Amazon Elastic File System
User Guide

Using File Systems

After you create a file system and mount it on your EC2 instance, there are a few things you need to know in order to use it effectively:

  • Users, groups, and related NFS-Level permissions management – When you first create the file system, there is only one root directory at /. By default, only the root user (UID 0) has read-write-execute permissions. In order for other users to modify the file system, the root user must explicitly grant them access. For more information, see Network File System (NFS)–Level Users, Groups, and Permissions.

  • Metering – Amazon EFS reports file system sizes and sizes of objects within a file system. You can view space usage in the console. For more information about how Amazon EFS reports the file system sizes, see Metering – How Amazon EFS Reports File System and Object Sizes.

  • Unsupported NFSv4 features – Amazon EFS supports NFSv4, however some of the NFSv4 features are not supported. For more information, see Unsupported NFSv4 Features.

Data Consistency in Amazon EFS

Amazon EFS provides the open-after-close consistency semantics that applications expect from NFS.

In Amazon EFS, write operations will be durably stored across Availability Zones when:

  • An application performs a synchronous write operation (for example, using the open Linux command with the O_DIRECT flag, or the fsync Linux command).

  • An application closes a file.

Amazon EFS provides stronger consistency guarantees than open-after-close semantics depending on the access pattern. Applications that perform synchronous data access and perform non-appending writes will have read-after-write consistency for data access.

Amazon EFS: How It Works

Getting Started