WSL2 Linux VM networking init

network-start.sh

#!/bin/sh

# https://superuser.com/questions/1582234/make-ip-address-of-wsl2-static/1808525#1808525
# https://superuser.com/a/1723531/433945
# Add to /etc/wsl.conf as boot/command="/root/network-start.sh" for autostart
# (C) 2023-2025 by Jim Klimov (and other SO/GH/blog authors)
#
# This script assigns a fixed IP to the VM, fixes up DNS,
# allows fixed port on host for SSH dial-back into the VM
# and starts the SSH server.

PATH="/mnt/c/WINDOWS/System32/WindowsPowerShell/v1.0:$PATH"
export PATH

# Fenced with a separate touch-file, an IP address might be not
# available when this first runs - allow reentry until success!
# Assumes first IP is the one generated by WSL anew for each VM boot.
AUTOIP="`hostname -I | awk '{print $1}'`"
if [ -n "$AUTOIP" ] && [ ! -f /dev/shm/network-initialized-fwd ] ; then
    powershell.exe -Command "Start-Process netsh.exe -ArgumentList \"interface portproxy add v4tov4 listenport=22099 connectport=22 connectaddress=$AUTOIP\" -Verb RunAs"
    # Consider similar forwards for X11, VNC, etc.
    touch /dev/shm/network-initialized-fwd
fi

# (Optionally) shield the rest of such init (assuming SSHD listens
# on IP_ANY, so starting it once suffices)
[ -f /dev/shm/network-initialized ] && exit

# https://gist.github.com/wllmsash/1636b86eed45e4024fb9b7ecd25378ce
# Custom IP might work or not, based on whims of Windows firewall du-jour
( ip a | grep 172.22.48.99 ) || sudo /usr/sbin/ip addr add 172.22.48.99/255.255.240.0 dev eth0

ps -ef | grep -v grep | grep sshd || sudo service ssh start

# I've also had problems resolving Internet DNS, so this settled in
# (also works if /etc/resolv.conf is a dangling symlink to non-existent
# dir below, by default). Specifically, my problem was having the
# resolver re-generated from Windows host settings, and not having
# VPN etc. access to the domain DNS server to actually resolve stuff.
# Per my notes, https://github.com/microsoft/WSL/issues/6977 might
# also help: /etc/wsl.conf => [network] => generateResolvConf=false
grep 8.8.8.8 /etc/resolv.conf || {
    sudo mkdir -p /run/resolvconf/ && \
    echo 'nameserver 8.8.8.8' | sudo tee -a /etc/resolv.conf
}

if [ ! -f /dev/shm/network-initialized ]; then
    touch /dev/shm/network-initialized
fi