Instance Metadata

What is instance-data?

Each cloud provider presents unique configuration metadata to a launched cloud instance. Cloud-init crawls this metadata and then caches and exposes this information as a standarized and versioned JSON object known as instance-data. This instance-data may then be queried or later used by cloud-init in templated configuration and scripts.

An example of a small subset of instance-data on a launched EC2 instance:

{
  "v1": {
    "cloud_name": "aws",
    "distro": "ubuntu",
    "distro_release": "jammy",
    "distro_version": "22.04",
    "instance_id": "i-06b5687b4d7b8595d",
    "machine": "x86_64",
    "platform": "ec2",
    "python_version": "3.10.4",
    "region": "us-east-2",
    "variant": "ubuntu"
  }
}

Discovery

One way to easily explore what instance-data variables are available on your machine is to use the cloud-init query tool. Warnings or exceptions will be raised on invalid instance-data keys, paths or invalid syntax.

The query command also publishes userdata and vendordata keys to the root user which will contain the decoded user and vendor data provided to this instance. Non-root users referencing userdata or vendordata keys will see only redacted values.

Note

To save time designing a user-data template for a specific cloud’s instance-data.json, use the ‘render’ cloud-init command on an instance booted on your favorite cloud. See devel for more information.

Using instance-data

Instance-data can be used in:

• User-data scripts

• Cloud-config data

• Base configuration

• Command line interface via cloud-init query or cloud-init devel render

The aforementioned configuration sources support jinja template rendering. When the first line of the provided configuration begins with ## template: jinja, cloud-init will use jinja to render that file. Any instance-data variables are surfaced as jinja template variables.

Note

Trying to reference jinja variables that don’t exist in instance-data will result in warnings in /var/log/cloud-init.log and the following string in your rendered user-data: CI_MISSING_JINJA_VAR/<your_varname>.

Sensitive data such as user passwords may be contained in instance-data. Cloud-init separates this sensitive data such that is it only readable by root. In the case that a non-root user attempts to read sensitive instance-data, they will receive redacted data or same warnings and text that occur if a variable does not exist.

Example Usage

Cloud config with instance-data

## template: jinja
#cloud-config
runcmd:
    - echo 'EC2 public hostname allocated to instance: {{
      ds.meta_data.public_hostname }}' > /tmp/instance_metadata
    - echo 'EC2 availability zone: {{ v1.availability_zone }}' >>
      /tmp/instance_metadata
    - curl -X POST -d '{"hostname": "{{ds.meta_data.public_hostname }}",
      "availability-zone": "{{ v1.availability_zone }}"}'
      https://example.com

User-data script with instance-data

## template: jinja
#!/bin/bash
{% if v1.region == 'us-east-2' -%}
echo 'Installing custom proxies for {{ v1.region }}
sudo apt-get install my-xtra-fast-stack
{%- endif %}
...

CLI discovery of instance-data

# List all instance-data keys and values as root user
% sudo cloud-init query --all
{...}

# List all top-level instance-data keys available
% cloud-init query --list-keys

# Introspect nested keys on an object
% cloud-init query -f "{{ds.keys()}}"
dict_keys(['meta_data', '_doc'])

# Failure to reference valid dot-delimited key path on a known top-level key
% cloud-init query v1.not_here
ERROR: instance-data 'v1' has no 'not_here'

# Test expected value using valid instance-data key path
% cloud-init query -f "My AMI: {{ds.meta_data.ami_id}}"
My AMI: ami-0fecc35d3c8ba8d60

# The --format command renders jinja templates, this can also be used
# to develop and test jinja template constructs
% cat > test-templating.yaml <<EOF
  {% for val in ds.meta_data.keys() %}
  - {{ val }}
  {% endfor %}
  EOF
% cloud-init query --format="$( cat test-templating.yaml )"
- instance_id
- dsmode
- local_hostname

Reference

Storage Locations

• /run/cloud-init/instance-data.json: world-readable json containing standardized keys, sensitive keys redacted

• /run/cloud-init/instance-data-sensitive.json: root-readable unredacted json blob

Format of instance-data.json

Top-level keys:

• base64_encoded_keys: A list of forward-slash delimited key paths into the instance-data.json object whose value is base64encoded for json compatibility. Values at these paths should be decoded to get the original value.

• sensitive_keys: A list of forward-slash delimited key paths into the instance-data.json object whose value is considered by the datasource as ‘security sensitive’. Only the keys listed here will be redacted from instance-data.json for non-root users.

• merged_cfg: Merged cloud-init Base Configuration from /etc/cloud/cloud.cfg and /etc/cloud/cloud-cfg.d. Values under this key could contain sensitive information such as passwords, so it is included in the sensitive-keys list which is only readable by root.

