Examples

Here you can find a bunch of simple examples for using ct, with some explanations about what they do. The examples here are in no way comprehensive, for a full list of all the options present in ct check out the configuration specification.

Users and groups

This is the human-readable config file. This should not be immediately passed to Container Linux. Learn more.
# This config is meant to be consumed by the config transpiler, which will
# generate the corresponding Ignition config. Do not pass this config directly
# to instances of Container Linux.

passwd:
  users:
    - name: core
      password_hash: "$6$43y3tkl..."
      ssh_authorized_keys:
        - key1
This is the raw machine configuration, which is not intended for editing. Learn more. Validate the config here.
{
  "ignition": {
    "version": "2.0.0",
    "config": {}
  },
  "storage": {},
  "systemd": {},
  "networkd": {},
  "passwd": {
    "users": [
      {
        "name": "core",
        "passwordHash": "$6$43y3tkl...",
        "sshAuthorizedKeys": [
          "key1"
        ]
      }
    ]
  }
}

This example modifies the existing core user, giving it a known password hash (this will enable login via password), and setting its ssh key.

This is the human-readable config file. This should not be immediately passed to Container Linux. Learn more.
# This config is meant to be consumed by the config transpiler, which will
# generate the corresponding Ignition config. Do not pass this config directly
# to instances of Container Linux.

passwd:
  users:
    - name: user1
      password_hash: "$6$43y3tkl..."
      ssh_authorized_keys:
        - key1
        - key2
    - name: user2
      ssh_authorized_keys:
        - key3
This is the raw machine configuration, which is not intended for editing. Learn more. Validate the config here.
{
  "ignition": {
    "version": "2.0.0",
    "config": {}
  },
  "storage": {},
  "systemd": {},
  "networkd": {},
  "passwd": {
    "users": [
      {
        "name": "user1",
        "passwordHash": "$6$43y3tkl...",
        "sshAuthorizedKeys": [
          "key1",
          "key2"
        ]
      },
      {
        "name": "user2",
        "sshAuthorizedKeys": [
          "key3"
        ]
      }
    ]
  }
}

This example will create two users, user1 and user2. The first user has a password set and two ssh public keys authorized to log in as the user. The second user doesn't have a password set (so log in via password will be disabled), but have one ssh key.

This is the human-readable config file. This should not be immediately passed to Container Linux. Learn more.
# This config is meant to be consumed by the config transpiler, which will
# generate the corresponding Ignition config. Do not pass this config directly
# to instances of Container Linux.

passwd:
  users:
    - name: user1
      password_hash: "$6$43y3tkl..."
      ssh_authorized_keys:
        - key1
      home_dir: /home/user1
      no_create_home: true
      groups:
        - wheel
        - plugdev
      shell: /bin/zsh
This is the raw machine configuration, which is not intended for editing. Learn more. Validate the config here.
{
  "ignition": {
    "version": "2.0.0",
    "config": {}
  },
  "storage": {},
  "systemd": {},
  "networkd": {},
  "passwd": {
    "users": [
      {
        "name": "user1",
        "passwordHash": "$6$43y3tkl...",
        "sshAuthorizedKeys": [
          "key1"
        ]
      }
    ]
  }
}

This example creates one user, user1, with the password hash $6$43y3tkl..., and sets up one ssh public key for the user. The user is also given the home directory /home/user1, but it's not created, the user is added to the wheel and plugdev groups, and the user's shell is set to /bin/zsh.

Storage and files

Files

This is the human-readable config file. This should not be immediately passed to Container Linux. Learn more.
# This config is meant to be consumed by the config transpiler, which will
# generate the corresponding Ignition config. Do not pass this config directly
# to instances of Container Linux.

storage:
  files:
    - path: /opt/file1
      filesystem: root
      contents:
        inline: Hello, world!
      mode: 0644
      user:
        id: 500
      group:
        id: 501
This is the raw machine configuration, which is not intended for editing. Learn more. Validate the config here.
{
  "ignition": {
    "version": "2.0.0",
    "config": {}
  },
  "storage": {
    "files": [
      {
        "filesystem": "root",
        "path": "/opt/file1",
        "contents": {
          "source": "data:,Hello%2C%20world!",
          "verification": {}
        },
        "mode": 420,
        "user": {
          "id": 500
        },
        "group": {
          "id": 501
        }
      }
    ]
  },
  "systemd": {},
  "networkd": {},
  "passwd": {}
}

This example creates a file at /opt/file with the contents Hello, world!, permissions 0644 (so readable and writable by the owner, and only readable by everyone else), and the file is owned by user uid 500 and gid 501.

