Base configuration


This documentation is intended for custom image creators, such as distros and cloud providers, not end users. Modifying the base configuration should not be necessary for end users and can result in a system that may be unreachable or may no longer boot.

Cloud-init base config is primarily defined in two places:

  • /etc/cloud/cloud.cfg

  • /etc/cloud/cloud.cfg.d/*.cfg

See the configuration sources explanation for more information on how these files get sourced and combined with other configuration.


cloud.cfg isn’t present in any of cloud-init’s source files. The configuration is templated and customised for each distribution supported by cloud-init.

Base configuration keys

Module keys

Modules are grouped into the following keys:

  • cloud_init_modules: Modules run during network timeframe.

  • cloud_config_modules: Modules run during config timeframe.

  • cloud_final_modules: Modules run during final timeframe.

Each module definition contains an array of strings, where each string is the name of the module. Each name is taken directly from the module filename, with the cc_ prefix and .py suffix removed, and with - and _ being interchangeable.

Alternatively, in place of the module name, an array of <name>, <frequency>[, <args>] args may be specified. See the module creation guidelines for more information on frequency and args.


Most modules won’t run at all if they’re not triggered via a respective user data key, so removing modules or changing the run frequency is not a recommended way to reduce instance boot time.


To specify that only run during final timeframe:

- final_message

To change the frequency from the default of ALWAYS to ONCE:

- [final_message, once]

To include default arguments to the module (that may be overridden by user data):

- [final_message, once, "my final message"]

Datasource keys

Many datasources allow configuration of the datasource for use in querying the datasource for metadata using the datasource key. This configuration is datasource dependent and can be found under each datasource’s respective documentation. It will generally take the form of:


System info keys

These keys are used for setup of cloud-init itself, or the datasource or distro. Anything under system_info cannot be overridden by vendor data, user data, or any other handlers or transforms. In some cases there may be a system_info key used for the distro, while the same key is used outside of system_info for a user data module. Both keys will be processed independently.

  • system_info: Top-level key.

    • paths: Definitions of common paths used by cloud-init.

      • cloud_dir: Default: /var/lib/cloud.

      • templates_dir: Default: /etc/cloud/templates.

    • distro: Name of distro being used.

    • default_user: Defines the default user for the system using the same user configuration as Users and Groups. Note that this CAN be overridden if a users configuration is specified without a - default entry.

    • ntp_client: The default NTP client for the distro. Takes the same form as ntp_client defined in NTP.

    • package_mirrors: Defines the package mirror info for apt.

    • ssh_svcname: The SSH service name. For most distros this will be either ssh or sshd.

    • network: Top-level key for distro-specific networking configuration.

      • renderers: Prioritised list of networking configurations to try on this system. The first valid entry found will be used. Options are:

        • eni: For /etc/network/interfaces.

        • network-manager

        • netplan

        • networkd: For systemd-networkd.

        • freebsd

        • netbsd

        • openbsd

      • activators: Prioritised list of networking tools to try to activate network on this system. The first valid entry found will be used. Options are:

        • eni: For ifup/ifdown.

        • netplan: For netplan generate/netplan apply.

        • network-manager: For nmcli connection load/ nmcli connection up.

        • networkd: For ip link set up/ip link set down.

    • apt_get_command: Command used to interact with APT repositories. Default: apt-get.

    • apt_get_upgrade_subcommand: APT subcommand used to upgrade system. Default: dist-upgrade.

    • apt_get_wrapper: Command used to wrap the apt-get command.

      • enabled: Whether to use the specified apt_wrapper command. If set to auto, use the command if it exists on the PATH. Default: true.

      • command: Command used to wrap any apt-get calls. Default: eatmydata.

Logging keys

See the logging explanation for a comprehensive logging explanation. Note that cloud-init has a default logging definition that shouldn’t need to be altered. It is defined in this instance at /etc/cloud/cloud.cfg.d/05_logging.cfg.

The logging keys used in the base configuration are as follows:


A standard python fileConfig formatted log configuration. This is the primary logging configuration key and will take precedence over log_cfgs or log_basic keys.


A list of logging configs in fileConfig format to apply when running cloud-init. Note that log_cfgs is used in /etc/cloud.cfg.d/05_logging.cfg.


Boolean value to determine if cloud-init should apply a basic default logging configuration if none has been provided. Defaults to true but only takes effect if logcfg or log_cfgs hasn’t been defined.


If and how to redirect stdout/stderr. Defined in /etc/cloud.cfg.d/05_logging.cfg and explained in the logging explanation.


Takes a list of <owner:group> strings and will set the owner of def_log_file accordingly.


Only used in conjunction with syslog_fix_perms. Specifies the filename to be used for setting permissions. Defaults to /var/log/cloud-init.log.

Other keys


The network configuration to be applied to this instance.


Prioritised list of python packages to search when finding a datasource. Automatically includes cloudinit.sources.


