The Concept of Root Squash: In the world of NFS, " Root Squashing " is a fundamental security feature. By default, most modern storage systems (including FlashArray File Services) do not trust the " root " user of a remote client. This prevents a user with administrative access on a random laptop or server from gaining full administrative control over the files on the central storage.

Mounting vs. Accessing:

Mounting: This is the process of attaching the remote export to the local file system. If the Export Policy allows the client IP to connect, the mount will succeed.

Accessing: Once mounted, the array evaluates the identity of the user. If Root Squash is enabled, the array " squashes " the root user (UID 0) and maps it to a non-privileged user (usually nobody or anonymous ). Consequently, the client ' s root user loses their administrative permissions when trying to read/write files.

The Export Policy Setting: The behavior described (able to mount but permission denied for files as root) is almost always caused by the User ID Mapping or Access rules within the Export Policy .

To resolve this, an administrator must edit the specific rule in the Export Policy and enable " No Root Squash " (or change the mapping to allow root access). This tells the FlashArray to honor the client ' s root identity.

Why Options A and B are incorrect:

Managed Directory: This is where you set the directory structure and quotas, but it doesn ' t control the protocol-level identity mapping.

File System: While a file system has underlying permissions, if the mount is successful but specifically blocks the root user, the " gatekeeper " is the Export Policy rule.