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Startup scripts
We can run our own startup scripts from VM instances to perform automatic actions such as updating the system, and sending notifications and so on.
A startup script is specified using metadata keys through the metadata server and can be applied using the console or gcloud command line:
- Once you have set the default region and zone for your instance, you can provide a startup script using the gcloud command line while creating an instance. The script is provided with a—metadata flag:
gcloud compute instances create example-instance --tags http-server
--metadata startup-script='#! /bin/bash
# Installs apache and a custom homepage
# Go to root directory
sudo su -
# For automatic Updates
apt-get update
# Install apache
apt-get install -y apache2
# Edit index.html file
cat <<EOF > /var/www/html/index.html
<html><body><h1>Hello World</h1>
<p>This page was created from a simple start up script!</p>
</body></html>
EOF'
- For an already running instance, startup scripts can be added using the add-metadata flag as follows. The path can be a URL as well, which means that the script can also be located from a Cloud Storage bucket object:
gcloud compute instances add-metadata example-instance --metadata-from-file startup-script=path/to/file