filesystem_set_permissions

Set UNIX permissions on a file or directory. Can optionally apply recursively and strip existing ACLs.

SERVERTruenas SOURCEspranab/truenas-mcp

Medium RISK CLASS

Category Write

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/spranab-truenas-mcp/filesystem-set-permissions.md

WHAT IT DOES

What filesystem_set_permissions does on Truenas

AI agents use filesystem_set_permissions to create or update resources in Truenas, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Truenas environment.

RISK

Why filesystem_set_permissions is rated Medium

This tool modifies file and directory permissions, which are write operations that change system state. While permission changes are technically reversible (can be undone by resetting to previous values), the impact is significant—incorrect permission assignments could lock out legitimate users or expose sensitive data.

From the tool's definition Tool description states it 'Set[s] UNIX permissions on a file or directory' and can 'apply recursively and strip existing ACLs'. This modifies filesystem metadata and access control configurations, which are reversible but impactful changes.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs filesystem_set_permissions safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Truenas, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For filesystem_set_permissions, this is the rule to start with:

filesystem_set_permissions Rate-limited

filesystem_set_permissions stays usable, but capped: an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "filesystem_set_permissions": {
      "limits": [
        {
          "counter": "filesystem_set_permissions_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Truenas, apply this rule, and every filesystem_set_permissions call is checked against it from then on.

FAQ

Questions about filesystem_set_permissions

What does the filesystem_set_permissions tool do? +

Set UNIX permissions on a file or directory. Can optionally apply recursively and strip existing ACLs. It is categorised as a Write tool in the Truenas MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on filesystem_set_permissions? +

Register the Truenas MCP server in PolicyLayer and add a rule for filesystem_set_permissions: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Truenas. Nothing to install.

What risk level is filesystem_set_permissions? +

filesystem_set_permissions is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit filesystem_set_permissions? +

Yes. Add a rate_limit block to the filesystem_set_permissions rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block filesystem_set_permissions completely? +

Set action: deny in the PolicyLayer policy for filesystem_set_permissions. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides filesystem_set_permissions? +

filesystem_set_permissions is provided by the Truenas MCP server (spranab/truenas-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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