This is a small howto about changing the swap file size on a Raspberry Pi which runs with a raspbian operating system.
The swap file size is configured in the /etc/dphys-swapfile file. By default its size is 100 MB. To change that set the CONF_SWAPSIZE value to something else. Here I chanted it to 500 MB:
CONF_SWAPSIZE=500Now the dphys-swapfile.service service needs to be reloaded:
For my recend DIY project I had to configure my Raspberry Pi (3 Model B+) to boot from a USB stick. Here are the configuration instructions.
Open the /boot/config.txt file in a text editor. This is the file on the currently used SD card. Add the following two lines:
program_usb_boot_mode=1
program_usb_boot_timeout=1This enables boot via USB and extends the timeout to wait a little longer for the USB device.
After mounting the GPIO hammer headers to my RPi Zero I am now ready to do some prototyping. The first thing I wanted to test is controlling a 4 pin PWM fan. So here is a short howto on that.
Besides a RPi Zero with pin headers you need a 4 pin PWM (Pulse With Modulation) fan. I took a Noctua NF-F12 5V fan. Be aware that when you take a 12V fan it will damage your board!
To easily access the RPi Zero during setup I use an USB to serial adapter cable as described in on of my other posts.
Prepare the SD card as usually. Usually before mounting an RPi Zero I put it into my Raspberry Pi 3 B+. Since that one has an ethernet connection I can update the system and install required libraries:
This short article describes how to connect and use a DHT22 temperature and humidity sensor on a Raspberry Pi.
I bought a sensor kit from AZ-Delivery. It is easy connect as no soldering work is required. In case you need more details they offer a free DHT22 ebook download.
Note that in their ebook they recommend to use the Adafruit_DHT library. Since that one is deprecated you need to use the CircuitPython-DHT library instead. Details below.
Sometimes it is necessary to access a Raspberry Pi via a serial connection. Especially on a Raspberry Pi Zero which has no ethernet port. This short article explains how to enable a serial connection and how to use it.
First you need a connection cable. I use a USB to serial cable with a PL-2303 chip (Amazon link).
If you plan to connect to your Pi from a Mac you probably need to install a driver, first. The guys at mac-usb-serial.com offer a very good PL-2303 driver for a small price. Download and install it. They also offer a Serial Detect tool which you can use to first test whether your USB serial adapter has been found by the system.
The goal of this article is to explain how to install one or many Raspberry Pi 3 B+ devices connected with one to four Raspberry Pi Zero 1.3 devices each via USB OTG networking.
Each device - Pi and Zero - will be connected to the network 192.168.0.0/24. Each Zero will be connected via USB OTG to the Pi. That will establish a network between the two devices. On each Pi a network bridge will be configured to forward the traffic between the Pi ethernet port and the connected USB ports.
Their individual hostname/IP pattern will be:
10.lab | 192.168.0.10 (1st Pi)
20.lab | 192.168.0.20 (2nd Pi)This is about how I setup and use GnuPG for signing and encrypting data as well as for authenticating SSH sessions. I use both, a YubiKey (4 and 5 NFC) and a GnuPG smartcard from ZeitControl to have a backup in my wallet. As a smartcard reader I use the uTrust 2700 R which works quite well.
My typical use cases are SSH authentication, secure file exchange via public places and signing Git commits. I rarely use GnuPG for email communication. And I neither sign other GnuPG user IDs nor participate in the WOT.
Since there is no difference between setting up a YubiKey or a smartcard the following description mentions the GnuPG smartcard only.
**The following steps should be done on an