EFS NFS POSIX Permissions

By default, Amazon EFS uses root squashing, a common NFS feature. This means that when the root user of an NFS client accesses the EFS file system, their UID and GID are automatically mapped to the "nobody" user and group (typically UID/GID 65534), effectively stripping the elevated privileges. This behavior can be modified with custom NFS client mount options if root access is necessary.

The root user and other user identities within Amazon EFS are defined by the UID and GID of the operating systems on the client machines that mount the EFS file system. They are not determined by AWS users or directly associated with the AWS account that creates the file system. Managing access and permissions effectively requires careful configuration of these identities on your EC2 instances or other NFS clients that access EFS.