Using Flannel as a soft-defined networking solution for rkt containers

Flannel is an open source soft-defined networking solution for containers. It works by making a subnets available to hosts for use with container runtimes.

It is one of the many new featured introduced in rkt 0.8, which was released in August.

In the following blog post, you’ll read how to use Flannel as a soft-defined networking solution for rkt containers running on CoreOS Linux.

It begins like this:

Let’s walk through setting up rkt with flannel on CoreOS. We start with the CoreOS image 808.0 or later and bring up 3 instances clustered together using the following cloud-config:

#cloud-config

coreos:
  units:
    - name: etcd2.service
      command: start

    - name: flanneld.service
      drop-ins:
        - name: 50-network-config.conf
          content: |
            [Service]
            ExecStartPre=/usr/bin/etcdctl set /coreos.com/network/config '{ "network": "10.1.0.0/16" }'

      command: start

  etcd2:
    discovery: $YOUR_DISCOVERY_TOKEN
    advertise-client-urls: http://$public_ipv4:2379
    initial-advertise-peer-urls: http://$private_ipv4:2380
    listen-client-urls: http://0.0.0.0:2379
    listen-peer-urls: http://$private_ipv4:2380

write_files:
  - path: "/etc/rkt/net.d/10-containernet.conf"
    permissions: "0644"
    owner: "root"
    content: |
      {
        "name": "containernet",
        "type": "flannel"
      }