CoreOS is a minimal Linux distribution focused on security and running containers. It uses automatic updates and etcd for service discovery to ensure containers are always running across a cluster. Fleet is CoreOS' init system that uses etcd to schedule and run containers across nodes, providing high availability. To set up a CoreOS cluster on Digital Ocean, you generate a discovery URL, write a cloud config, create service unit files, and use fleetctl to submit, list, and monitor services.

1. CoreOS Introduction
Johann Romefort
http://containera.io

2. What is CoreOS?

3. What is CoreOS?
• A minimal Linux distro (~100MB)
• Huge focus on security: CoreOS
mission is “Secure the Internet”
• The best way to run containers
• A read-only rootfs
• Automatic updates

4. Automatic Updates
• Active / Passive partitions
• Update Partition B while partition A is
running. Reboot to partition B, reverse
to A if any problem found.
• Reboot causes app downtime…
unless…

5. etcd
• Distributed Key-Value store
• Service discovery
• No local configuration

6. Running Containers on
CoreOS

7. Fleet
• Distributed init system for cluster
• Uses etcd
• Actually relies on systemd: Submit a
systemd Unit file and handles scheduling
on the cluster
• Enable high-availability services

8. Running Containers on
fleet

9. Boot Sequence
• Look for cloud-config
• Lookup how to join an existing cluster
• Start etcd service
• Start fleet service

10. Creating a CoreOS
cluster on
Digital Ocean

11. Pre-requesites
• Make sure you use a SSH key
• Create a DigitalOcean Personal
Access Token (to use the DO API)

12. Generate a New
Discovery URL
• Unique address that stores peer
CoreOS addresses and metadata

13. Write a Cloud-Config
metadata: region=europe,public_ip=$public_ipv4

14. Create a Service Unit file
• hello.service

15. Using fleet to schedule
a service
• fleetctl submit hello.service
• fleetctl list-unit-files
• fleetctl cat hello.service
• fleetctl start hello.service
• fleetctl list-units
• fleetctl status hello.service
• fleetctl journal hello.service

16. What’s next…

17. Thank You!
romefort@gmail.com
http://linkedin.com/in/romefort
http://twitter.com/romefort
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