Azure Docs

Understanding Azure Blob Storage Containers

This document provides a comprehensive overview of Azure Blob Storage containers, their purpose, and key concepts.

What is a Container?

A container is a logical grouping of blobs within an Azure Storage account. Think of it like a folder in a traditional file system, but with additional capabilities and properties. Containers provide a way to organize and manage your blobs effectively. Every blob must reside within a container.

Key Characteristics of Containers:

• Namespace: Containers organize blobs and provide a unique namespace within a storage account.
• Access Control: You can control access to blobs by configuring access policies at the container level. This includes public access levels and shared access signatures (SAS).
• Blob Naming: Blob names are unique within a container.
• Metadata: Containers can have associated metadata, which is a collection of key-value pairs that can be used to store custom information about the container.
• REST API: Containers are managed through the Azure Storage REST API, which allows for programmatic interaction.

Container Naming Rules:

Container names must adhere to the following rules:

• Container names must start with a letter or number.
• Container names can only contain lowercase letters, numbers, and hyphens.
• Container names must be between 3 and 63 characters long.
• Container names must end with a letter or number.
• Container names must be formatted as a valid DNS name.
• Container names must be unique within a storage account.

Container Access Levels:

You can define the level of public access for a container. This setting dictates how unauthorized users can access the blobs within the container. The possible access levels are:

• Private: No public access. Access is restricted to authenticated users via their Azure credentials or shared access signatures. This is the default setting.
• Blob: Public read access for blobs only. Anonymous users can read blobs within the container but cannot access container properties or list blobs.
• Container: Public read access for the container and its blobs. Anonymous users can read blobs and list blobs within the container, but they cannot access container properties.

Creating a Container:

Containers are typically created using the Azure portal, Azure CLI, Azure PowerShell, or the Azure Storage SDKs. Here's a conceptual example using Azure CLI:

az storage container create --name <container-name> --account-name <storage-account-name> --account-key <storage-account-key> --public-access blob
                

Example of creating a container with blob public access.

Managing Containers

Once created, containers can be managed to:

• Change access policies.
• Add or retrieve metadata.
• Delete the container and all its contents.
• List blobs within the container.

Example Scenario: Website Hosting

A common use case for public blob access is static website hosting. By setting a container's access level to 'Blob' or 'Container' and configuring it as a static website endpoint, you can serve web content directly from Azure Blob Storage.

Conclusion

Containers are fundamental to organizing and managing data in Azure Blob Storage. Understanding their properties, naming conventions, and access levels is crucial for effectively utilizing this powerful cloud storage service.