Part-6: Implement Project Level Start-up scripts and Override it on Google Cloud Platform VM (GCP)

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🔹 What is a Project-Level Startup Script?

A startup script is a script that runs automatically whenever a VM boots.

VM-Level Startup Scripts apply only to the specific VM.
Project-Level Startup Scripts apply to all VMs within that project by default.

👉 Use Project-Level scripts when you want to enforce common configurations across all your VMs (e.g., install antivirus, logging agents, monitoring agents, etc.).

🛠️ Step 1: Define Project-Level Startup Script

Go to Compute Engine → Settings → Metadata
Click on Edit
Add Metadata Key: startup-script
Add Metadata Value:

#!/bin/bash
sudo apt install -y telnet
sudo apt install -y nginx
sudo systemctl enable nginx
sudo chmod -R 755 /var/www/html
HOSTNAME=$(hostname)
sudo echo "<!DOCTYPE html> <html> <body style='background-color:rgb(250, 210, 310);'> <h1>PROJECT-LEVEL STARTUP SCRIPT Welcome to Latchu@DevOps - WebVM App1 </h1> <p><strong>VM Hostname:</strong> $HOSTNAME</p> <p><strong>VM IP Address:</strong> $(hostname -I)</p> <p><strong>Application Version:</strong> V1</p> <p>Google Cloud Platform - Demos</p> </body></html>" | sudo tee /var/www/html/index.html

🛠️ Step 2: Create a New VM to Test

Go to VM Instances → Create Instance
Name: projectlevel-startuscript-demo
Machine Type: e2-micro
Firewall: Allow HTTP traffic
Leave all other settings as default
Click Create

👉 Once the VM starts, open the external IP in your browser — you should see the custom HTML page deployed by the project level startup script.

🛠️ Step 3: Override Project-Level Startup Script

What if you don’t want the project-level script applied to a VM?
Easy — just provide a VM-level startup script, which will override the project-level one.

Create another VM

Name: override-projectlevel-startuscript
Machine Type: e2-micro
Firewall: Allow HTTP traffic
Management → Automation → Startup Script → paste the contents of your custom override-webserver-install.sh

#!/bin/bash
sudo apt install -y telnet
sudo apt install -y nginx
sudo systemctl enable nginx
sudo chmod -R 755 /var/www/html
HOSTNAME=$(hostname)
sudo echo "<!DOCTYPE html> <html> <body style='background-color:rgb(2, 210, 210);'> <h1>OVERRIDE STARTUP-SCRIPT - Welcome to Latchu@DevOps - WebVM App1 </h1> <p><strong>VM Hostname:</strong> $HOSTNAME</p> <p><strong>VM IP Address:</strong> $(hostname -I)</p> <p><strong>Application Version:</strong> V1</p> <p>Google Cloud Platform - Demos</p> </body></html>" | sudo tee /var/www/html/index.html

Click Create

👉 This VM will follow the VM-level script, ignoring the project-level one.