CoreOS intro
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CoreOS is a minimal OS designed to host containers. It uses automatic updates and cluster management via tools like Fleet and etcd. CoreOS clusters are configured in etcd, a highly available key-value store. Services are defined and launched across the cluster using Fleet and systemd unit files. Cloud config handles early initialization and configuration of instances.
![Unit file
[Unit]
Description=A Redis Server
[Service]
TimeoutStartSec=0
EnvironmentFile=/etc/environment
Environment="IMAGE=teemow/redis"
ExecStartPre=/usr/bin/docker pull $IMAGE
ExecStart=/bin/bash -c "exec /usr/bin/docker run --rm -p
$COREOS_PRIVATE_IPV4::6379 --name %n $IMAGE"
ExecStop=-/usr/bin/docker kill %n](https://image.slidesharecdn.com/coreosintro-140526033631-phpapp01/85/CoreOS-intro-9-320.jpg)
CoreOS intro
- 2. CoreOS ● Minimal OS to host your containers ● Automatic Updates ● Cluster Management ● Service Discovery
- 4. CoreOS 101 ● minimal Gentoo ● PXE, KVM, AWS, OpenStack, Vagrant ● read-only rootfs (writable overlay) ● cloud config ● etcd ● systemd / fleet ● locksmith
- 5. Cloud Config ● handles early initialization of a cloud instance ● configure fleet, etcd ● create users ● write files ● etc...
- 6. Etcd ● Highly available K/V store ● Basis for ○ Configuration management ○ Service Discovery ● Raft consensus algorithm ● Discovery API ● REST Interface
- 7. Locksmith ● reboot strategies for CoreOS updates ● uses etcd for distributed locks
- 8. Fleet ● Define and launch containers ● Fleet is systemd for the cluster ● Utilizes etcd + systemd
- 9. Unit file [Unit] Description=A Redis Server [Service] TimeoutStartSec=0 EnvironmentFile=/etc/environment Environment="IMAGE=teemow/redis" ExecStartPre=/usr/bin/docker pull $IMAGE ExecStart=/bin/bash -c "exec /usr/bin/docker run --rm -p $COREOS_PRIVATE_IPV4::6379 --name %n $IMAGE" ExecStop=-/usr/bin/docker kill %n
- 10. Launch a service # start fleetctl --tunnel my.coreos-cluster.com start redis.service # status fleetctl --tunnel my.coreos-cluster.com list-units fleetctl --tunnel my.coreos-cluster.com status redis.service fleetctl --tunnel my.coreos-cluster.com journal redis.service # stop fleetctl --tunnel my.coreos-cluster.com stop redis.service fleetctl --tunnel my.coreos-cluster.com destroy redis.service
- 11. CoreOS ● distributed containers ● configuration in etcd
- 12. Sidekick ● Keep configuration out of your app
- 13. Ambassador ● Reverse proxy for your service ● Keep service discovery out of your app
- 14. CoreOS ● Great foundation to create flexible distributed infrastructures ● Unix philosophy
- 15. Lessons Learned ● 150+ Instances on AWS ● Micro Services ● Polyglot Persistence ● DevOps