Startup scripts for automation in GCP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

Startup Script Execution Timing on GCP VM

You add a startup script to a Google Compute Engine VM instance metadata to install software on boot. When exactly does this script run?

A Only once, the very first time the VM boots after creation.

B Every time the VM boots or restarts.

C Only when the VM is stopped and then started again, not on reboot.

D Only when the VM is manually triggered to run the script via SSH.

💡 Hint

Think about when startup scripts are designed to automate setup.

Startup scripts run every time the VM boots or restarts, ensuring the setup steps are applied on each boot.

❓ Configuration

intermediate

Correct Metadata Key for GCP Startup Script

Which metadata key must you use to add a startup script that runs on a Google Compute Engine VM instance?

A startup-script

B user-data

C init-script

D boot-script

💡 Hint

Check the official GCP documentation for the exact metadata key name.

The correct metadata key for startup scripts on GCP VM instances is 'startup-script'.

❓ security

advanced

Security Risk of Startup Scripts in GCP

What is a major security risk when using startup scripts on GCP VM instances?

A Startup scripts can expose sensitive data if they contain secrets in plain text.

B Startup scripts always run with limited permissions, so they cannot modify system files.

C Startup scripts are encrypted by default, so there is no risk of exposure.

D Startup scripts cannot access network resources, so they pose no security risk.

💡 Hint

Consider what happens if secrets are stored directly in scripts.

Storing secrets like passwords or API keys in plain text inside startup scripts can expose them to anyone with access to the metadata or VM.

❓ Architecture

advanced

Automating Software Installation with Startup Scripts

You want to ensure a custom monitoring agent is installed and running on all new VM instances automatically. Which approach best uses startup scripts for this?

A Manually SSH into each VM after creation and run the installation commands.

B Use a firewall rule to block all traffic except monitoring agent ports.

C Create a snapshot of a VM with the agent installed and use it as a base image for new VMs.

D Add a startup script in instance metadata that downloads, installs, and starts the agent on every boot.

💡 Hint

Think about automating installation at boot time without manual steps.

Startup scripts automate installation and startup of software on every boot, ensuring consistency across VMs.

🧠 Conceptual

expert

Effect of Startup Script Failure on VM Boot

If a startup script on a GCP VM instance fails during execution, what is the effect on the VM's boot process?

A The VM boots but disables network interfaces until the script succeeds.

B The VM fails to boot and enters a stopped state automatically.

C The VM continues booting normally; the startup script failure does not stop the boot.

D The VM boots but deletes the startup script from metadata automatically.

💡 Hint

Consider how startup scripts relate to the VM's core boot process.

Startup scripts run after the VM boots; failure in the script does not prevent the VM from booting.

Practice

1. What is the main purpose of a startup script in a Google Cloud VM instance?

easy

A. To automate tasks when the VM boots

B. To manually start the VM

C. To create a new VM instance

D. To delete files from the VM

Solution

1. Step 1: Understand startup script role

   Startup scripts run automatically when a VM starts to perform tasks without manual intervention.

2. Step 2: Identify correct purpose

   Among the options, only automating tasks at boot matches the startup script function.

3. Final Answer:

   To automate tasks when the VM boots -> Option A

4. Quick Check:

   Startup script = automate tasks at boot [OK]

Hint: Startup scripts run automatically at VM boot time [OK]

Common Mistakes:

• Confusing startup scripts with manual commands
• Thinking startup scripts create or delete VMs
• Assuming startup scripts run after user login

2. Which command correctly adds a startup script to a new VM instance using gcloud CLI?

easy

A. gcloud compute instances create my-vm --metadata startup='echo Hello'

B. gcloud compute instances create my-vm --script-startup='echo Hello'

C. gcloud compute instances create my-vm --startup='echo Hello'

D. gcloud compute instances create my-vm --metadata startup-script='echo Hello'

Solution

1. Step 1: Recall correct flag for startup script

   The correct metadata key to add a startup script is 'startup-script'.

2. Step 2: Match command syntax

   gcloud compute instances create my-vm --metadata startup-script='echo Hello' uses '--metadata startup-script' correctly; others use invalid flags.