• ds: Datasource-specific metadata crawled for the specific cloud platform. It should closely represent the structure of the cloud metadata crawled. The structure of content and details provided are entirely cloud-dependent. Mileage will vary depending on what the cloud exposes. The content exposed under the ‘ds’ key is currently experimental and expected to change slightly in the upcoming cloud-init release.

• sys_info: Information about the underlying os, python, architecture and kernel. This represents the data collected by cloudinit.util.system_info.

• v1: Standardized cloud-init metadata keys, these keys are guaranteed to exist on all cloud platforms. They will also retain their current behavior and format and will be carried forward even if cloud-init introduces a new version of standardized keys with v2.

To cut down on keystrokes on the command line, cloud-init also provides top-level key aliases for any standardized v# keys present. The preceding v1 is not required of v1.var_name These aliases will represent the value of the highest versioned standard key. For example, cloud_name value will be v2.cloud_name if both v1 and v2 keys are present in instance-data.json.

cloud-init also provides jinja-safe key aliases for any instance-data keys which contain jinja operator characters such as +, -, ., /, etc. Any jinja operator will be replaced with underscores in the jinja-safe key alias. This allows for cloud-init templates to use aliased variable references which allow for jinja’s dot-notation reference such as {{ ds.v1_0.my_safe_key }} instead of {{ ds["v1.0"]["my/safe-key"] }}.

The standardized keys present:

v1._beta_keys

List of standardized keys still in ‘beta’. The format, intent or presence of these keys can change. Do not consider them production-ready.

Example output:

• [subplatform]

v1.cloud_name

Where possible this will indicate the ‘name’ of the cloud the system is running on. This is different than the ‘platform’ item. For example, the cloud name of Amazon Web Services is ‘aws’, while the platform is ‘ec2’.

If determining a specific name is not possible or provided in meta-data, then this filed may contain the same content as ‘platform’.

Example output:

• aws

• openstack

• azure

• configdrive

• nocloud

• ovf

v1.distro, v1.distro_version, v1.distro_release

This shall be the distro name, version and release as determined by cloudinit.util.get_linux_distro.

Example output:

• alpine, 3.12.0, ‘’

• centos, 7.5, core

• debian, 9, stretch

• freebsd, 12.0-release-p10,

• opensuse, 42.3, x86_64

• opensuse-tumbleweed, 20180920, x86_64

• redhat, 7.5, ‘maipo’

• sles, 12.3, x86_64

• ubuntu, 20.04, focal

v1.instance_id

Unique instance_id allocated by the cloud.

Examples output:

• i-<hash>

v1.kernel_release

This shall be the running kernel uname -r

Example output:

• 5.3.0-1010-aws

v1.local_hostname

The internal or local hostname of the system.

Examples output:

• ip-10-41-41-70

• <user-provided-hostname>

v1.machine

This shall be the running cpu machine architecture uname -m

Example output:

• x86_64

• i686

• ppc64le

• s390x

v1.platform

An attempt to identify the cloud platform instance that the system is running on.

Examples output:

• ec2

• openstack

• lxd

• gce

• nocloud

• ovf

v1.subplatform

Additional platform details describing the specific source or type of metadata used. The format of subplatform will be:

<subplatform_type> (<url_file_or_dev_path>)

Examples output:

• metadata (http://168.254.169.254)

• seed-dir (/path/to/seed-dir/)

• config-disk (/dev/cd0)

• configdrive (/dev/sr0)

v1.public_ssh_keys

A list of SSH keys provided to the instance by the datasource metadata.

Examples output:

• [‘ssh-rsa AA…’, …]

v1.python_version

The version of python that is running cloud-init as determined by cloudinit.util.system_info

Example output:

• 3.7.6

v1.region

The physical region/data center in which the instance is deployed.

Examples output:

• us-east-2

v1.availability_zone

The physical availability zone in which the instance is deployed.

Examples output:

• us-east-2b

• nova

• null

Example Output

Below is an example of /run/cloud-init/instance-data-sensitive.json on an EC2 instance:

