Ignition is the utility used by Fedora CoreOS and RHEL CoreOS to manipulate disks during the initramfs. This includes partitioning disks, formatting partitions, writing files (regular files, systemd units, etc.), and configuring users. On first boot, Ignition reads its configuration from a source of truth (remote URL, network metadata service, hypervisor bridge, etc.) and applies the configuration.

variant: fcos
version: 1.4.0
storage:
  files:
    - path: /etc/NetworkManager/system-connections/eth0.nmconnection
      mode: 0600
      overwrite: true
      contents:
        inline: |
          [connection]
          type=ethernet
          interface-name=ens192
          [ipv4]
          method=manual
          addresses=192.168.32.11/24
          gateway=192.168.32.2
          dns=223.5.5.5;8.8.8.8
    - path: /etc/docker/daemon.json
      mode: 0600
      overwrite: true
      contents:
        inline: |
          {
              "registry-mirrors": ["https://docker.nju.edu.cn/"]
          }
passwd:
  users:
    - name: root
      password_hash: $y$j9T$kbEPbqGMlUfOaf6Ec93YZ/$YkFbCNLtyu4vMw6I2J2.jfGGN/aLtB55362.
      ssh_authorized_keys:
          - "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAACAQDRhzzs46IzGeSkZIOjYIyG7ogzwK7HnRqb9ksO95RdjbzZLs4pWM01LCMSW6sqtsMPpLTxU9zv+EkUo0YnH++NYdI0cLFBq/5DawfKw=="

./butane-x86_64-unknown-linux-gnu DockerFedora.yaml -o DockerFedora.ign