3. Final Answer:

   gcloud compute instances create my-vm --metadata startup-script='echo Hello' -> Option D

4. Quick Check:

   Use --metadata startup-script to add scripts [OK]

Hint: Use --metadata startup-script flag with gcloud create [OK]

Common Mistakes:

• Using incorrect flag names like --script-startup
• Confusing metadata keys with other flags
• Missing quotes around the script content

3. Given this startup script added to a VM:

#!/bin/bash
echo "Hello World" > /var/log/startup.log

What will happen when the VM boots?

medium

A. The VM will fail to boot due to script error

B. The file /var/log/startup.log will contain 'Hello World'

C. Nothing happens because echo is not allowed

D. The file /var/log/startup.log will be deleted

Solution

1. Step 1: Analyze the script commands

   The script writes the text 'Hello World' into the file /var/log/startup.log using echo and redirection.

2. Step 2: Understand script effect on boot

   Since startup scripts run as root, the file will be created or overwritten with the text.

3. Final Answer:

   The file /var/log/startup.log will contain 'Hello World' -> Option B

4. Quick Check:

   Startup script writes text to log file [OK]

Hint: Startup scripts run as root and can write files [OK]

Common Mistakes:

• Assuming echo command is blocked
• Thinking the file will be deleted instead of created
• Believing the VM will fail due to simple echo

4. You wrote this startup script:

#!/bin/bash
apt-get update
apt-get install nginx -y

But nginx is not installed after VM boots. What is the likely problem?

medium

A. The script lacks 'sudo' before commands

B. The script is missing the shebang line

C. The script runs before network is ready

D. The script should use 'yum' instead of 'apt-get'

Solution

1. Step 1: Check script commands and environment

   The script uses apt-get which requires network access to update and install packages.

2. Step 2: Identify timing issue

   Startup scripts may run before network is fully ready, causing apt-get to fail silently.

3. Final Answer:

   The script runs before network is ready -> Option C

4. Quick Check:

   Network must be ready before package install [OK]

Hint: Ensure network is ready before package installs in startup scripts [OK]

Common Mistakes:

• Adding sudo unnecessarily (scripts run as root)
• Ignoring network readiness in startup timing
• Using wrong package manager for Debian-based VM

5. You want to automate VM setup to install Apache, create a website folder, and start the service on boot. Which startup script snippet correctly achieves this?

hard

A. #!/bin/bash
apt-get update
apt-get install apache2 -y
mkdir /var/www/html
systemctl enable apache2
systemctl start apache2

B. #!/bin/bash
apt-get install apache2
mkdir /var/www/html
service apache2 stop

C. #!/bin/bash
apt-get update
apt-get install apache2 -y
mkdir -p /var/www/html
systemctl start apache2

D. #!/bin/bash
yum update -y
yum install apache2 -y
mkdir /var/www
systemctl restart apache2

Solution

1. Step 1: Verify package manager and commands

   For Debian-based VMs, apt-get is correct. Apache package is apache2. Creating /var/www/html is needed.

2. Step 2: Check service management commands

   #!/bin/bash apt-get update apt-get install apache2 -y mkdir /var/www/html systemctl enable apache2 systemctl start apache2 uses 'systemctl enable' to start Apache on boot and 'systemctl start' to start immediately, which is best practice.

3. Step 3: Compare other options

   #!/bin/bash apt-get update apt-get install apache2 -y mkdir -p /var/www/html systemctl start apache2 misses enabling service on boot. #!/bin/bash apt-get install apache2 mkdir /var/www/html service apache2 stop stops service instead of starting. #!/bin/bash yum update -y yum install apache2 -y mkdir /var/www systemctl restart apache2 uses yum (wrong for Debian).

4. Final Answer:

   #!/bin/bash apt-get update apt-get install apache2 -y mkdir /var/www/html systemctl enable apache2 systemctl start apache2 -> Option A

5. Quick Check:

   Enable and start service for automation [OK]

Hint: Enable and start services to run on boot in startup scripts [OK]

Common Mistakes:

• Forgetting to enable service to start on boot
• Using wrong package manager for the OS
• Stopping service instead of starting it