Chapter 3. Red Hat support for cloud-init

By using directories and files in the following table, you can perform tasks such as:

Depending on your scenario and datasource, there can be additional files and directories important to your configuration.

You can use cloud-init with these Red Hat products:

Red Hat supports most cloud-init modules. Individual modules can contain multiple configuration options. In the following table, you can find all of the cloud-init modules that Red Hat currently supports and provides a brief description and the default module frequency. Refer to Modules in the cloud-init Documentation section for complete descriptions and options for these modules.

The following list of modules is not supported by Red Hat:

The /etc/cloud/cloud.cfg file lists the modules comprising the basic configuration for cloud-init.

The modules in the file are the default modules for cloud-init. You can configure the modules for your environment or remove modules you do not need. Modules that are included in cloud.cfg do not necessarily do anything by being listed in the file. You need to configure them individually if you want them to perform actions during one of the cloud-init phases.

The cloud.cfg file provides the chronology for running individual modules. You can add additional modules to cloud.cfg as long as Red Hat supports the modules you want to add.

The default contents of the file for Red Hat Enterprise Linux (RHEL) are as follows:

users: 1
 - default

disable_root: 1 2
ssh_pwauth:   0 3

mount_default_fields: [~, ~, 'auto', 'defaults,nofail,x-systemd.requires=cloud-init.service', '0', '2'] 4
ssh_deletekeys:   1 5
ssh_genkeytypes: ['rsa', 'ecdsa', 'ed25519'] 6
syslog_fix_perms: ~ 7
disable_vmware_customization: false 8

cloud_init_modules: 9
 - disk_setup
 - migrator
 - bootcmd
 - write-files
 - growpart
 - resizefs
 - set_hostname
 - update_hostname
 - update_etc_hosts
 - rsyslog
 - users-groups
 - ssh

cloud_config_modules: 10
 - mounts
 - locale
 - set-passwords
 - rh_subscription
 - yum-add-repo
 - package-update-upgrade-install
 - timezone
 - puppet
 - chef
 - salt-minion
 - mcollective
 - disable-ec2-metadata
 - runcmd

cloud_final_modules: 11
 - rightscale_userdata
 - scripts-per-once
 - scripts-per-boot
 - scripts-per-instance
 - scripts-user
 - ssh-authkey-fingerprints
 - keys-to-console
 - phone-home
 - final-message
 - power-state-change

system_info:
  default_user: 12
    name: cloud-user
    lock_passwd: true
    gecos: Cloud User
    groups: [adm, systemd-journal]
    sudo: ["ALL=(ALL) NOPASSWD:ALL"]
    shell: /bin/bash
  distro: rhel 13
  paths:
    cloud_dir: /var/lib/cloud 14
    templates_dir: /etc/cloud/templates 15
  ssh_svcname: sshd 16

# vim:syntax=yaml

cloud-init acts upon directives that you provide and configure. Typically, those directives are included in the cloud.cfg.d directory.

There are multiple ways to add directives. You can include directives in a file named *.cfg, which includes the heading #cloud-config. Typically, the directory would contain multiple *cfg files. There are other options for adding directives, for example, you can add a user data script. Refer to User-Data Formats for more information.

The 05_logging.cfg file sets logging information for cloud-init. The /etc/cloud/cloud.cfg.d directory includes this file, along with other cloud-init directives that you add.

cloud-init uses the logging configuration in 05_logging.cfg by default. The default contents of the file for Red Hat Enterprise Linux (RHEL) are as follows:

## This yaml formatted config file handles setting
## logger information.  The values that are necessary to be set
## are seen at the bottom.  The top '_log' are only used to remove
## redundancy in a syslog and fallback-to-file case.
##
## The 'log_cfgs' entry defines a list of logger configs
## Each entry in the list is tried, and the first one that
## works is used.  If a log_cfg list entry is an array, it will
## be joined with '\n'.
_log:
 - &log_base |
   [loggers]
   keys=root,cloudinit

   [handlers]
   keys=consoleHandler,cloudLogHandler

   [formatters]
   keys=simpleFormatter,arg0Formatter

   [logger_root]
   level=DEBUG
   handlers=consoleHandler,cloudLogHandler

   [logger_cloudinit]
   level=DEBUG
   qualname=cloudinit
   handlers=
   propagate=1

   [handler_consoleHandler]
   class=StreamHandler
   level=WARNING
   formatter=arg0Formatter
   args=(sys.stderr,)

   [formatter_arg0Formatter]
   format=%(asctime)s - %(filename)s[%(levelname)s]: %(message)s

   [formatter_simpleFormatter]
   format=[CLOUDINIT] %(filename)s[%(levelname)s]: %(message)s
 - &log_file |
   [handler_cloudLogHandler]
   class=FileHandler
   level=DEBUG
   formatter=arg0Formatter
   args=('/var/log/cloud-init.log',)
 - &log_syslog |
   [handler_cloudLogHandler]
   class=handlers.SysLogHandler
   level=DEBUG
   formatter=simpleFormatter
   args=("/dev/log", handlers.SysLogHandler.LOG_USER)

log_cfgs:
# Array entries in this list will be joined into a string
# that defines the configuration.
#
# If you want logs to go to syslog, uncomment the following line.
# - [ *log_base, *log_syslog ]
#
# The default behavior is to just log to a file.
# This mechanism that does not depend on a system service to operate.
 - [ *log_base, *log_file ]
# A file path can also be used.
# - /etc/log.conf

# This tells cloud-init to redirect its stdout and stderr to
# 'tee -a /var/log/cloud-init-output.log' so the user can see output
# there without needing to look on the console.
output: {all: '| tee -a /var/log/cloud-init-output.log'}

When cloud-init first runs, it creates a directory layout that includes information about your instance and cloud-init configuration.

The directory can include optional directories, such as /scripts/vendor.

The following is a sample directory layout for cloud-init:

/var/lib/cloud/
    - data/
       - instance-id
       - previous-instance-id
       - previous-datasource
       - previous-hostname
       - result.json
       - set-hostname
       - status.json
    - handlers/
    - instance
       - boot-finished
       - cloud-config.txt
       - datasource
       - handlers/
       - obj.pkl
       - scripts/
       - sem/
       - user-data.txt
       - user-data.txt.i
       - vendor-data.txt
       - vendor-data.txt.i
    - instances/
        f111ee00-0a4a-4eea-9c17-3fa164739c55/
          - boot-finished
          - cloud-config.txt
          - datasource
          - handlers/
          - obj.pkl
          - scripts/
          - sem/
          - user-data.txt
          - user-data.txt.i
          - vendor-data.txt
          - vendor-data.txt.i
    - scripts/
       - per-boot/
       - per-instance/
       - per-once/
       - vendor/
    - seed/
    - sem/
       - config_scripts_per_once.once