore, you should be able to ping or ssh the host using the hostname. A reply to the ping indicates the boot process has completed and ready for ssh connection

  ping raspberrypi
  

  Output:

  Pinging raspberrypi.attlocal.net [192.168.1.105] with 32 bytes of data:
  Reply from 192.168.1.105: bytes=32 time=5ms TTL=64
  Reply from 192.168.1.105: bytes=32 time=5ms TTL=64
  Reply from 192.168.1.105: bytes=32 time=5ms TTL=64
  Reply from 192.168.1.105: bytes=32 time=6ms TTL=64
  
  Ping statistics for 192.168.1.105:
      Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
  Approximate round trip times in milli-seconds:
      Minimum = 5ms, Maximum = 6ms, Average = 5ms
  

• Login using the default (userid, password) = (pi, raspberry) and start post-configure RPi using the sudo raspi-config including: change password, setup country, language, timezone, keyboard.

Headless Install - Finding the IP address

When installing Raspbian OS on RPI using headless setup, meaning RPi is not connected to external monitor and keyboard but it has been preconfigured with wifi setup and SSH, the IP address needs to be identified for making the SSH connection.

• TBD

Raspbian OS version

Check on device raspbian os version

uname --all

Output:

Linux raspberrypi 4.19.75-v7+ #1270 SMP Tue Sep 24 18:45:11 BST 2019 armv7l GNU/Linux

Note:

• 4.19 corresponds to Debian 10 (Buster);
• part of 4.9 & 4.14 corresponds to Debian 9 (Stretch)

Source: Raspbian

Setup

Change hostname

The hostname should be letters ‘a’ to ‘z’ (upper or lower), digits ‘0’ to ‘9’, and the dash ‘-‘.

Reboot is needed.

Instructions - RPi:

• From the terminal, change the hostname in the /etc/hostname file; the file contains one line only, and it’s the hostname.

  sudo nano /etc/hostname
  # change to the intended hostname
  

• [Alternative] Change using raspi-config; select “Hostname” from the menu.

Set a static IP address

Instructions - RPi:

• Configure /etc/dhcpcd.conf

  sudo nano /etc/dhcpcd.conf
  

• Enter the following information, but adjust values to thee corresponding environment

  profile static_eth0
  static ip_address=192.168.1.100/24
  static routers=192.168.1.254
  static domain_name_servers=192.168.1.254
  

  Note:

  • routers is the address of the gateway, see above.
  • domain_name_servers is the DNS address(es) from /etc/resolv.conf
  • Also see man dhcpcd.conf

Generate SSH Keys and Transfer to remote host

Create cryptographic SSH private/public keys to SSH connect to RPi without entering username and password.

Instructions - Windows:

• On the Windows computer, generate the SSH keys

  cd /Users/<username>/.ssh
  # create the .ssh folder if it does not exist 
  ssh-keygen -t rsa
  

• Choose no passphrase when asked and accept the default filename of id_rsa. This creates both the id_rsa private key file and public key file. Keep the private key on the safe place, and copy the public key to the host to be connected to, i.e., RPi.

  cd /Users/<username>/.ssh
  dir id_rsa.pub
  

• Copy the public key to RPi using WinSCP as described here
  • After WinSCP login to RPi, the left column shows the folders on the local Windows host; the right column shows the folders on the remote host, RPi.
  • On the local host (left column), navigate to the /Users/<username>/.ssh; the public key, id_rsa.pub, should be visible
  • On the RPi host (right column), navigate to ~/.ssh
  • drag the file from left to right
  • after successful copy, rename the file, id_rsa.pub, to authorized_keys;
  • if the authorized_keys file already exists then need to append the content of id_rsa.pub, to authorized_keys by right clicking each file to open it using the built-in editor, and copy & paste the content.
  • Note: on the debian linux host, the key can be copied directly from the local to remote host using:

    ssh-copy-id pi@raspberrypi.local
    

• Now, SSH client (putty) and SCP client (WinSCP) can be setup to connect without using username/password

Source:

• SSH without password
• Setting up ssh keys on RPi

Increase Swap Space

Increasing swap space is commonly done prior to compilation of native code, such as C/C++, to prevent compilation hanging due to out of memory especially in the multi-core complation setup.

