Azure xplat-cli @ GitHub

All Azure features are available via REST APIs.
Usual access to them is from portals ("classic" and "new"), as well from PowerShell from Windows.
There is a "cross-platform" open source tool xplat-cli based on Node.js, that can run on all major OSs.

Azure/azure-xplat-cli: Microsoft Azure Cross Platform Command Line @ GitHub
Features:

• Accounts Management
• Azure Service Management
  • Storage
  • Websites
  • Virtual machines
  • Network
  • Mobile Services
  • Service Bus
  • SQL Database
• Azure Resource Management
  • Generic resource groups and deployments management
  • Role based access control
  • Cmdlets for individual resource providers, including compute, storage, network, redis cache, insights, etc
  • Datalake
• Key Vault

Install the Azure Command-Line Interface | Microsoft Azure

Use the Azure CLI with Service Management | Microsoft Azure

Using the Azure CLI with Azure Storage | Microsoft Azure

Use the Azure CLI with Resource Manager | Microsoft Azure