sandgreen.dk

Raspberry Pi

A small but growing collection of usefull scripts, tips and one-liners
Someday when I have the time, Ill try to make this list a bit more readable, right now they are just roughly sorted in more or less describing catagories
Most of these commands are not exclusive to RPi but can be used on any Linux distro.

Burning image to SD-card

Show a list of drives and partitions:

sudo fdisk -l

Burn image to sdc:

sudo dd bs=4M if=2018-11-13-raspbian-stretch-lite.img of=/dev/sdc

Show progress (run in separat terminal):

watch grep -e Dirty: -e Writeback: /proc/meminfo

Backup:

sudo dd if=/dev/sdc of=/WHERE_TO_STORE_THE_BACKUP/image_name.img bs=1M

Webserver

Install and setup lighttpd webserver with PHP:

sudo apt install lighttpd

sudo apt install php7.3-common php7.3-cgi php7.3

sudo lighty-enable-mod fastcgi-php

sudo service lighttpd force-reload

sudo chown www-data:www-data /var/www

sudo chmod 775 /var/www

sudo usermod -a -G www-data pi

Create a php file in /var/www/html/ with the following line to test php:

<?php phpinfo(); ?>

Cameras and images

Take picture with camera:

raspistill -w 800 -h 600 -o cam.png

Livefeed from camera:

raspistill -f -t 0

Install fswebcam:

sudo apt install fswebcam

You can take a sample shot with the following command:

fswebcam -r 640x480 --jpeg 85 -D 1 web-cam-shot.jpg

-r = Image resolution:
--jpeg = format type of the image & 85 for its quality standard:
-D = delay set before capture.:

Get image info:

sudo apt install imagemagick

identify image.png

Creating a timalapse-video from a folder of jpeg images
Convert filnames to myfile0000, myfile0001, myfile0002 etc.:

ls *.jpg| awk 'BEGIN{ a=0 }{ printf "mv %s myfile%04d.JPG\n", $0, a++ }' | bash

Convert sequence of JPEG images to MP4 video:

ffmpeg -r 24 -pattern_type glob -i '*.JPG' -i myfile%04d.JPG -s hd1080 -vcodec libx264 timelapse.mp4

-r 24 = output frame rate
-pattern_type glob -i '*.JPG' = all JPG files in the current directory
-i DSC_%04d.JPG = e.g. DSC_0397.JPG
-s hd1080 = 1920x1080 resolution

Crontab

Create a logs directory in home:

mkdir logs

Edit crontab (root):

sudo crontab -e

Choose editor and add the following line at the bottom:

@reboot sh /home/pi/launcher.sh >/home/pi/logs/cronlog 2>&1

View errors:

cd logs

cat cronlog

List for current user:

crontab -l

List for pi user:

crontab -u pi -l

Edit for current user:

crontab -e

Network

Mount pi system on local system:

mkdir /home/sandie/Downloads/raspberry_pi/sshfs/

sshfs pi@192.168.1.42:/ /home/sandie/Downloads/raspberry_pi/sshfs/

Unmount after use:

sudo umount /home/sandie/Downloads/raspberry_pi/sshfs/

ssh pi@192.168.1.76

X11 forwarding:

ssh -Y pi@192.168.1.76

Search for ip in range 192.168.1.0 - 192.168.1.255:

nmap -sn 192.168.1.*

show own ip:

ip addr show

Setting up wifi:

sudo nano /etc/wpa_supplicant/wpa_supplicant.conf

Go to the bottom of the file and add the following:

network={
ssid="YOUR_SSID"
psk="Your_wifi_password"
}

If you want a headless way of doing it, connect the SD card to your pc (most modern distros should automount it), open a terminal window and cd to the boot drive where you can enable ssh by creating an empty file called ssh.

touch ssh

create a wpa_supplicant.conf file to store the wifi connection details on the Pi’s boot drive:

nano wpa_supplicant.conf

Paste the following content in the wpa_supplicant.conf file, adjust it with your wifi details and save it with ctrl + x.:

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

network={
ssid="NETWORK-NAME"
psk="NETWORK-PASSWORD"
}

This will use DHCP to obtain an IP address. Unmount and disconnect the SD card from your computer and put it in the Pi. Connect a power source to the Pi and the boot sequence should begin.

Use a terminal to connect to it over ssh:

ssh pi@192.168.1.123

The default password for the pi-user on a clean Raspbian install is raspberry, this should be changed as the first step.

Use nmap to see all scan for devices og the local net:

nmap -sn 192.168.1.*

Or use ping:

ping raspberrypi.local

To make sure that the RPi can only be found on the local network, use ufw (Uncomplicated Firewall), a minimalist command line tool. This part is essential if the RPi GPIO-pins will be controlled by nc remote

sudo apt-get install ufw

First, deny all incoming connetions to your raspberry pi:

sudo ufw default deny

Second, only allow the local network connections ( In this example I suppose that your local network is 192.168.1.0/24)

sudo ufw allow from 192.168.1.0/24

Finally, enable the ufw typing:

sudo ufw enable

You can see the active rules typing:

sudo ufw status verbose

nc remote

A low security and exposed for short term solutions or behind firewall:

Run on server:

mkfifo /tmp/netfifo; nc -lk 1234 0</tmp/netfifo | bash -e &>/tmp/netfifo

Run on client:

echo "ls" | nc HOST 1234

Set pin mode:

gpio mode 25 out

GPIO 25 on/off:

gpio write 25 1 / gpio write 25 0

Send to RPi examples:

echo "gpio write 25 0" | nc -q 0 192.168.1.84 1234

echo "gpio write 25 1" | nc -q 0 192.168.1.84 1234

turn gpio 25 on, wait 4 sec. and turn off:

echo "gpio write 25 1 && sleep 4 && gpio write 25 0" | nc -q 0 192.168.1.84 1234

gnuplot

Gnuplot is a neat little program that can plot data.
Install gnuplot:

sudo apt install gnuplot

Bacis data file format (temp.dat):

##date time temp_1

23/03/2019 00:00:01 50.2
23/03/2019 00:01:00 55.3
23/03/2019 00:02:00 58.4
23/03/2019 00:03:03 51.5
23/03/2019 00:04:06 52.5
23/03/2019 00:05:12 58.7
23/03/2019 00:06:14 41.8
23/03/2019 00:07:11 31.9
23/03/2019 00:08:01 28.9

Script to run gnuplot (temp.pg):

#!/usr/bin/gnuplot
reset
set terminal png medium size 640,480

set xdata time
set timefmt "%d/%m/%Y %H:%M:%S"
set format x "%H:%M"
set xlabel "time"

set ylabel "temperature"
set yrange [0:101]

set title "RPI temp"
set key reverse Left outside
set grid

set style data lines

plot "temp.dat" using 1:3 lc 2 lw 2 notitle

make file executable:

chmod +x temp.pg

Running the script on a data-file and output to a png:

./temp.pg > temp_graph.png

This should create a nice plot like this:
gnuplot