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devopshigh PriorityID: kubernetes-ephemeral-storage-requests

Kubernetes Container Ephemeral Storage Limits & Root Disk Eviction Safeguards

Production Kubernetes infrastructure standard. Mandates declaring ephemeral-storage requests and limits on all container specifications, preventing runaway container log writes, un-rotated temp files, or image pulls from exhausting node root filesystems and triggering node-wide pod evictions.

Prohibited Anti-Pattern: AI omits ephemeral-storage in container resources, allowing a single rogue container writing temporary files to exhaust the host node's root disk and crash the entire node.

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---
description: Kubernetes Container Ephemeral Storage Limits & Root Disk Eviction Safeguards - Production Kubernetes infrastructure standard. Mandates declaring ephemeral-storage requests and limits on all container specifications, preventing runaway container log writes, un-rotated temp files, or image pulls from exhausting node root filesystems and triggering node-wide pod evictions.
globs: **/deployment*.yaml, **/statefulset*.yaml, **/k8s/**/*.yaml
alwaysApply: false
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/kubernetes-ephemeral-storage-requests"
---

# Kubernetes Container Ephemeral Storage Limits & Root Disk Eviction Safeguards

> **Severity**: HIGH | **Category**: devops
> **Anti-Pattern Warning**: AI omits ephemeral-storage in container resources, allowing a single rogue container writing temporary files to exhaust the host node's root disk and crash the entire node.

## System Constraints
You are a Kubernetes Node Governance and Capacity Engineer. NEVER omit ephemeral-storage requests and limits in production pod specifications. If a container writes temporary files or massive diagnostic logs to root disk without limits, the Kubelet will trigger NodeHasDiskPressure and evict every pod on the machine.

## Strict Guidelines
- MUST define both requests and limits for ephemeral-storage in container resources.
- MUST set an explicit upper limit (e.g. ephemeral-storage: '2Gi') on containers performing file transformations.
- SHOULD mount emptyDir with medium: Memory for high-frequency temporary RAM scratchpads.
- MUST configure log rotation at container daemon level to avoid filling container writable layers.
- MUST alert on kubelet_volume_stats_used_bytes approaching pod limits.

## Bad vs Good Implementations
### Declaring Ephemeral Storage Limits on Kubernetes Pods

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Omitting ephemeral storage limits allows a misbehaving container to write unconstrained files to /tmp or the overlayfs, triggering a node-wide disk pressure eviction cascade.
```yaml
# FATAL: Missing ephemeral-storage allows container to fill node root disk
apiVersion: v1
kind: Pod
metadata:
  name: worker
spec:
  containers:
  - name: app
    image: worker:latest
    resources:
      limits:
        cpu: "1"
        memory: "1Gi"
        # Missing ephemeral-storage! If /tmp fills 50GB, the whole node crashes!
```

#### Production Standard (Correct)
> **Standard**: Defines an upper limit of 2Gi on ephemeral storage. If the container leaks files, the Kubelet terminates only this offending pod, shielding the host node and co-located workloads.
```yaml
apiVersion: v1
kind: Pod
metadata:
  name: worker
spec:
  containers:
  - name: app
    image: worker:latest
    resources:
      requests:
        cpu: "500m"
        memory: "512Mi"
        ephemeral-storage: "500Mi"
      limits:
        cpu: "1"
        memory: "1Gi"
        ephemeral-storage: "2Gi" # Kubelet evicts ONLY this container if it exceeds 2Gi
```
Recommended MCP Servers (mcp-serverlist.com)

Equip agent with system tools to verify code for this stack.

Kubernetes Resource & Quota Auditor MCP
Inspects pod manifests for missing ephemeral-storage, CPU, and memory limits.
Recommended Agent Skills (askills.dev)

Ready-to-use executable skill functions tailored to this stack.

askills: Kubernetes Resource Hardener
Injects ephemeral-storage requests, limits, and emptyDir memory scratchpads into manifests.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Kubernetes Container Ephemeral Storage Limits & Root Disk Eviction Safeguards

Kubernetes Container Ephemeral Storage Limits & Root Disk Eviction Safeguards defines an industrial-grade behavioral standard for devops engineering. Production Kubernetes infrastructure standard. Mandates declaring ephemeral-storage requests and limits on all container specifications, preventing runaway container log writes, un-rotated temp files, or image pulls from exhausting node root filesystems and triggering node-wide pod evictions. Modern software architectures require strict adherence to deterministic patterns to guarantee high availability, maintainability, and zero security vulnerabilities.

