Alpine with pre-built applications

Introduction

To simplify maintenance and distribution of the pre-built applications described in the QMTECH XC7Z020 notes, I’ve put together a bootable SD card image based on the lightweight Alpine Linux distribution.

Getting started

Download SD card image zip file.
Copy the contents of the SD card image zip file to a micro SD card.
Optionally, to start one of the applications automatically at boot time, copy its start.sh file from apps/<application> to the topmost directory on the SD card.
Install the micro SD card in the QMTECH XC7Z020 board and connect the power.
Applications can be started from the web interface.

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 QMTECH XC7Z020. When in hotspot mode, the IP address of the QMTECH XC7Z020 board 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 MAC address of the wired interface can be changed by editing the mac.txt file.

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), the QMTECH XC7Z020 board can be accessed as sdr-a8xxxx.local, where a8xxxx are the last 6 characters from the MAC address written on the Ethernet connector.

In the local networks with enabled local DNS, the QMTECH XC7Z020 board can also be accessed as sdr-a8xxxx.

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 a file:

# make SD card writable
rw

# edit start.sh
nano apps/sdr_receiver_hpsdr/start.sh

# make SD card read-only
ro