Fedora CoreOSのインストールで使用している構成ファイルconfig.yamlのサンプルになります。
variant: fcos
version: 1.0.0
passwd:
  users:
  - name:          core
    password_hash: "{PASSWORD}"
    ssh_authorized_keys:
    - "ssh-ed25519 {SSHKEY} Windows PC"
storage:
  files:
  - path:       /etc/NetworkManager/system-connections/eth1.nmconnection
    mode:       0600
    contents:
      inline:   |
        [connection]
        type=ethernet
        interface-name=eth1
        [ipv4]
        method=manual
        addresses=192.168.100.2/24
  - path:       /etc/hostname
    overwrite:  true
    mode:       0644
    contents:
      inline:   "coreos"
  - path:       /etc/hosts
    append:
    - inline:   |
        192.168.100.2   coreos.localnet
        192.168.100.1   glusterfs.localnet
        192.168.100.1   mariadb.localnet
        192.168.100.1   postgresql.localnet
  - path:       /etc/ssh/sshd_config
    append:
    - inline:   |
        #
        LoginGraceTime         20
        PermitRootLogin        no
        AllowUsers             core
        GSSAPIAuthentication   no
        MaxAuthTries           1
        ClientAliveInterval    60