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