Startup scripts for automation in GCP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a startup script to a Compute Engine instance metadata.

GCP

gcloud compute instances add-metadata my-instance --metadata startup-script=[1]

Drag options to blanks, or click blank then click option'

A"#!/bin/sh echo Startup script running"

B"#!/bin/bash echo Hello World"

C"#!/bin/bash echo Hello from startup script"

D"#!/bin/bash echo Instance started"

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to quote the script string

Using incorrect shell syntax

The startup script must be a string with a valid shell script. Option C is a common example.

2fill in blank

medium

Complete the code to create a VM instance with a startup script that updates packages.

GCP

gcloud compute instances create my-vm --metadata startup-script=[1]

Drag options to blanks, or click blank then click option'

A"#!/bin/bash sudo apt-get update -y"

B"#!/bin/bash sudo yum update -y"

C"#!/bin/bash sudo pacman -Syu --noconfirm"

D"#!/bin/bash sudo zypper refresh"

Attempts:

3 left

💡 Hint

Common Mistakes

Using package managers not available on the OS

Omitting sudo for commands requiring root

On Debian/Ubuntu systems, the startup script to update packages uses apt-get update.

3fill in blank

hard

Fix the error in the startup script metadata to correctly run a script that installs nginx.

GCP

gcloud compute instances add-metadata web-server --metadata startup-script=[1]

Drag options to blanks, or click blank then click option'

A"#!/bin/bash sudo apt-get install -y nginx"

B"#!/bin/bash sudo apt-get install nginx"

C"#!/bin/bash sudo install nginx -y"

D"#!/bin/bash sudo apt-get install nginx -y"

Attempts:

3 left

💡 Hint

Common Mistakes

Placing -y after the package name

Using incorrect install commands

The correct apt-get install command places the -y flag before the package name to auto-confirm installation.

4fill in blank

hard

Fill both blanks to write a startup script that creates a file and writes text into it.

GCP

#!/bin/bash
echo [1] > /tmp/startup.txt
chmod [2] /tmp/startup.txt

Drag options to blanks, or click blank then click option'

A"Hello from startup script"

B755

C644

D"Startup script ran successfully"

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect permission numbers

Forgetting to quote the text string

The script writes a message to a file and sets permissions to 644 for read/write by owner and read by others.

5fill in blank

hard

Fill all three blanks to create a startup script that updates packages, installs nginx, and starts the service.

GCP

#!/bin/bash
sudo [1] update -y
sudo [2] install -y nginx
sudo systemctl [3] nginx

Drag options to blanks, or click blank then click option'

Aapt-get

Byum

Cstart

Dstop

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing package managers

Using systemctl stop instead of start

The script uses apt-get to update and install nginx, then starts the nginx service.

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