Alpine with pre-built applications

Introduction

To simplify maintenance and distribution of the pre-built applications described in the Red Pitaya notes, I’ve put together a bootable SD card image based on the lightweight Alpine Linux distribution.

Getting started

The default password for the root account is changeme.

Network configuration

Wi-Fi is by default configured in hotspot mode with the network name (SSID) and password both set to RedPitaya. When in hotspot mode, the IP address of Red Pitaya is 192.168.42.1.

The wired interface is by default configured to request an IP address via DHCP. If no IP address is provided by a DHCP server, then the wired interface falls back to a static IP address 192.168.1.100.

The configuration of the IP addresses is in /etc/dhcpcd.conf. More information about /etc/dhcpcd.conf can be found at this link.

From systems with enabled DNS Service Discovery (DNS-SD), Red Pitaya can be accessed as rp-f0xxxx.local, where f0xxxx are the last 6 characters from the MAC address written on the Ethernet connector.

In the local networks with enabled local DNS, Red Pitaya can also be accessed as rp-f0xxxx.

Useful commands

The Alpine Wiki contains a lot of information about administrating Alpine Linux. The following is a list of some useful commands.

Switching to client Wi-Fi mode:

# configure WPA supplicant
wpa_passphrase SSID PASSPHRASE > /etc/wpa_supplicant/wpa_supplicant.conf

# configure services for client Wi-Fi mode
./wifi/client.sh

# save configuration changes to SD card
lbu commit -d

Switching to hotspot Wi-Fi mode:

# configure services for hotspot Wi-Fi mode
./wifi/hotspot.sh

# save configuration changes to SD card
lbu commit -d

Changing password:

passwd

lbu commit -d

Installing packages:

apk add python3

lbu commit -d

Editing WSPR configuration:

# make SD card writable
rw

# edit decode-wspr.sh
nano apps/sdr_transceiver_wspr/decode-wspr.sh

# make SD card read-only
ro