CoreOS introduction - by johann romefort
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CoreOS is a minimal Linux distribution focused on security and running containers. It uses automatic updates and etcd for service discovery to ensure services are always running across a cluster. Fleet is CoreOS' init system that uses etcd to schedule and run containers across nodes, providing high availability. The document provides steps for creating a CoreOS cluster on Digital Ocean including generating a discovery URL, writing a cloud config, creating a service unit file, and using fleet to schedule and manage the service.
CoreOS introduction - by johann romefort
- 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
- 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
- 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…