provision-ubuntu.sh

#!/bin/bash
set -eux

export DEBIAN_FRONTEND=noninteractive

domain=$(hostname --fqdn)

if [ "$(hostname)" = 'moon-ubuntu' ]; then
    local='moon-ubuntu'
    remote='sun-ubuntu'
    remote_ip='10.2.0.4'
else
    local='sun-ubuntu'
    remote='moon-ubuntu'
    remote_ip='10.1.0.4'
fi

# install node LTS.
# see https://github.com/nodesource/distributions#debinstall
apt-get install -y curl
curl -sL https://deb.nodesource.com/setup_10.x | bash
apt-get install -y nodejs
node --version
npm --version

# add the hello-world user.
groupadd --system hello-world
adduser \
    --system \
    --disabled-login \
    --no-create-home \
    --gecos '' \
    --ingroup hello-world \
    --home /opt/hello-world \
    hello-world
install -d -o root -g hello-world -m 750 /opt/hello-world

# create an hello world http server and run it as a systemd service.
cat >/opt/hello-world/main.js <<EOF
const http = require("http");
const server = http.createServer((request, response) => {
    const serverAddress = request.socket.localAddress;
    const clientAddress = request.socket.remoteAddress;

    response.writeHead(200, {"Content-Type": "text/plain"});
    response.write(\`Hello World from $local!
Server Address: \${serverAddress}
Client Address: \${clientAddress}
\`);
    response.end();
});
server.listen(3000);
EOF
cat >package.json <<'EOF'
{
  "name": "hello-world",
  "description": "the classic hello world",
  "version": "1.0.0",
  "license": "MIT",
  "main": "main.js",
  "dependencies": {}
}
EOF
npm install

# launch hello-world.
cat >/etc/systemd/system/hello-world.service <<'EOF'
[Unit]
Description=Hello World
After=network.target

[Service]
Type=simple
User=hello-world
Group=hello-world
Environment=NODE_ENV=production
ExecStart=/usr/bin/node main.js
WorkingDirectory=/opt/hello-world
Restart=on-abort

[Install]
WantedBy=multi-user.target
EOF
systemctl enable hello-world
systemctl start hello-world
# try it.
sleep .2
wget -qO- localhost:3000

#
# add useful commands to the shell history.

cat >>~/.bash_history <<EOF
wget -qO- $remote_ip:3000
wget -qO- localhost:3000
EOF