Running Flatcar Container Linux on AWS EC2
The current AMIs for all Flatcar Container Linux channels and EC2 regions are listed below and updated frequently. Using CloudFormation is the easiest way to launch a cluster, but it is also possible to follow the manual steps at the end of the article. Questions can be directed to the Flatcar Container Linux IRC channel or user mailing list .
At the end of the document there are instructions for deploying with Terraform.
Release retention time
After publishing, releases will remain available as public AMIs on AWS for 9 months. AMIs older than 9 months will be un-published in regular garbage collection sweeps. Please note that this will not impact existing AWS instances that use those releases. However, deploying new instances (e.g. in autoscaling groups pinned to a specific AMI) will not be possible after the AMI was un-published.
Choosing a channel
Flatcar Container Linux is designed to be updated automatically with different schedules per channel. You can disable this feature , although we don’t recommend it. Read the release notes for specific features and bug fixes.
The Alpha channel closely tracks master and is released frequently. The newest versions of system libraries and utilities will be available for testing. The current version is Flatcar Container Linux 4012.0.1.
View as json feed: amd64 arm64
The Beta channel consists of promoted Alpha releases. The current version is Flatcar Container Linux 3975.1.1.
View as json feed: amd64 arm64The Stable channel should be used by production clusters. Versions of Flatcar Container Linux are battle-tested within the Beta and Alpha channels before being promoted. The current version is Flatcar Container Linux 3815.2.5.
View as json feed: amd64 arm64Butane Configs
Flatcar Container Linux allows you to configure machine parameters, configure networking, launch systemd units on startup, and more via Butane Configs. These configs are then transpiled into Ignition configs and given to booting machines. Head over to the docs to learn about the supported features .
You can provide a raw Ignition JSON config to Flatcar Container Linux via the Amazon web console or via the EC2 API .
As an example, this Butane YAML config will start an NGINX Docker container:
variant: flatcar
version: 1.0.0
systemd:
units:
- name: nginx.service
enabled: true
contents: |
[Unit]
Description=NGINX example
After=docker.service
Requires=docker.service
[Service]
TimeoutStartSec=0
ExecStartPre=-/usr/bin/docker rm --force nginx1
ExecStart=/usr/bin/docker run --name nginx1 --pull always --log-driver=journald --net host docker.io/nginx:1
ExecStop=/usr/bin/docker stop nginx1
Restart=always
RestartSec=5s
[Install]
WantedBy=multi-user.target
Transpile it to Ignition JSON:
cat cl.yaml | docker run --rm -i quay.io/coreos/butane:latest > ignition.json
Instance storage
Ephemeral disks and additional EBS volumes attached to instances can be mounted with a .mount unit. Amazon’s block storage devices are attached differently
depending on the instance type
. Here’s the Butane Config to format and mount the first ephemeral disk, xvdb, on most instance types:
variant: flatcar
version: 1.0.0
storage:
filesystems:
- device: /dev/xvdb
format: ext4
wipe_filesystem: true
label: ephemeral
systemd:
units:
- name: media-ephemeral.mount
enabled: true
contents: |
[Mount]
What=/dev/disk/by-label/ephemeral
Where=/media/ephemeral
Type=ext4
[Install]
RequiredBy=local-fs.target
For more information about mounting storage, Amazon’s own documentation is the best source. You can also read about mounting storage on Flatcar Container Linux .
Adding more machines
To add more instances to the cluster, just launch more with the same Butane Config, the appropriate security group and the AMI for that region. New instances will join the cluster regardless of region if the security groups are configured correctly.
SSH to your instances
Flatcar Container Linux is set up to be a little more secure than other cloud images. By default, it uses the core user instead of root and doesn’t use a password for authentication. You’ll need to add an SSH key(s) via the AWS console or add keys/passwords via your Butane Config in order to log in.
To connect to an instance after it’s created, run:
ssh core@<ip address>
Multiple clusters
If you would like to create multiple clusters you will need to change the “Stack Name”. You can find the direct template file on S3 .
Manual setup
TL;DR: launch three instances of
ami-0457a742c213787a4
(amd64) in us-east-1 with a security group that has open port 22, 2379, 2380, 4001, and 7001 and the same “User Data” of each host. SSH uses the core user and you have
etcd
and
Docker
to play with.
Creating the security group
You need open port 2379, 2380, 7001 and 4001 between servers in the etcd cluster. Step by step instructions below.
Note: This step is only needed once
First we need to create a security group to allow Flatcar Container Linux instances to communicate with one another.
- Go to the security group page in the EC2 console.
