render-docker

A guide to running Docker containers on Render, a cloud platform for hosting applications. It explains how Render builds images from Dockerfiles or pulls ready-made images from registries.

In plain words
What is it for?
Use it to write or debug Dockerfiles, configure Render Blueprints, choose between building and pulling an image, and improve container build security or speed.
Why use it?
It helps resolve choices and configuration details that can make container deployments fail, such as build contexts, private registries, secrets, caching, and platform limits.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/render-oss/render-plugin-claude-code/render-docker
Any agent
npx skills add render-oss/render-plugin-claude-code --skill render-docker
Clone the repo
git clone --depth 1 https://github.com/render-oss/render-plugin-claude-code

Made for: Claude Code, Codex.

Per session 80 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,514 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 86% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00080 $0.01514
Opus 5 $0.00040 $0.00757
Sonnet 5 $0.00016 $0.00303
Haiku 4.5 $0.00008 $0.00151

Measured 2d ago against content hash dc892116e869, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

render-docker scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

86% identical to render-docker — 10 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/render-docker/SKILL.md · 129 lines

How it starts

The opening of the file, as written. The whole thing — 129 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Render Docker Deployments

Render uses BuildKit for Docker builds. All compute service types that support custom runtimes can use runtime: docker (build from a Dockerfile in the repo) or runtime: image (pull a prebuilt image; no Dockerfile build on Render). Deeper patterns and copy-paste templates live under references/.

When to Use

  • Authoring or debugging a Dockerfile for a Render service
  • Choosing runtime: docker vs runtime: image in a Blueprint
  • Wiring private base images or prebuilt images with registry credentials
  • Multi-stage builds, build args, secrets, and layer caching
  • Performance and security hardening of container images on Render

For full Blueprint authoring, see render-blueprints. For end-to-end deploy flows, see render-deploy.

Render Docker Builds

  • BuildKit is used for Docker builds on Render.
  • runtime: docker: Render builds an image from your repo using dockerfilePath, dockerContext, and optional dockerCommand (overrides image CMD).
  • runtime: image: Render pulls image.url; no repo-based image build. Pair with registryCredential when the registry is private.

Blueprint Configuration

Field Role
dockerfilePath Path to the Dockerfile (default ./Dockerfile)
dockerContext Build context directory (what is sent to the daemon)
dockerCommand Overrides the container CMD after the image is built
image.url Image reference for runtime: image (registry/repo:tag or digest)
registryCredential Auth for private pulls; often fromRegistryCreds → Dashboard-stored credential

Example sketch (values illustrative):

services:
  - type: web
    name: api
    runtime: docker
    region: oregon
    plan: starter
    dockerfilePath: ./Dockerfile
    dockerContext: .
    dockerCommand: node server.js
    envVars:
      - key: PORT
        value: 10000

For runtime: image, set image.url and, if needed, registryCredential per Registry Configuration below.

Read the full file on GitHub · 129 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 129 lines · 80 tokens per session scan A dc892116e869

Subscribe to this mod's changes

render-docker is a skill published in the GitHub repository render-oss/render-plugin-claude-code (0 stars, last pushed 13d ago), licensed MIT. It adds 80 tokens to every session and 1,514 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. It is 86% identical to render-docker, differing in 10 lines, and is treated as a copy.

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