🔁 Restarting My Active Directory Lab 1.0 After a Critical YAML Failure

Over the past few weeks, I’d been building out Active Directory Lab 1.0, modeled on MYFDIR’s tutorial, using VirtualBox to simulate a real-world network environment for cybersecurity practice.

✅ Progress Before the Breakdown

I successfully completed the first two parts of the lab:

  • Installed Windows Server 2019 as DC1 and promoted it to domain controller for adlab.local
  • Joined a Windows 10 VM to the domain and created basic user accounts
  • Created Organizational Units (OUs) and applied simple Group Policy Objects (GPOs)
  • Verified basic domain login and ping connectivity between machines

Everything was working as expected — until I attempted to add a Ubuntu Server 22.04 VM to host Splunk.

🧨 The Failure: Irrecoverable YAML Configuration Error

While configuring Ubuntu’s network settings using netplan, I edited the 00-installer-config.yaml file to assign a static IP and point DNS to the domain controller.

A single spacing or indentation error in YAML broke the config, and the server lost DNS and network access.

Despite hours of troubleshooting, I could not recover:

  • I attempted to validate and reformat the YAML multiple times
  • Tried every fix I could find using ChatGPT, GitHub Copilot, and even YAML linters
  • Restarted networking, edited boot files, changed adapter modes — nothing worked

Eventually, the Splunk server became unrecoverable.

🧹 Full Reset: Nuking the Environment

At that point, I made the decision to start over completely.

  • 🔻 Uninstalled Oracle VirtualBox
  • 🗑️ Deleted all VMs and ISO files (Windows Server, Windows 10, Ubuntu)
  • 🧼 Cleared all .vbox configs and network remnants

This reset cleared out the broken foundation and allowed me to rebuild with stability in mind.

📚 Lessons Learned

  • YAML is brittle — one indent can break the entire network config
  • Snapshots are not optional — I now take one before any system change
  • Logs and backup configs matter — keeping clean copies of YAML and system files will save hours
  • Sometimes a hard reset is the right call — no sense troubleshooting a broken base for days

🔄 Next Steps

I’m now restarting AD Lab 1.0 with a clean slate:

  • Reinstalling VirtualBox + Extension Pack
  • Downloading fresh ISOs
  • Rebuilding the domain controller and client
  • Taking snapshots at key milestones
  • Planning to retry the Splunk server — but with caution, backups, and version control

🔗 View the updated lab repository on GitHub
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