- Click “Create Security Group”
- Name: flatcar-testing
- Description: Flatcar Container Linux instances
- VPC: No VPC
- Click: “Yes, Create”
- In the details of the security group, click the
Inboundtab - First, create a security group rule for SSH
- Create a new rule:
SSH - Source: 0.0.0.0/0
- Click: “Add Rule”
- Create a new rule:
- Add two security group rules for etcd communication
- Create a new rule:
Custom TCP rule - Port range: 2379
- Source: type “flatcar-testing” until your security group auto-completes. Should be something like “sg-8d4feabc”
- Click: “Add Rule”
- Repeat this process for port range 2380, 4001 and 7001 as well
- Create a new rule:
- Click “Apply Rule Changes”
Launching a test cluster
We will be launching three instances, with a few parameters in the User Data, and selecting our security group.
- Open the quick launch wizard to boot: Alpha ami-0457a742c213787a4 (amd64), Beta ami-09f2c4d0de648da87 (amd64), or Stable ami-06253dd5181f9fe62 (amd64)
- On the second page of the wizard, launch 3 servers to test our clustering
- Number of instances: 3, “Continue”
- Paste your Ignition JSON config in the EC2 dashboard into the “User Data” field, “Continue”
- Storage Configuration, “Continue”
- Tags, “Continue”
- Create Key Pair: Choose a key of your choice, it will be added in addition to the one in the gist, “Continue”
- Choose one or more of your existing Security Groups: “flatcar-testing” as above, “Continue”
- Launch!
Installation from a VMDK image
One of the possible ways of installation is to import the generated VMDK Flatcar image as a snapshot. The image file will be in https://${CHANNEL}.release.flatcar-linux.net/${ARCH}-usr/${VERSION}/flatcar_production_ami_vmdk_image.vmdk.bz2.
Make sure you download the signature (it’s available in https://${CHANNEL}.release.flatcar-linux.net/${ARCH}-usr/${VERSION}/flatcar_production_ami_vmdk_image.vmdk.bz2.sig) and check it before proceeding.
$ wget https://alpha.release.flatcar-linux.net/amd64-usr/current/flatcar_production_ami_vmdk_image.vmdk.bz2
$ wget https://alpha.release.flatcar-linux.net/amd64-usr/current/flatcar_production_ami_vmdk_image.vmdk.bz2.sig
$ gpg --verify flatcar_production_ami_vmdk_image.vmdk.bz2.sig
gpg: assuming signed data in 'flatcar_production_ami_vmdk_image.vmdk.bz2'
gpg: Signature made Thu 15 Mar 2018 10:27:57 AM CET
gpg: using RSA key A621F1DA96C93C639506832D603443A1D0FC498C
gpg: Good signature from "Flatcar Buildbot (Official Builds) <[email protected]>" [ultimate]
Then, follow the instructions in Importing a Disk as a Snapshot Using VM Import/Export . You’ll need to upload the uncompressed vmdk file to S3.
After the snapshot is imported, you can go to “Snapshots” in the EC2 dashboard, and generate an AMI image from it.
To make it work, use /dev/sda2 as the “Root device name” and you probably want to select “Hardware-assisted virtualization” as “Virtualization type”.
Using Flatcar Container Linux
Now that you have a machine booted it is time to play around. Check out the Flatcar Container Linux Quickstart guide or dig into more specific topics .
Terraform
The
aws
Terraform Provider allows to deploy machines in a declarative way.
Read more about using Terraform and Flatcar
here
.
The following Terraform v0.13 module may serve as a base for your own setup. It will also take care of registering your SSH key at AWS EC2 and managing the network environment with Terraform.
You can clone the setup from the Flatcar Terraform examples repository or create the files manually as we go through them and explain each one.
git clone https://github.com/flatcar/flatcar-terraform.git
# From here on you could directly run it, TLDR:
cd aws
export AWS_ACCESS_KEY_ID=...
export AWS_SECRET_ACCESS_KEY=...
