Sample files to enable wireless on Debian initramfs

a_enable_wireless.sh

#!/bin/sh
# this goes into /etc/initramfs-tools/scripts/init-premount/a_enable_wireless
PREREQ=""
prereqs()
{
    echo "$PREREQ"
}

case $1 in
prereqs)
    prereqs
    exit 0
    ;;
esac

. /scripts/functions

AUTH_LIMIT=30
INTERFACE="wlp5s0"
alias WPACLI="/sbin/wpa_cli -p/tmp/wpa_supplicant -i$INTERFACE "

log_begin_msg "Starting WLAN connection"
/sbin/wpa_supplicant  -i$INTERFACE -c/etc/wpa_supplicant.conf -P/run/initram-wpa_supplicant.pid -B -f /tmp/wpa_supplicant.log

# Wait for AUTH_LIMIT seconds, then check the status
limit=${AUTH_LIMIT}

echo -n "Waiting for connection (max ${AUTH_LIMIT} seconds)"
while [ $limit -ge 0 -a `WPACLI status | grep wpa_state` != "wpa_state=COMPLETED" ]
do
    sleep 1
    echo -n "."
    limit=`expr $limit - 1`
done
echo ""

if [ `WPACLI status | grep wpa_state` != "wpa_state=COMPLETED" ]; then
  ONLINE=0
  log_failure_msg "WLAN offline after timeout"
  panic
else
  ONLINE=1
  log_success_msg "WLAN online"
fi

configure_networking

enable-wireless.sh

# !/bin/sh
# This goes into /etc/initramfs-tools/hooks/enable-wireless
set -e
PREREQ=""
prereqs()
{
    echo "${PREREQ}"
}
case "${1}" in
    prereqs)
        prereqs
        exit 0
        ;;
esac

. /usr/share/initramfs-tools/hook-functions

# CHANGE HERE for your correct modules.
manual_add_modules iwlwifi iwlmvm
copy_exec /sbin/wpa_supplicant
copy_exec /sbin/wpa_cli
copy_file config /etc/initramfs-tools/wpa_supplicant.conf /etc/wpa_supplicant.conf

final_commands.sh

# This is run on the shell
chmod +x /etc/initramfs-tools/scripts/local-bottom/kill_wireless
chmod +x /etc/initramfs-tools/scripts/init-premount/a_enable_wireless
chmod +x /etc/initramfs-tools/hooks/enable-wireless

update-initramfs -k all -u
update-grub

kill_wireless.sh

#!/bin/sh
# this goes into /etc/initramfs-tools/scripts/local-bottom/kill_wireless
PREREQ=""
prereqs()
{
    echo "$PREREQ"
}

case $1 in
prereqs)
    prereqs
    exit 0
    ;;
esac

echo "Killing wpa_supplicant so the system takes over later."
kill `cat /run/initram-wpa_supplicant.pid`

wpa_supplicant.conf

# sample /etc/initramfs-tools/wpa_supplicant.conf
# note that this is independent of the system /etc/wpa_supplicant.conf (if any)
# only add the network you need at boot time. **And keep the ctrl_interface** !!
ctrl_interface=/tmp/wpa_supplicant

network={
    ssid="MyNetwork"
    scan_ssid=1
    psk="network passphrase"
    key_mgmt=WPA-PSK
}

Thanks all for the scripts and improvements thereupon. To make this work on my Raspberry Pi 4 running Debian 13, I additionally needed to

• add the following lines to hooks/enable-wireless:

  manual_add_modules brcmfmac brcmfmac_wcc
  copy_exec /sbin/rfkill
  

• before calling /sbin/iw in init-premount/a_enable_wireless, unblock the wireless device:

  /sbin/rfkill unblock 0
  

This is on top of @morfikov's comments.