s6-overlay

**Table of Contents**

- [Quickstart](#quickstart)
- [Compatibility with v2](#compatibility-with-v2)
- [Goals](#goals)
- [Features](#features)
- [The Docker Way?](#the-docker-way)
- [Init stages](#init-stages)
- [Installation](#installation)
- [Usage](#usage)
  - [Using `CMD`](#using-cmd)
  - [Writing a service script](#writing-a-service-script)
  - [Setting the exit code of the container to the exit code of your main service](#setting-the-exit-code-of-the-container-to-the-exit-code-of-your-main-service)
  - [Fixing ownership and permissions](#fixing-ownership-and-permissions)
  - [Executing initialization and finalization tasks](#executing-initialization-and-finalization-tasks)
  - [Writing an optional finish script](#writing-an-optional-finish-script)
  - [Logging](#logging)
  - [Dropping privileges](#dropping-privileges)
  - [Read-only Root Filesystem](#read-only-root-filesystem)
  - [Container environment](#container-environment)
  - [Customizing s6-overlay's behaviour](#customizing-s6-overlay-behaviour)
  - [syslog](#syslog)
- [Performance](#performance)
- [Verifying Downloads](#verifying-downloads)
- [Notes](#notes)
- [Releases](#releases)
  - [Which architecture to use depending on your TARGETARCH](#which-architecture-to-use-depending-on-your-targetarch)
- [Contributing](#contributing)
- [Building the overlay yourself](#building-the-overlay-yourself)
- [Upgrade notes](#upgrade-notes)

# s6-overlay [![Build Status](https://api.travis-ci.org/just-containers/s6-overlay.svg?branch=master)](https://travis-ci.org/just-containers/s6-overlay)

s6-overlay is an easy-to-install (just extract a tarball or two!) set of scripts and utilities
allowing you to use existing Docker images while using [s6](https://skarnet.org/software/s6/overview.html)
as a pid 1 for your container and process supervisor for your services.

## Quickstart

Build the following Dockerfile and try it out:

```
# Use your favorite image
FROM ubuntu
ARG S6_OVERLAY_VERSION=3.2.3.2

RUN apt-get update && apt-get install -y nginx xz-utils
RUN echo "daemon off;" >> /etc/nginx/nginx.conf
CMD ["/usr/sbin/nginx"]

ADD https://github.com/just-containers/s6-overlay/releases/download/v${S6_OVERLAY_VERSION}/s6-overlay-noarch.tar.xz /tmp
RUN tar -C / -Jxpf /tmp/s6-overlay-noarch.tar.xz
ADD https://github.com/just-containers/s6-overlay/releases/download/v${S6_OVERLAY_VERSION}/s6-overlay-x86_64.tar.xz /tmp
RUN tar -C / -Jxpf /tmp/s6-overlay-x86_64.tar.xz
ENTRYPOINT ["/init"]
```

```
docker-host $ docker build -t demo .
docker-host $ docker run --name s6demo -d -p 80:80 demo
docker-host $ docker top s6demo acxf
PID                 TTY                 STAT                TIME                COMMAND
11735               ?                   Ss                  0:00                \_ s6-svscan
11772               ?                   S                   0:00                \_ s6-supervise
11773               ?                   Ss                  0:00                | \_ s6-linux-init-s
11771