terraform init
# Edit the server configs or just go ahead with the default example
terraform plan
terraform apply
Start with a aws-ec2-machines.tf file that contains the main declarations:
terraform {
required_version = ">= 0.13"
required_providers {
ct = {
source = "poseidon/ct"
version = "0.7.1"
}
template = {
source = "hashicorp/template"
version = "~> 2.2.0"
}
null = {
source = "hashicorp/null"
version = "~> 3.0.0"
}
aws = {
source = "hashicorp/aws"
version = "~> 3.19.0"
}
}
}
provider "aws" {
region = var.aws_region
}
resource "aws_vpc" "network" {
cidr_block = var.vpc_cidr
tags = {
Name = var.cluster_name
}
}
resource "aws_subnet" "subnet" {
vpc_id = aws_vpc.network.id
cidr_block = var.subnet_cidr
tags = {
Name = var.cluster_name
}
}
resource "aws_internet_gateway" "gateway" {
vpc_id = aws_vpc.network.id
tags = {
Name = var.cluster_name
}
}
resource "aws_route_table" "default" {
vpc_id = aws_vpc.network.id
route {
cidr_block = "0.0.0.0/0"
gateway_id = aws_internet_gateway.gateway.id
}
tags = {
Name = var.cluster_name
}
}
resource "aws_route_table_association" "public" {
route_table_id = aws_route_table.default.id
subnet_id = aws_subnet.subnet.id
}
resource "aws_security_group" "securitygroup" {
vpc_id = aws_vpc.network.id
tags = {
Name = var.cluster_name
}
}
resource "aws_security_group_rule" "outgoing_any" {
security_group_id = aws_security_group.securitygroup.id
type = "egress"
from_port = 0
to_port = 0
protocol = "-1"
cidr_blocks = ["0.0.0.0/0"]
}
resource "aws_security_group_rule" "incoming_any" {
security_group_id = aws_security_group.securitygroup.id
type = "ingress"
from_port = 0
to_port = 0
protocol = "-1"
cidr_blocks = ["0.0.0.0/0"]
}
resource "aws_key_pair" "ssh" {
key_name = var.cluster_name
public_key = var.ssh_keys.0
}
data "aws_ami" "flatcar_stable_latest" {
most_recent = true
owners = ["aws-marketplace"]
filter {
name = "architecture"
values = ["x86_64"]
}
filter {
name = "virtualization-type"
values = ["hvm"]
}
filter {
name = "name"
values = ["Flatcar-stable-*"]
}
}
resource "aws_instance" "machine" {
for_each = toset(var.machines)
instance_type = var.instance_type
user_data = data.ct_config.machine-ignitions[each.key].rendered
ami = data.aws_ami.flatcar_stable_latest.image_id
key_name = aws_key_pair.ssh.key_name
associate_public_ip_address = true
subnet_id = aws_subnet.subnet.id
vpc_security_group_ids = [aws_security_group.securitygroup.id]
tags = {
Name = "${var.cluster_name}-${each.key}"
}
}
data "ct_config" "machine-ignitions" {
for_each = toset(var.machines)
content = data.template_file.machine-configs[each.key].rendered
}
data "template_file" "machine-configs" {
for_each = toset(var.machines)
template = file("${path.module}/cl/machine-${each.key}.yaml.tmpl")
vars = {
ssh_keys = jsonencode(var.ssh_keys)
name = each.key
}
}
Create a variables.tf file that declares the variables used above:
variable "machines" {
type = list(string)
description = "Machine names, corresponding to cl/machine-NAME.yaml.tmpl files"
}
variable "cluster_name" {
type = string
description = "Cluster name used as prefix for the machine names"
}
variable "ssh_keys" {
type = list(string)
description = "SSH public keys for user 'core'"
}
variable "aws_region" {
type = string
default = "us-east-2"
description = "AWS Region to use for running the machine"
}
variable "instance_type" {
type = string
default = "t3.medium"
description = "Instance type for the machine"
}
variable "vpc_cidr" {
type = string
default = "172.16.0.0/16"
}
variable "subnet_cidr" {
type = string
default = "172.16.10.0/24"
}
An outputs.tf file shows the resulting IP addresses:
output "ip-addresses" {
value = {
for key in var.machines :
"${var.cluster_name}-${key}" => aws_instance.machine[key].public_ip
}
}
Now you can use the module by declaring the variables and a Container Linux Configuration for a machine.
First create a terraform.tfvars file with your settings:
cluster_name = "mycluster"
machines = ["mynode"]
ssh_keys = ["ssh-rsa AA... [email protected]"]
The machine name listed in the machines variable is used to retrieve the corresponding
Container Linux Config
.
For each machine in the list, you should have a machine-NAME.yaml.tmpl file with a corresponding name.
For example, create the configuration for mynode in the file machine-mynode.yaml.tmpl (The SSH key used there is not really necessary since we already set it as VM attribute):
---
passwd:
users:
- name: core
ssh_authorized_keys:
- ${ssh_keys}
storage:
files:
- path: /home/core/works
filesystem: root
mode: 0755
contents:
inline: |
#!/bin/bash
set -euo pipefail
# This script demonstrates how templating and variable substitution works when using Terraform templates for Container Linux Configs.
hostname="$(hostname)"
echo My name is ${name} and the hostname is $${hostname}
Finally, run Terraform v0.13 as follows to create the machine:
export AWS_ACCESS_KEY_ID=...
export AWS_SECRET_ACCESS_KEY=...
terraform init
terraform apply
Log in via ssh core@IPADDRESS with the printed IP address (maybe add -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null).
When you make a change to machine-mynode.yaml.tmpl and run terraform apply again, the machine will be replaced.
You can find this Terraform module in the repository for Flatcar Terraform examples .