bash : install headscale onto Debian

install_headscale.sh

#!/bin/bash -x

function headscale_globals() {
    HEADSCALE_VERSION="0.26.1"
    HEADSCALE_ARCH="amd64"

    HEADSCALE_USER="headscale"      ## DO NOT CHANGE THIS!!!
    HEADSCALE_GROUP="headscale"     ## DO NOT CHANGE THIS!!!
    HEADSCALE_CONFIG=/etc/headscale ## DO NOT CHANGE THIS!!!

    HEADSCALE_CONFIG_EXAMPLE="https://raw.githubusercontent.com/juanfont/headscale/refs/tags/v0.26.1/config-example.yaml"
    HEADSCALE_PUBLIC_IP=$( ip addr | grep 'scope global' | grep -v 'inet 10.' | grep -v 'inet 192.168.' | sed -E 's/[ \t]+/ /g' | cut -d' ' -f 3 | cut -d/ -f1 )
}


function headscale_download() { 
    headscale_globals
    wget -O ~/Downloads/headscale.deb \
        "https://github.com/juanfont/headscale/releases/download/v${HEADSCALE_VERSION}/headscale_${HEADSCALE_VERSION}_linux_${HEADSCALE_ARCH}.deb"
}


function headscale_install_binaries() { 
    [[ -d ~/Downloads ]] || mkdir -p ~/Downloads
    [[ -f ~/Downloads/headscale.deb ]] || headscale_download
    apt install -y ~/Downloads/headscale.deb
}


function headscale_configure() {
    headscale_globals

    [[ -d ${HEADSCALE_CONFIG} ]] || mkdir -p ${HEADSCALE_CONFIG}
    [[ -f ${HEADSCALE_CONFIG}/config-example.yaml ]] || wget -O ${HEADSCALE_CONFIG}/config-example.yaml ${HEADSCALE_CONFIG_EXAMPLE}
    cat ${HEADSCALE_CONFIG}/config-example.yaml | \
        sed -E "s|^server_url: http://127.0.0.1:|server_url: http://${PUBLIC_IP}:|" | \
        sed -E "s|^# listen_addr: 0.0.0.0:|listen_addr: 0.0.0.0:|" | \
        sed -E "s|^listen_addr: 127.0.0.1:|# listen_addr: 127.0.0.1:|" | \
            tee ${HEADSCALE_CONFIG}/config.yaml > /dev/null
    chown -R ${HEADSCALE_USER}:${HEADSCALE_GROUP} ${HEADSCALE_CONFIG}
}


function headscale_start_service() {
    sudo systemctl enable  --now headscale
    sudo systemctl restart headscale
    sudo systemctl status  headscale
}


function headscale_uninstall() {
    sudo systemctl disable headscale
    sudo systemctl stop headscale
    apt remove --purge -y headscale tailscale
    sudo rm -r -f /var/lib/headscale /var/lib/tailscale /etc/headscale ~/.headscale
    sudo userdel headscale
}


function headscale_install() {
    headscale_install_binaries && headscale_configure && headscale_start_service
}