This key contains a prioritised list of datasources that cloud-init attempts to discover on boot. By default, this is defined in /etc/cloud/cloud.cfg.d.

There are a few reasons to modify the datasource_list:

  1. Override default datasource discovery priority order

  2. Force cloud-init to use a specific datasource: A single entry in the list (or a single entry and None) will override datasource discovery, which will force the specified datasource to run.

  3. Remove known invalid datasources: this might improve boot speed on distros that do not use ds-identify to detect and select the datasource,


This key is unique in that it uses a subset of YAML syntax. It requires that the key and its contents, a list, must share a single line - no newlines.


Allows the user to disable vendor_data or vendor_data2 along with providing a prefix for any executed scripts.

Format is a dict with enabled and prefix keys:

  • enabled: A boolean indicating whether to enable or disable the vendor_data.

  • prefix: A path to prepend to any vendor_data-provided script.


By default, cloud-init searches for a datasource on every boot. Setting this to true will disable this behaviour. This is useful if your datasource information will not be present every boot. Default: false.


On an Ubuntu system, /etc/cloud/cloud.cfg should look similar to:

# The top level settings are used as module and base configuration.
# A set of users which may be applied and/or used by various modules
# when a 'default' entry is found it will reference the 'default_user'
# from the distro configuration specified below
- default

# If this is set, 'root' will not be able to ssh in and they
# will get a message to login instead as the default $user
disable_root: true

# This will cause the set+update hostname module to not operate (if true)
preserve_hostname: false

# If you use datasource_list array, keep array items in a single line.
# If you use multi line array, ds-identify script won't read array items.
# Example datasource config
# datasource:
#    Ec2:
#      metadata_urls: [ '' ]
#      timeout: 5 # (defaults to 50 seconds)
#      max_wait: 10 # (defaults to 120 seconds)

# The modules that run in the 'init' stage
- seed_random
- bootcmd
- write_files
- growpart
- resizefs
- disk_setup
- mounts
- set_hostname
- update_hostname
- update_etc_hosts
- ca_certs
- rsyslog
- users_groups
- ssh

# The modules that run in the 'config' stage
- wireguard
- snap
- ubuntu_autoinstall
- ssh_import_id
- keyboard
- locale
- set_passwords
- grub_dpkg
- apt_pipelining
- apt_configure
- ubuntu_pro
- ntp
- timezone
- disable_ec2_metadata
- runcmd
- byobu

# The modules that run in the 'final' stage
- package_update_upgrade_install
- fan
- landscape
- lxd
- ubuntu_drivers
- write_files_deferred
- puppet
- chef
- ansible
- mcollective
- salt_minion
- reset_rmc
- scripts_vendor
- scripts_per_once
- scripts_per_boot
- scripts_per_instance
- scripts_user
- ssh_authkey_fingerprints
- keys_to_console
- install_hotplug
- phone_home
- final_message
- power_state_change

# System and/or distro specific settings
# (not accessible to handlers/transforms)
  # This will affect which distro class gets used
  distro: ubuntu
  # Default user name + that default users groups (if added/used)
    name: ubuntu
      - permit nopass ubuntu
    lock_passwd: True
    gecos: Ubuntu
    groups: [adm, cdrom, dip, lxd, sudo]
    sudo: ["ALL=(ALL) NOPASSWD:ALL"]
    shell: /bin/bash
    dhcp_client_priority: [dhclient, dhcpcd, udhcpc]
    renderers: ['netplan', 'eni', 'sysconfig']
    activators: ['netplan', 'eni', 'network-manager', 'networkd']
  # Automatically discover the best ntp_client
  ntp_client: auto
  # Other config here will be given to the distro class and/or path classes
    cloud_dir: /var/lib/cloud/
    templates_dir: /etc/cloud/templates/
    - arches: [i386, amd64]
        - http://%(ec2_region)
        - http://%(availability_zone)
        - http://%(region)
        security: []
    - arches: [arm64, armel, armhf]
        - http://%(ec2_region)
        - http://%(availability_zone)
        - http://%(region)
        security: []
    - arches: [default]
  ssh_svcname: ssh

# configure where output will go
  init: "> /var/log/my-cloud-init.log"
  config: [ ">> /tmp/foo.out", "> /tmp/foo.err" ]
    output: "| tee /tmp/final.stdout | tee /tmp/bar.stdout"
    error: "&1"

# Set `true` to enable the stop searching for a datasource on boot.
manual_cache_clean: False

# def_log_file and syslog_fix_perms work together
# if
# - logging is set to go to a log file 'L' both with and without syslog
# - and 'L' does not exist
# - and syslog is configured to write to 'L'
# then 'L' will be initially created with root:root ownership (during
# cloud-init), and then at cloud-config time (when syslog is available)
# the syslog daemon will be unable to write to the file.
# to remedy this situation, 'def_log_file' can be set to a filename
# and syslog_fix_perms to a string containing "<user>:<group>"
def_log_file: /var/log/my-logging-file.log
syslog_fix_perms: syslog:root