{
 "_beta_keys": [
  "subplatform"
 ],
 "availability_zone": "us-east-1b",
 "base64_encoded_keys": [],
 "merged_cfg": {
  "_doc": "Merged cloud-init base config from /etc/cloud/cloud.cfg and /etc/cloud/cloud.cfg.d/",
  "_log": [
   "[loggers]\nkeys=root,cloudinit\n\n[handlers]\nkeys=consoleHandler,cloudLogHandler\n\n[formatters]\nkeys=simpleFormatter,arg0Formatter\n\n[logger_root]\nlevel=DEBUG\nhandlers=consoleHandler,cloudLogHandler\n\n[logger_cloudinit]\nlevel=DEBUG\nqualname=cloudinit\nhandlers=\npropagate=1\n\n[handler_consoleHandler]\nclass=StreamHandler\nlevel=WARNING\nformatter=arg0Formatter\nargs=(sys.stderr,)\n\n[formatter_arg0Formatter]\nformat=%(asctime)s - %(filename)s[%(levelname)s]: %(message)s\n\n[formatter_simpleFormatter]\nformat=[CLOUDINIT] %(filename)s[%(levelname)s]: %(message)s\n",
   "[handler_cloudLogHandler]\nclass=FileHandler\nlevel=DEBUG\nformatter=arg0Formatter\nargs=('/var/log/cloud-init.log',)\n",
   "[handler_cloudLogHandler]\nclass=handlers.SysLogHandler\nlevel=DEBUG\nformatter=simpleFormatter\nargs=(\"/dev/log\", handlers.SysLogHandler.LOG_USER)\n"
  ],
  "cloud_config_modules": [
   "snap",
   "ssh-import-id",
   "locale",
   "set-passwords",
   "grub-dpkg",
   "apt-pipelining",
   "apt-configure",
   "ubuntu-advantage",
   "ntp",
   "timezone",
   "disable-ec2-metadata",
   "runcmd",
   "byobu"
  ],
  "cloud_final_modules": [
   "package-update-upgrade-install",
   "fan",
   "landscape",
   "lxd",
   "ubuntu-drivers",
   "puppet",
   "chef",
   "mcollective",
   "salt-minion",
   "rightscale_userdata",
   "scripts-vendor",
   "scripts-per-once",
   "scripts-per-boot",
   "scripts-per-instance",
   "scripts-user",
   "ssh-authkey-fingerprints",
   "keys-to-console",
   "phone-home",
   "final-message",
   "power-state-change"
  ],
  "cloud_init_modules": [
   "migrator",
   "seed_random",
   "bootcmd",
   "write-files",
   "growpart",
   "resizefs",
   "disk_setup",
   "mounts",
   "set_hostname",
   "update_hostname",
   "update_etc_hosts",
   "ca-certs",
   "rsyslog",
   "users-groups",
   "ssh"
  ],
  "datasource_list": [
   "Ec2",
   "None"
  ],
  "def_log_file": "/var/log/cloud-init.log",
  "disable_root": true,
  "log_cfgs": [
   [
    "[loggers]\nkeys=root,cloudinit\n\n[handlers]\nkeys=consoleHandler,cloudLogHandler\n\n[formatters]\nkeys=simpleFormatter,arg0Formatter\n\n[logger_root]\nlevel=DEBUG\nhandlers=consoleHandler,cloudLogHandler\n\n[logger_cloudinit]\nlevel=DEBUG\nqualname=cloudinit\nhandlers=\npropagate=1\n\n[handler_consoleHandler]\nclass=StreamHandler\nlevel=WARNING\nformatter=arg0Formatter\nargs=(sys.stderr,)\n\n[formatter_arg0Formatter]\nformat=%(asctime)s - %(filename)s[%(levelname)s]: %(message)s\n\n[formatter_simpleFormatter]\nformat=[CLOUDINIT] %(filename)s[%(levelname)s]: %(message)s\n",
    "[handler_cloudLogHandler]\nclass=FileHandler\nlevel=DEBUG\nformatter=arg0Formatter\nargs=('/var/log/cloud-init.log',)\n"
   ]
  ],
  "output": {
   "all": "| tee -a /var/log/cloud-init-output.log"
  },
  "preserve_hostname": false,
  "syslog_fix_perms": [
   "syslog:adm",
   "root:adm",
   "root:wheel",
   "root:root"
  ],
  "users": [
   "default"
  ],
  "vendor_data": {
   "enabled": true,
   "prefix": []
  }
 },
 "cloud_name": "aws",
 "distro": "ubuntu",
 "distro_release": "focal",
 "distro_version": "20.04",
 "ds": {
  "_doc": "EXPERIMENTAL: The structure and format of content scoped under the 'ds' key may change in subsequent releases of cloud-init.",
  "_metadata_api_version": "2016-09-02",
  "dynamic": {
   "instance_identity": {
    "document": {
     "accountId": "329910648901",
     "architecture": "x86_64",
     "availabilityZone": "us-east-1b",
     "billingProducts": null,
     "devpayProductCodes": null,
     "imageId": "ami-02e8aa396f8be3b6d",
     "instanceId": "i-0929128ff2f73a2f1",