Framework Paradigm Shift & Drift MechanicsLLMs are trained on millions of open-source repositories containing outdated code, legacy idioms, and unpatched antipatterns. When coding assistants generate implementations for this stack, they default to common statistical tokens: AI omits ephemeral-storage in container resources, allowing a single rogue container writing temporary files to exhaust the host node's root disk and crash the entire node. Without an explicit system instruction file, developers spend hours debugging silent failures.
Failure Modes & Production Blast Radius

Hazard Analysis: What Breaks Without This Rule

The following failure modes have been cataloged from hundreds of hours of production code reviews where AI assistants produced non-compliant implementations:

Failure ModeAI Symptom (The Anti-Pattern)SeverityProduction Impact & Remedy
AI Hallucination & Deprecation DriftAI omits ephemeral-storage in container resources, allowing a single rogue container writing temporary files to exhaust the host node's root disk and crash the entire node.High
Violating this industrial standard introduces regression bugs, security risks, and unexpected runtime failures in production.
Enforce explicit behavioral system directives across all AI coding assistants in your repository.
Silent Architecture InconsistencyAI assistants produce mixed paradigms across files, creating fragmented codebase conventions.Medium
Increases cognitive load during code reviews and leads to maintenance debt across engineering teams.
Pin project conventions in .cursor/rules, CLAUDE.md, and AGENTS.md so all team agents follow identical guardrails.
Architectural Directives in Detail

Step-by-Step Production Directives

Each rule constraint below is injected into the AI agent's system prompt to establish deterministic boundaries:

1

MUST define both requests and limits for ephemeral-storage in container resources.

MUST define both requests and limits for ephemeral-storage in container resources.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
2

MUST set an explicit upper limit (e.g. ephemeral-storage

MUST set an explicit upper limit (e.g. ephemeral-storage: '2Gi') on containers performing file transformations.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
3

SHOULD mount emptyDir with medium

SHOULD mount emptyDir with medium: Memory for high-frequency temporary RAM scratchpads.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
4

MUST configure log rotation at container daemon level to avoid filling container writable layers.

MUST configure log rotation at container daemon level to avoid filling container writable layers.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
5

MUST alert on kubelet_volume_stats_used_bytes approaching pod limits.

MUST alert on kubelet_volume_stats_used_bytes approaching pod limits.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
Technical Questions & Answers

Frequently Asked Technical Questions

Common questions developers face when configuring AI coding assistants for this stack:

Q:Why is Kubernetes Container Ephemeral Storage Limits & Root Disk Eviction Safeguards critical for AI coding assistants?

Production Kubernetes infrastructure standard. Mandates declaring ephemeral-storage requests and limits on all container specifications, preventing runaway container log writes, un-rotated temp files, or image pulls from exhausting node root filesystems and triggering node-wide pod evictions. Without explicit behavioral boundaries, AI coding assistants (Cursor, Claude Code, Windsurf, Codex) rely on training data averages, which frequently produce deprecated, inefficient, or vulnerable code patterns.

Q:How does adopting this rule prevent AI hallucinations?

This rule explicitly declares what the AI must avoid (AI omits ephemeral-storage in container resources, allowing a single rogue container writing temporary files to exhaust the host node's root disk and crash the entire node.) and prescribes verified positive examples. Grounding the LLM with negative and positive pairs eliminates guesswork.

Q:Which AI coding environments are supported?

This specification is multi-platform compatible: Cursor (.cursor/rules/*.mdc & .cursorrules), Anthropic Claude Code (CLAUDE.md), Windsurf (.windsurfrules), Codex / Cline (AGENTS.md), and GitHub Copilot (.github/copilot-instructions.md).

Q:Can I combine this rule with other technology stacks?

Yes. Use the Interactive Stack Builder or download an Agent Pack to merge this rule with other frontend, backend, database, security, and DevOps rules without syntax collision.

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