boot_scrub

THE RISK

High Risk

Why boot_scrub needs a policy

This tool triggers an active operation (scrub) on the boot pool. It executes a data integrity check and repair process, which is an external system operation. While it is intended to be beneficial (repairing data), it actively runs a system process and can modify data by repairing integrity issues.

From the tool's definition Start a scrub of the boot pool to check for and repair data integrity issues

Documented attack patterns abuse exactly the kind of access boot_scrub gives an agent:

POLICY

How to control boot_scrub

PolicyLayer is an MCP gateway — it sits between your AI agents and Truenas, and nothing reaches the server without passing your rules. This is the rule we recommend for boot_scrub:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "boot_scrub": {
      "limits": [
        {
          "counter": "boot_scrub_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

boot_scrub stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

Create a free account and register Truenas — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

RATE-LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

High-risk tools in Truenas → Every high-risk tool this server exposes, in one view.
All high-risk MCP tools → Every high-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about boot_scrub

What does the boot_scrub tool do? +

Start a scrub of the boot pool to check for and repair data integrity issues. It is categorised as a Execute tool in the Truenas MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on boot_scrub? +

Register the Truenas MCP server in PolicyLayer and add a rule for boot_scrub: 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 boot_scrub? +

boot_scrub is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit boot_scrub? +

Yes. Add a rate_limit block to the boot_scrub 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 boot_scrub completely? +

Set action: deny in the PolicyLayer policy for boot_scrub. 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 boot_scrub? +

boot_scrub 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.

Enforce policy on every Truenas tool call.

Start from Truenas, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →