flatcar / coreos-cloudinit

Simple configuration tool for Flatcar Container Linux

NOTE: This project overlaps in purpose with Ignition which is where most active development is taking place. However, the Flatcar Container Linux team also continues to support and maintain this project to maintain compatibility with cloudinit based environments.

coreos-cloudinit enables a user to customize Flatcar Container Linux machines by providing either a cloud-config document or an executable script through user-data.

Configuration with cloud-config

A subset of the official cloud-config spec is implemented by coreos-cloudinit. Additionally, several Flatcar-specific options have been implemented to support interacting with unit files, bootstrapping etcd clusters, and more. All supported cloud-config parameters are documented here.

The following is an example cloud-config document:

#cloud-config

coreos:
    units:
      - name: etcd.service
        command: start

users:
  - name: core
    passwd: $1$allJZawX$00S5T756I5PGdQga5qhqv1

write_files:
  - path: /etc/resolv.conf
    content: |
        nameserver 192.0.2.2
        nameserver 192.0.2.3

Executing a Script

coreos-cloudinit supports executing user-data as a script instead of parsing it as a cloud-config document. Make sure the first line of your user-data is a shebang and coreos-cloudinit will attempt to execute it:

#!/bin/bash

echo 'Hello, world!'

user-data Field Substitution

coreos-cloudinit will replace the following set of tokens in your user-data with system-generated values.

Token	Description
$public_ipv4	Public IPv4 address of machine
$private_ipv4	Private IPv4 address of machine

These values are determined by Flatcar Container Linux based on the given provider on which your machine is running. Read more about provider-specific functionality in the Flatcar Container Linux OEM documentation.

For example, submitting the following user-data...

#cloud-config
coreos:
    etcd:
        addr: $public_ipv4:4001
        peer-addr: $private_ipv4:7001

...will result in this cloud-config document being executed:

#cloud-config
coreos:
    etcd:
        addr: 203.0.113.29:4001
        peer-addr: 192.0.2.13:7001

Bugs

Please use the Flatcar Container Linux issue tracker to report all bugs, issues, and feature requests.