📌 ** Script 1**

launch_dr_vm_same_project.sh

Purpose

This script launches a Disaster Recovery (DR) VM from a machine image within the same project, but in a different region (e.g., Mumbai → Delhi). Useful for DR drills, region failover, and multi-region resiliency.

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When to use

Use Script-1 when:

• Source project and destination project are same
• VM must be launched in another region of the same project
• VM must be launched using CMEK (Custom KMS encryption)
• Network is hosted in a Shared VPC host project

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Required input details

Input	Example
Project ID	prod-prj-psb59-svc
Machine Image Name	prod-psb59-app-server-gcp-1a-backup-20251118-2030
Host VPC Project ID	prod-prj-host-nw
Network Name	prod-vpc-gcp-opl

Other values (region, zone, subnet, KMS key, service account) are selected automatically via menus.

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What the script does automatically

✔ Lists India regions → user selects ✔ Lists zones in selected region → user selects ✔ Lists only private subnets from Shared VPC → user selects ✔ Lists available CMEK encryption keys → user selects ✔ Lists service accounts → user selects ✔ Adds no external IP automatically → secure DR launch ✔ Creates VM using selected machine image

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Example expected successful output

🎉 SUCCESS — DR VM Created
VM: prod-psb59-app-server-dr-1a  |  Region: asia-south2  |  Zone: asia-south2-a

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Preconditions

Requirement	Status
Machine image exists	Yes
Subnet exists in chosen region	Yes
CMEK key exists in chosen region	Yes
DR service account has encryption access	Yes

No IAM sharing required between projects (because source and dest are same).

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Command to run

chmod +x launch_dr_vm_same_project.sh
./launch_dr_vm_same_project.sh

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📌 Script 2

launch_dr_vm_cross_project.sh

Purpose

This script launches a VM in a different project using a machine image from another project. Example: SIT → QA / QA → UAT / UAT → PROD / PROD → DR.

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When to use

Use Script-2 when:

• Source and destination projects are different
• Machine image is created in Project-A
• VM must be launched in Project-B
• VM must use Destination KMS encryption (CMEK)

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Required input details

Input	Example
Source Project ID	dev-prj-gst-svc-sit
Destination Project ID	dev-prj-gst-svc-qa
Machine Image Name	sit-bob-gst-sahay-app-server-gcp-backup-20250708-2030
Host VPC Project ID	dev-prj-host-nw
Network Name	dev-vpc-gcp-opl

Other values (region, zone, subnet, KMS key, service account) are selected automatically via menus.

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What the script does automatically

✔ Pulls zones from destination project ✔ Pulls private subnets from Shared VPC ✔ Pulls CMEK keys only from destination project ✔ Pulls service accounts only from destination project ✔ Launches instance without public IP

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Cross-Project IAM Requirement (Mandatory)

Before using Script-2, run this only once per source–destination project pair:

gcloud projects add-iam-policy-binding <SOURCE_PROJECT> \
  --member=serviceAccount:<DEST_PROJECT_NUMBER>@cloudservices.gserviceaccount.com \
  --role=roles/compute.imageUser

If this step is missing, VM launch will fail with:

ERROR: Read access to image denied

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Example expected successful output

🎉 SUCCESS — Cross-Project DR VM Created
VM: sit-pabl-java-mig-app-server-gcp | Project: dev-prj-pabl-svc-uat | Region: asia-south1 | Zone: asia-south1-b

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Command to run

chmod +x launch_dr_vm_cross_project.sh
./launch_dr_vm_cross_project.sh

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🔚 Final Comparison Summary

Feature	Script 1	Script 2
Launch in same project	✔	✖
Launch in different project	✖	✔
CMEK encryption	✔	✔
No public IP	✔	✔
Shared VPC support	✔	✔
Needs IAM binding	✖	✔ (only once per pair)

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