This is the human-readable config file. This should not be immediately passed to Container Linux. Learn more.
# This config is meant to be consumed by the config transpiler, which will
# generate the corresponding Ignition config. Do not pass this config directly
# to instances of Container Linux.

storage:
  files:
    - path: /opt/file2
      filesystem: root
      contents:
        remote:
          url: http://example.com/file2
          compression: gzip
          verification:
            hash:
              function: sha512
              sum: 4ee6a9d20cc0e6c7ee187daffa6822bdef7f4cebe109eff44b235f97e45dc3d7a5bb932efc841192e46618f48a6f4f5bc0d15fd74b1038abf46bf4b4fd409f2e
      mode: 0644
This is the raw machine configuration, which is not intended for editing. Learn more. Validate the config here.
{
  "ignition": {
    "version": "2.0.0",
    "config": {}
  },
  "storage": {
    "files": [
      {
        "filesystem": "root",
        "path": "/opt/file2",
        "contents": {
          "compression": "gzip",
          "source": "http://example.com/file2",
          "verification": {
            "hash": "sha512-4ee6a9d20cc0e6c7ee187daffa6822bdef7f4cebe109eff44b235f97e45dc3d7a5bb932efc841192e46618f48a6f4f5bc0d15fd74b1038abf46bf4b4fd409f2e"
          }
        },
        "mode": 420,
        "user": {},
        "group": {}
      }
    ]
  },
  "systemd": {},
  "networkd": {},
  "passwd": {}
}

This example fetches a gzip-compressed file from http://example.com/file2, makes sure that it matches the provided sha512 hash, and writes it to /opt/file2.

Filesystems

This is the human-readable config file. This should not be immediately passed to Container Linux. Learn more.
# This config is meant to be consumed by the config transpiler, which will
# generate the corresponding Ignition config. Do not pass this config directly
# to instances of Container Linux.

storage:
  filesystems:
    - name: filesystem1
      mount:
        device: /dev/disk/by-partlabel/ROOT
        format: btrfs
        wipe_filesystem: true
        label: ROOT
This is the raw machine configuration, which is not intended for editing. Learn more. Validate the config here.
{
  "ignition": {
    "version": "2.0.0",
    "config": {}
  },
  "storage": {
    "filesystems": [
      {
        "name": "filesystem1",
        "mount": {
          "device": "/dev/disk/by-partlabel/ROOT",
          "format": "btrfs"
        }
      }
    ]
  },
  "systemd": {},
  "networkd": {},
  "passwd": {}
}

This example formats the root filesystem to be btrfs, and names it filesystem1 (primarily for use in the files section).

systemd units

This is the human-readable config file. This should not be immediately passed to Container Linux. Learn more.
# This config is meant to be consumed by the config transpiler, which will
# generate the corresponding Ignition config. Do not pass this config directly
# to instances of Container Linux.

systemd:
  units:
    - name: etcd-member.service
      dropins:
        - name: conf1.conf
          contents: |
            [Service]
            Environment="ETCD_NAME=infra0"
This is the raw machine configuration, which is not intended for editing. Learn more. Validate the config here.
{
  "ignition": {
    "version": "2.0.0",
    "config": {}
  },
  "storage": {},
  "systemd": {
    "units": [
      {
        "name": "etcd-member.service",
        "dropins": [
          {
            "name": "conf1.conf",
            "contents": "[Service]\nEnvironment=\"ETCD_NAME=infra0\""
          }
        ]
      }
    ]
  },
  "networkd": {},
  "passwd": {}
}

This example adds a drop-in for the etcd-member unit, setting the name for etcd to infra0 with an environment variable. More information on systemd dropins can be found in the docs.

