In GCP, you can clone a Compute Engine instance by creating an instance from a snapshot or custom image of the boot disk of the existing instance. Below are the steps for each method:

1. Using GCP Console:

Creating a Snapshot/Image:

a. Go to the GCP Console: https://console.cloud.google.com/

b. Navigate to Compute Engine > Snapshots or Compute Engine > Images.

c. Click the “Create Snapshot” or “Create Image” button.

d. Select the source disk from the existing instance.

e. Configure the snapshot or image settings such as name and location.

f. Click “Create” to create the snapshot or image.

Creating a new Instance:

a. Navigate to Compute Engine > VM instances.

b. Click the “Create Instance” button.

c. Configure the instance settings such as name, zone, and machine type.

d. Under “Boot disk,” click “Change” and select the “Custom images” or “Snapshots” tab.

e. Choose the snapshot or custom image created earlier and click “Select.”

f. Configure the remaining settings as needed and click “Create” to create the new instance.

2. Using gcloud CLI:

Creating a Snapshot/Image:

a. Install the Google Cloud SDK and configure authentication: https://cloud.google.com/sdk/docs/install

b. Create a snapshot or custom image using the gcloud compute disks snapshot or gcloud compute images create command:

gcloud compute disks snapshot SOURCE_DISK --snapshot-names SNAPSHOT_NAME --zone ZONE

or

gcloud compute images create IMAGE_NAME --source-disk SOURCE_DISK --source-disk-zone ZONE

Replace SOURCE_DISK, SNAPSHOT_NAME, IMAGE_NAME, and ZONE with appropriate values.

Creating a new Instance:

a. Create a new instance from the snapshot or custom image using the gcloud compute instances create command:

gcloud compute instances create INSTANCE_NAME --image-family IMAGE_FAMILY --image-project IMAGE_PROJECT --zone ZONE

Replace INSTANCE_NAME, IMAGE_FAMILY, IMAGE_PROJECT, and ZONE with appropriate values.

3. Using Terraform:

Creating a Snapshot/Image:

a. Update the main.tf file to create a snapshot or custom image of the boot disk of the existing instance:

resource "google_compute_disk_snapshot" "example_snapshot" {
  name   = "example-snapshot"
  zone   = "us-central1-a"
  source_disk = "SOURCE_DISK"
}

# OR

resource "google_compute_image" "example_image" {
  name   = "example-image"
  family = "example-family"
  source_disk = "SOURCE_DISK"
  source_disk_zone = "us-central1-a"
}

Replace SOURCE_DISK with the appropriate value.

b. Run the following commands to apply the changes:

terraform init
terraform plan
terraform apply

Creating a new Instance:

a. Update the main.tf file to create a new instance from the snapshot or custom image:

resource "google_compute_instance" "example_clone" {
  name         = "example-instance-clone"
  machine_type = "n1-standard-1"
  zone         = "us-central1-a"

  boot_disk {
    initialize_params {
      snapshot = google_compute_disk_snapshot.example_snapshot.self_link
      # OR
      image = google_compute_image.example_image.self_link
    }
  }

  # ... other settings ...
}

b. Run the following commands to apply the changes:

terraform init
terraform plan
terraform apply