Enhancement: Backup management service built on top of virtnbdbackup

#Enhancement / Feature Request: External orchestration system built on virtnbdbackup (KVM Backup Manager)

Hello 👋

I’m using virtnbdbackup as the core backup engine in a larger KVM/QEMU backup orchestration system that I developed.

My project extends virtnbdbackup with a full management stack including:
- Web UI
- Backend API service
- Agent-based execution layer

Project link:
https://github.com/aminhashemi1994/kvm-backup-manager

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## Current integration approach

The system is currently built on top of **virtnbdbackup v2.15** and integrates directly through:

- CLI command execution
- Parsing CLI output
- No modifications to virtnbdbackup core

It works reliably as long as:
- CLI commands remain stable
- Output format remains consistent

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## Enhancement suggestion

While building this system, I noticed virtnbdbackup is effectively being used as a core engine in higher-level orchestration systems.

From an integration perspective, it would be very helpful if future versions considered:

- A stable machine-readable output mode (e.g. optional JSON output)
- Or a clearly defined and versioned CLI output contract for external tooling

This would make it easier to build reliable automation layers on top without depending on text parsing.

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## Question

Is there any recommended or planned approach for supporting external integrations more formally in virtnbdbackup?

I’d be happy to align with any suggested best practices.

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## Notes

- Current compatibility: v2.15
- Integration is fully CLI-based
- Works as long as CLI behavior remains stable

Thanks for your work on virtnbdbackup — it has been a solid foundation for building backup automation in KVM environments.