This is the human-readable config file. This should not be immediately passed to Container Linux. Learn more.
# This config is meant to be consumed by the config transpiler, which will
# generate the corresponding Ignition config. Do not pass this config directly
# to instances of Container Linux.

systemd:
  units:
    - name: hello.service
      enabled: true
      contents: |
        [Unit]
        Description=A hello world unit!
        Type=oneshot

        [Service]
        ExecStart=/usr/bin/echo "Hello, World!"

        [Install]
        WantedBy=multi-user.target
This is the raw machine configuration, which is not intended for editing. Learn more. Validate the config here.
{
  "ignition": {
    "version": "2.0.0",
    "config": {}
  },
  "storage": {},
  "systemd": {
    "units": [
      {
        "name": "hello.service",
        "contents": "[Unit]\nDescription=A hello world unit!\nType=oneshot\n\n[Service]\nExecStart=/usr/bin/echo \"Hello, World!\"\n\n[Install]\nWantedBy=multi-user.target"
      }
    ]
  },
  "networkd": {},
  "passwd": {}
}

This example creates a new systemd unit called hello.service, enables it so it will run on boot, and defines the contents to simply echo "Hello, World!".

networkd units

This is the human-readable config file. This should not be immediately passed to Container Linux. Learn more.
# This config is meant to be consumed by the config transpiler, which will
# generate the corresponding Ignition config. Do not pass this config directly
# to instances of Container Linux.

networkd:
  units:
    - name: static.network
      contents: |
        [Match]
        Name=enp2s0

        [Network]
        Address=192.168.0.15/24
        Gateway=192.168.0.1
This is the raw machine configuration, which is not intended for editing. Learn more. Validate the config here.
{
  "ignition": {
    "version": "2.0.0",
    "config": {}
  },
  "storage": {},
  "systemd": {},
  "networkd": {
    "units": [
      {
        "name": "static.network",
        "contents": "[Match]\nName=enp2s0\n\n[Network]\nAddress=192.168.0.15/24\nGateway=192.168.0.1"
      }
    ]
  },
  "passwd": {}
}

This example creates a networkd unit to set the IP address on the enp2s0 interface to the static address 192.168.0.15/24, and sets an appropriate gateway. More information on networkd units in CoreOS can be found in the docs.

etcd

# This config is meant to be consumed by the config transpiler, which will
# generate the corresponding Ignition config. Do not pass this config directly
# to instances of Container Linux.

etcd:
  version:                     "3.0.15"
  name:                        "{HOSTNAME}"
  advertise_client_urls:       "http://{PRIVATE_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"
  initial_cluster:             "{HOSTNAME}=http://{PRIVATE_IPV4}:2380"
This is the human-readable, Container Linux Config. This should not be immediately passed to Container Linux. Learn more.

This example will create a dropin for the etcd-member systemd unit, configuring it to use the specified version and adding all the specified options. This will also enable the etcd-member unit.

This is referencing dynamic data that isn't known until an instance is booted. For more information on how this works, please take a look at the referencing dynamic data document.

Updates and Locksmithd

This is the human-readable config file. This should not be immediately passed to Container Linux. Learn more.
# This config is meant to be consumed by the config transpiler, which will
# generate the corresponding Ignition config. Do not pass this config directly
# to instances of Container Linux.

update:
  group:  "beta"
locksmith:
  reboot_strategy: "etcd-lock"
  window_start:    "Sun 1:00"
  window_length:   "2h"
This is the raw machine configuration, which is not intended for editing. Learn more. Validate the config here.
{
  "ignition": {
    "version": "2.0.0",
    "config": {}
  },
  "storage": {
    "files": [
      {
        "filesystem": "root",
        "path": "/etc/coreos/update.conf",
        "contents": {
          "source": "data:,GROUP%3Dbeta%0AREBOOT_STRATEGY%3D%22etcd-lock%22%0ALOCKSMITHD_REBOOT_WINDOW_START%3D%22Sun%201%3A00%22%0ALOCKSMITHD_REBOOT_WINDOW_LENGTH%3D%222h%22",
          "verification": {}
        },
        "mode": 420,
        "user": {},
        "group": {}
      }
    ]
  },
  "systemd": {},
  "networkd": {},
  "passwd": {}
}

This example configures the Container Linux instance to be a member of the beta group, configures locksmithd to acquire a lock in etcd before rebooting for an update, and only allows reboots during a 2 hour window starting at 1 AM on Sundays.