Instructions:

• Swap file is defined in /etc/dphys-swapfile; edit the CONF_SWAPSIZE variable in this file:

  # default value
  #CONF_SWAPSIZE=100
  
  # increase to 1024MB or 2048MB, for example
  CONF_SWAPSIZE=1024
  

• Restart the service

  sudo /etc/init.d/dphys-swapfile stop
  sudo /etc/init.d/dphys-swapfile start
  

• Now ready for memory intensive task such as multi-core compilation;

  # running four cores
  make -j4
  
  # running single core
  make
  

Source: How to change Raspbian swapfile size

Mount USB Drive

Tasks related to mounting USB drive include:

• format the drive
• mount the drive
• unmount

Ref: https://www.raspberrypi.org/documentation/configuration/external-storage.md

Format USB drive

Instructions:

• Identify which device is the USB stick by removing it (if it is plugged in) and then reconnect it. This will generate some messages about the device in the system messages file. View the last few lines to identify your device.
  The USB device will be named something like sda, sdd, etc.

  cat /var/log/messages | tail -n 50
  

  Unnless there are other usb drives, it should be /dev/sda

• RPi will automatically mount USB drive

  cd /media
  ls -al usbdisk
  

• Check the partition on the USB disk using fdisk command

  sudo fdisk /dev/sda
  

  Output:

  Welcome to fdisk (util-linux 2.33.1).
  Changes will remain in memory only, until you decide to write them.
  Be careful before using the write command.
  
  
  Command (m for help):
  

• Enter p to see all the partitions that already exist

  Disk /dev/sda: 57.9 GiB, 62176362496 bytes, 121438208 sectors
  Disk model: Ultra Fit
  Units: sectors of 1 * 512 = 512 bytes
  Sector size (logical/physical): 512 bytes / 512 bytes
  I/O size (minimum/optimal): 512 bytes / 512 bytes
  Disklabel type: dos
  Disk identifier: 0x00000000
  
  Device     Boot Start       End   Sectors  Size Id Type
  /dev/sda1       21952 121438207 121416256 57.9G  c W95 FAT32 (LBA)
  
  Command (m for help):
  

• Delete all the partitions by entering d

  Selected partition 1
  Partition 1 has been deleted.
  
  Command (m for help):
  

• Create new partition and use the USB drive as a single partition by typing n and follow the output below:

  Partition type
     p   primary (0 primary, 0 extended, 4 free)
     e   extended (container for logical partitions)
  Select (default p):
  

  • press enter to accept “p” as primary, and the output:

    Partition number (1-4, default 1):
    

  • press enter to accept single partition, and the output:

    First sector (2048-121438207, default 2048):
    

  • press enter to accept the default 2048, and the output:

    Last sector, +/-sectors or +/-size{K,M,G,T,P} (2048-121438207, default 121438207):
    

  • press enter to accept the default 121438207, and the output:

    Created a new partition 1 of type 'Linux' and of size 57.9 GiB.
    
    Command (m for help):
    

  • enter w to write the new partition table and exit fdisk

• Create a filesystem using the mkfs command

  • Note:
    • vfat file system enable to use the USB drive on a PC or a Mac too, BUT cannot change permission once mounted
    • ext4 is a new filesystem that has become the defacto standard of most Linux distros today
    • ext3 is just ext2 with journal
  • There is one partition, so must put the partition number to the end of the device name:

    sudo mkfs.ext4 /dev/sda1
    

  • To be clean, physically eject the drive and then re-insert it

  • Next mount the drive as described below

Source:
Formatting and Mounting a USB Drive from a Terminal Window

Mount USB flash drive

Raspbian OS will auto-mount USB flash drive soon after it is plugged-in. It will be mounted on /media/<??>.

To change to a different mount point Instructions:

• create a mount point

  sudo mkdir /media/usbdisk
  

• make pi the owner and group if not already

  sudo chown -R pi:pi /media/usbdisk
  

• mount the usb drive to /media/usbdisk mount point

  sudo mount /dev/sda1 /media/usbdisk -o uid=pi,gid=pi
  

Setup to auto-mount after reboot The mount point will not persist after reboot so auto-mount needs to be setup.

• find the UUID for sda1, if the first usb

  ls -l /dev/disk/by-uuid/
  

  Example output with the UUID=0116-FA8D:

  total 0
  lrwxrwxrwx 1 root root 10 Nov 18 13:49 0116-FA8D -> ../../sda1
  lrwxrwxrwx 1 root root 15 Nov 18 13:49 0C61-73F5 -> ../../mmcblk0p1
  lrwxrwxrwx 1 root root 15 Nov 18 13:49 43f2d0bb-83be-464f-94d0-9a751f376c64 -> ../../mmcblk0p2
  

• edit /etc/fstab

  sudo nano /etc/fstab
  
  # add at the end
  UUID=0116-FA8D /media/usbdisk vfat auto,nofail,noatime,users,rw,uid=pi,gid=pi 0 0
  

  Note:

  • Use UUID rather than the device node (/dev/sda1) as the device node can change across reboots especially if drives are added or removed.
  • Include “nofail” in the mount options to prevent the Pi hanging if it is booted without the drive attached.

