Connecting to vCenter/ESXi and Retrieving VM Information with PowerCLI and Python

Learning Objectives

By the end of this article, you will:

• Understand how to securely connect to vCenter or ESXi using PowerCLI.
• Retrieve and export virtual machine information in a reusable format.
• Integrate PowerCLI scripts with Python for end-to-end automation.
• Visualize the workflow with a clear diagram.

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My Personal Repository on GitHub

VMware Repository on GitHub

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Prerequisites

• Completed Articles 1 and 2 (PowerCLI and Python are installed).
• Access to a VMware vCenter or standalone ESXi host with valid credentials.
• A Windows system (PowerCLI requires Windows PowerShell).
• Administrative permissions for scripting and export.

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1. The PowerCLI Connection Workflow

To automate VMware, you first need to connect to the environment.
PowerCLI uses the Connect-VIServer cmdlet to establish a secure session with vCenter or ESXi.

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2. Example: PowerShell Script to Connect and Retrieve VM Information

Let’s create a script that:

• Connects to your vCenter/ESXi
• Retrieves a list of all VMs, including their names, power state, guest OS, and IP addresses
• Exports the data to a CSV file

Save this as get_vm_info.ps1:

# Import PowerCLI
Import-Module VMware.PowerCLI

# Disable certificate warnings for test labs (not recommended in production)
Set-PowerCLIConfiguration -InvalidCertificateAction Ignore -Scope Session -Confirm:$false

# Connect to vCenter or ESXi (update credentials)
Connect-VIServer -Server <vcenter-address> -User <username> -Password <password>

# Get VM info: Name, PowerState, Guest OS, IP Address
Get-VM | Select-Object Name, PowerState, @{N="GuestOS";E={$_.Guest.OSFullName}}, @{N="IPAddress";E={$_.Guest.IPAddress -join ', '}} |
    Export-Csv -Path C:\Temp\vm_inventory.csv -NoTypeInformation

# Disconnect when done
Disconnect-VIServer -Server * -Confirm:$false

Replace <vcenter-address>, <username>, and <password> with your details.

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3. Calling the PowerShell Script from Python

Use Python to automate running the PowerShell script:

import subprocess

ps_script = r"C:\Temp\get_vm_info.ps1"

completed_process = subprocess.run([
    "powershell.exe",
    "-ExecutionPolicy", "Bypass",
    "-File", ps_script
], capture_output=True, text=True)

print("Script Output:", completed_process.stdout)
if completed_process.stderr:
    print("Errors:", completed_process.stderr)

This will generate C:\Temp\vm_inventory.csv containing your VM details.

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4. Diagram: End-to-End VM Inventory Automation

Legend:

• Python orchestrates the flow
• PowerShell script runs the actual commands
• PowerCLI interacts with VMware
• Results are exported to CSV

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5. Viewing and Using the VM Inventory Output

Once the script completes, open C:\Temp\vm_inventory.csv with Excel or any CSV viewer.
Each row represents a VM, with columns for Name, PowerState, Guest OS, and IP Address.

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6. Troubleshooting and Best Practices

• SSL/TLS Warnings:
  For test labs, the script disables certificate validation. For production, ensure you use trusted certs.
• Connection Issues:
  Confirm network access and user permissions.
• Output File Not Created:
  Make sure C:\Temp\ exists and you have write access.
• Credential Security:
  Avoid storing passwords in scripts for production. Consider Windows Credential Manager

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7. Further Reading

VMware PowerCLI Documentation:

• VMware PowerCLI Documentation

Python subprocess docs:

• Python subprocess docs

PowerShell Official Docs:

• PowerShell Official Docs

Credential Manager Module:

• Windows Credential Manager

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8. Conclusion and Next Steps

You have learned how to connect to vCenter or ESXi using PowerCLI, retrieve VM inventory, and automate everything with Python.
This workflow forms the foundation for reporting, auditing, and further automation across your VMware estate.

Next up: In Article 4, you will learn how to automate VM lifecycle actions and snapshots, taking your scripting skills to the next level.