template version of this cloud-config: http://blog.mapstrata.com/coreos-install-to-a-vps/

cloud-config.yml

#cloud-config

hostname: HOSTNAME

write_files:
  - path: /etc/iptables.rules
    permissions: 0644
    content: |
      *filter
      :INPUT DROP [13:1170]
      :FORWARD ACCEPT [0:0]
      :OUTPUT ACCEPT [142:13212]
      -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
      -A INPUT -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j DROP
      -A INPUT -p tcp -m tcp ! --tcp-flags FIN,SYN,RST,ACK SYN -m state --state NEW -j DROP
      -A INPUT -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG FIN,SYN,RST,PSH,ACK,URG -j DROP
      -A INPUT -i lo -j ACCEPT
      -A INPUT -p icmp -j ACCEPT
      -A INPUT -p tcp -m tcp --dport SSH -j ACCEPT
      COMMIT

coreos:
  etcd:
    addr: $private_ipv4:4001
    peer-addr: $private_ipv4:7001
  units:
    - name: etcd.service
      command: start
    - name: fleet.service
      command: start
    - name: static.network
      content: |
        [Match]
        Name=DEVICE

        [Network]
        Address=ADDRESS
        Gateway=GATEWAY
        DNS=NS1
        DNS=NS2
    - name: iptables.service
      command: start
      content: |
        [Unit]
        Description=Packet Filtering Framework
        DefaultDependencies=no
        After=systemd-sysctl.service
        Before=sysinit.target

        [Service]
        Type=oneshot
        ExecStart=/usr/sbin/iptables-restore /etc/iptables.rules
        ExecReload=/usr/sbin/iptables-restore /etc/iptables.rules
        ExecStop=/usr/sbin/iptables --flush
        RemainAfterExit=yes

        [Install]
        WantedBy=multi-user.target
users:
  - name: core
    ssh-authorized-keys: 
      - PUBKEY
  - groups:
      - sudo
      - docker