connects RPI4 to an access point so that SSH can be accessed directly without cables.

alarmpi-wifi.sh

#!/bin/sh
#https://archlinuxarm.org/forum/viewtopic.php?f=31&t=11529
#dependency: pacman -S wpa_supplicant

set -e

if [ $# -ne 3 ]; then
   echo "Usage: $0 </dev/disk> <ssid> <passphase>"
   exit 1
fi

DISK="$1"
SSID="$2"
PASS="$3"

if [ ! -b "${DISK}" ]; then
   echo "Not a block device: ${DISK}"
   exit 1
fi

if [ "${USER}" != "root" ]; then
   echo "Must run as root."
   exit 1
fi

echo Mounting
if [ ! -d "root" ]; then
   mkdir root
   mount "${DISK}2" root
else
   mount "${DISK}2" root
fi

cat << EOF >> root/etc/systemd/network/wlan0.network
[Match]
Name=wlan0

[Network]
DHCP=yes
MulticastDNS=yes
LLMNR=yes
EOF

wpa_passphrase "${SSID}" "${PASS}" > root/etc/wpa_supplicant/wpa_supplicant-wlan0.conf

ln -s \
   /usr/lib/systemd/system/wpa_supplicant@.service \
   root/etc/systemd/system/multi-user.target.wants/wpa_supplicant@wlan0.service

echo Unmounting
umount root

echo Cleaning up
rmdir root