Unmount USB Drive

sudo umount /media/usbdisk

Additional References

• Adding an External Disk to a Raspberry Pi and Sharing it Over the Network covers how to share the mounted disk across network using protocols: NFS, AFS, and SMB.

Statup Script

Startup scripts perform auto start of: command, application or services after boot. This is useful for powering up RPi headless and without additional user intervention. Headless RPi is access using ssh.

There are three mechanisms to invoke startup scripts after boot:

• rc.local rc.local has drawbacks: not all programs will run reliably, because not all services may be available when rc.local runs. Stretch and Buster use systemd.

• systemd this is a system service that can be start/stop enable/disable from the linux prompt. For more information: systemd, man systemctl, What is an init System

• cron Cron is a tool for configuring scheduled tasks on linux systems. It is used to schedule commands or scripts to run periodically and at fixed intervals. Tasks range from backing up the user’s home folders every day at midnight, to logging CPU information every hour.

Example

Assume there is a python script, push_hold_shut.py, in the home directory.

sudo nano /etc/rc.local
# add the program
~/push_hold_shut.py &

Install Touchscreen Keyboard - Matchbox

Prerequisite:

• Raspbian desktop image (not lite)

• Install

  sudo apt-get update
  sudo apt-get dist-upgrade
  sudo apt-get install --no-install-recommends matchbox-keyboard
  

• The keyboard can be started from Menu > Accesories > Keyboard

Source: Matchbox Keyboard - Raspberry Pi Touchscreen Keyboard

Backup Raspbian microSD

RPI OS runs on microSD card which has a shorter lifetime than, for example, physical hard drive. Therefore, backing up the entire microSD card to a file (.img file) is highly recommended to prevent failure at the least desired time, like in a middle of critical half-finished project.

For Windows, use Win32DiskImager

Source: Win32DiskImager

Connect to RPi

SSH using Putty and PuttyGen Key Generator

Putty is a free SSH client that can be downloaded from here

Instructions:

• Start putty; the main screen is the “PuTTY Configuration” window.
• Enter “Host Name (or IP address)”
• Click SSH radio button for “Connection type”
• Use default Port=22
• Enter a session name to save the configuration
• [Optional] setup SSH key for connection without username/password
  • Click Connection - Data; enter “Auto-login username” with the username to login to RPi; for example, pi
  • Click Connection - SSH - Auth, on the “Private key file for authentication” browse to find the private key in the putty ppk format. Otherwise, jump to the next step to convert the OpenSSH private key (id_rsa) to putty ppk format using the PuttyGen application.
  • To save, click Session, then click Save to save the setup into the session config file for later reuse.
• [Optional] Convert the private key, id_rsa to putty ppk format; both the ssh client (putty) and the scp client (WinSCP) that we will use later to connect to headless RPi need the putty ppk format.
  • as part of putty ssh client installation, the “puttyGen” key generator is also installed; use the puttygen to convert the private key to ppk format
  • Open puttygen
  • On the top menu, click “Conversions” and then “Import”
  • Select the private key (e.g., id_rsa); enter the “Key passphrase” and “Confirm passphrase” fields if provided when generating the key,
  • go to File and click “Save private key” to save the key to disk in PuTTY format (as a .ppk file)

SCP - Secure Copy

Use SCP to tranfer file from a computer or laptop to RPi. The SCP client application needs to be installed on the laptop.

Example, to copy file domain.crt to RPi host 192.168.1.134 for pi user and store it at the home directory:

scp domain.crt pi@192.168.1.134:

For Windows computer, download and setup the free Windows SCP Instructions:

• Open WinSCP
• On the “Session”
  • File Protocol = SCP
  • Host name:
  • Port: 22
  • User name:
  • Password:
• Setup Tunnel otherwise WinSCP will fail to connect and it will keep trying and slowing down the computer network;
  • Click Edit to enable “Advanced” button; in the “Advanced Site Settings”;
  • On the left-hand nav, click Connection - Tunnel, setup the following:
  • Check “Connect through SSH tunnel”
  • Enter hostname, port, username and password
• [Optional] Setup SSH key for connection without username/password
  • Click Edit to enable “Advanced” button; in the “Advanced Site Settings”;
  • On the left-hand nav, click SSH - Authentication, setup the following:
  • Enter the “Authentication parameters” - “Private key file” (id_rsa.ppk or id_rsa); WinSCP needs Putty formatted private key, id_rsa.ppk, but it will take and convert the OpenSSH id_rsa private key file to the Putty format automatically.
  • On the left-hand nav, click Connection - Tunnel, setup the following:
  • Enter the “Tunnel authentication parameters” - “Private key file”; enter the id_rsa.ppk file, the same one used for the authetntication above
  • click OK
• Click “Save”