     "instanceType": "t2.micro",
     "kernelId": null,
     "marketplaceProductCodes": null,
     "pendingTime": "2020-02-27T20:46:18Z",
     "privateIp": "172.31.81.43",
     "ramdiskId": null,
     "region": "us-east-1",
     "version": "2017-09-30"
    },
    "pkcs7": [
     "MIAGCSqGSIb3DQ...",
     "REDACTED",
     "AhQUgq0iPWqPTVnT96tZE6L1XjjLHQAAAAAAAA=="
    ],
    "rsa2048": [
     "MIAGCSqGSIb...",
     "REDACTED",
     "clYQvuE45xXm7Yreg3QtQbrP//owl1eZHj6s350AAAAAAAA="
    ],
    "signature": [
     "dA+QV+LLCWCRNddnrKleYmh2GvYo+t8urDkdgmDSsPi",
     "REDACTED",
     "kDT4ygyJLFkd3b4qjAs="
    ]
   }
  },
  "meta_data": {
   "ami_id": "ami-02e8aa396f8be3b6d",
   "ami_launch_index": "0",
   "ami_manifest_path": "(unknown)",
   "block_device_mapping": {
    "ami": "/dev/sda1",
    "root": "/dev/sda1"
   },
   "hostname": "ip-172-31-81-43.ec2.internal",
   "instance_action": "none",
   "instance_id": "i-0929128ff2f73a2f1",
   "instance_type": "t2.micro",
   "local_hostname": "ip-172-31-81-43.ec2.internal",
   "local_ipv4": "172.31.81.43",
   "mac": "12:7e:c9:93:29:af",
   "metrics": {
    "vhostmd": "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"
   },
   "network": {
    "interfaces": {
     "macs": {
      "12:7e:c9:93:29:af": {
       "device_number": "0",
       "interface_id": "eni-0c07a0474339b801d",
       "ipv4_associations": {
        "3.89.187.177": "172.31.81.43"
       },
       "local_hostname": "ip-172-31-81-43.ec2.internal",
       "local_ipv4s": "172.31.81.43",
       "mac": "12:7e:c9:93:29:af",
       "owner_id": "329910648901",
       "public_hostname": "ec2-3-89-187-177.compute-1.amazonaws.com",
       "public_ipv4s": "3.89.187.177",
       "security_group_ids": "sg-0100038b68aa79986",
       "security_groups": "launch-wizard-3",
       "subnet_id": "subnet-04e2d12a",
       "subnet_ipv4_cidr_block": "172.31.80.0/20",
       "vpc_id": "vpc-210b4b5b",
       "vpc_ipv4_cidr_block": "172.31.0.0/16",
       "vpc_ipv4_cidr_blocks": "172.31.0.0/16"
      }
     }
    }
   },
   "placement": {
    "availability_zone": "us-east-1b"
   },
   "profile": "default-hvm",
   "public_hostname": "ec2-3-89-187-177.compute-1.amazonaws.com",
   "public_ipv4": "3.89.187.177",
   "reservation_id": "r-0c481643d15766a02",
   "security_groups": "launch-wizard-3",
   "services": {
    "domain": "amazonaws.com",
    "partition": "aws"
   }
  }
 },
 "instance_id": "i-0929128ff2f73a2f1",
 "kernel_release": "5.3.0-1010-aws",
 "local_hostname": "ip-172-31-81-43",
 "machine": "x86_64",
 "platform": "ec2",
 "public_ssh_keys": [],
 "python_version": "3.7.6",
 "region": "us-east-1",
 "sensitive_keys": [],
 "subplatform": "metadata (http://169.254.169.254)",
 "sys_info": {
  "dist": [
   "ubuntu",
   "20.04",
   "focal"
  ],
  "platform": "Linux-5.3.0-1010-aws-x86_64-with-Ubuntu-20.04-focal",
  "python": "3.7.6",
  "release": "5.3.0-1010-aws",
  "system": "Linux",
  "uname": [
   "Linux",
   "ip-172-31-81-43",
   "5.3.0-1010-aws",
   "#11-Ubuntu SMP Thu Jan 16 07:59:32 UTC 2020",
   "x86_64",
   "x86_64"
  ],
  "variant": "ubuntu"
 },
 "system_platform": "Linux-5.3.0-1010-aws-x86_64-with-Ubuntu-20.04-focal",
 "userdata": "#cloud-config\nssh_import_id: [<my-launchpad-id>]\n...",
 "v1": {
  "_beta_keys": [
   "subplatform"
  ],
  "availability_zone": "us-east-1b",
  "cloud_name": "aws",
  "distro": "ubuntu",
  "distro_release": "focal",
  "distro_version": "20.04",
  "instance_id": "i-0929128ff2f73a2f1",
  "kernel": "5.3.0-1010-aws",
  "local_hostname": "ip-172-31-81-43",
  "machine": "x86_64",
  "platform": "ec2",
  "public_ssh_keys": [],
  "python": "3.7.6",
  "region": "us-east-1",
  "subplatform": "metadata (http://169.254.169.254)",
  "system_platform": "Linux-5.3.0-1010-aws-x86_64-with-Ubuntu-20.04-focal",
  "variant": "ubuntu"
 },
 "variant": "ubuntu",
 "vendordata": ""
}