Source: Secure Copy

Other methods to connect to RPi

• Connect Your Headless Pi to a Library WiFi Network
  • Need USB-to-Serial cable, and know how to connect to RPi serial pins;
  • need to preinstall command line browser w3m
  • need wifi ssid and passphrase (if not public); otherwise scan the ssid after making serial connection to RPi as discussed below;
  • after boot, use putty to connect serial to RPi
  • [optional] scan for wifi ssid

    sudo iwlist wlan0 scan
    

  • connect to wifi; use raspi-config if it works on the putty serial terminal, otherwise modify the wifi config file, /etc/wpa_supplicant/wpa_supplicant.conf to add additional wifi network and restart the wifi or reboot RPi:

    network={
      ssid="<replace_with_ssid>"
      key_mgmt=NONE
      scan_ssid=1
      id_str="networkName"
    }
    

  • to run w3m to accept wifi terms of use

    w3m https://www.google.com/
    

  • find the assigned ip address to RPi, so that can connect using ssh
  • if all goes well, disconnect the serial connection and continue working with ssh terminal
• Connect to laptop Mobile hotspot
  • Need USB-to-Serial cable, and know how to connect to RPi serial pins;
  • On Windows 10 - Search, type network status, and select the match to open the “Network Status” screen
  • on the left navigation, select Mobile hotspot
  • on the “Mobile hotspot” screen, slide to “on” the “Share my internet connection with other devices”
  • feel free to revise the network name if too long or complicated
  • also feel free to revise the auto-generated password
  • on the RPi, use raspi-config to connect to the wifi; the wifi info will be saved to the wifi config file, /etc/wpa_supplicant/wpa_supplicant.conf
  • [alternative] modify the wifi config file, /etc/wpa_supplicant/wpa_supplicant.conf to add additional wifi network and restart the wifi or reboot RPi:

    network={
      ssid="<replace_with_ssid>"
      key_mgmt=NONE
      scan_ssid=1
      id_str="networkName"
    }
    

Useful commands

- Info

info

Output:

File: dir,      Node: Top,      This is the top of the INFO tree.

This is the Info main menu (aka directory node).
A few useful Info commands:

  'q' quits;
  'H' lists all Info commands;
  'h' starts the Info tutorial;
  'mTexinfo RET' visits the Texinfo manual, etc.

* Menu:

Basics
* Common options: (coreutils)Common options.
* Coreutils: (coreutils).       Core GNU (file, text, shell) utilities.
* Date input formats: (coreutils)Date input formats.
* File permissions: (coreutils)File permissions.
                                Access modes.
* Ed: (ed).                     The GNU line editor
* Finding files: (find).        Operating on files matching certain criteria.
[...]

- Disk Usage

Disk usage; -h - human readable; -s - summary;

du -hs

Output:

48k

Disk Free

df -h

Output:

Filesystem      Size  Used Avail Use% Mounted on
/dev/root        30G  1.4G   27G   5% /
devtmpfs        428M     0  428M   0% /dev
tmpfs           433M     0  433M   0% /dev/shm
tmpfs           433M  5.9M  427M   2% /run
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
tmpfs           433M     0  433M   0% /sys/fs/cgroup
/dev/mmcblk0p1  253M   52M  201M  21% /boot
tmpfs            87M     0   87M   0% /run/user/1000

- RAM Usage

State of memory

free -h

Output

              total        used        free      shared  buff/cache   available
Mem:          864Mi        50Mi       740Mi       5.0Mi        74Mi       758Mi
Swap:          99Mi          0B        99Mi

Note: increase swap space

Cloud hosting of RPi

Cloud hosting of Raspberry Pi at: Mythic Beast

Troubleshooting

[Issue] Installing numpy

Installation of Error:

sudo apt update
pip3 install numpy
python3
>>> import numpy
Traceback (most recent call last):
[...]
ImportError: libf77blas.so.3: cannot open shared object file: No such file or directory

Setup:

• raspbian stretch (2019-04-08-raspbian-stretch)
• fresh install + docker (19.03.1, build 74b1e89)

Resolution:

pip3 uninstall numpy
sudo apt install libatlas3-base
sudo pip3 install numpy

Reference:

• Issue installing numpy python3