.. _datasource_ec2:

Amazon EC2
==========

The EC2 datasource is the oldest and most widely used datasource that
cloud-init supports. This datasource interacts with a *magic* ip that is
provided to the instance by the cloud provider. Typically this ip is
``169.254.169.254`` of which at this ip a http server is provided to the
instance so that the instance can make calls to get instance userdata and
instance metadata.

Metadata is accessible via the following URL:

::

    GET http://169.254.169.254/2009-04-04/meta-data/
    ami-id
    ami-launch-index
    ami-manifest-path
    block-device-mapping/
    hostname
    instance-id
    instance-type
    local-hostname
    local-ipv4
    placement/
    public-hostname
    public-ipv4
    public-keys/
    reservation-id
    security-groups

Userdata is accessible via the following URL:

::

    GET http://169.254.169.254/2009-04-04/user-data
    1234,fred,reboot,true | 4512,jimbo, | 173,,,

Note that there are multiple versions of this data provided, cloud-init
by default uses **2009-04-04** but newer versions can be supported with
relative ease (newer versions have more data exposed, while maintaining
backward compatibility with the previous versions).
Version **2016-09-02** is required for secondary IP address support.

To see which versions are supported from your cloud provider use the following
URL:

::

    GET http://169.254.169.254/
    1.0
    2007-01-19
    2007-03-01
    2007-08-29
    2007-10-10
    2007-12-15
    2008-02-01
    2008-09-01
    2009-04-04
    ...
    latest



Configuration
-------------
The following configuration can be set for the datasource in system
configuration (in `/etc/cloud/cloud.cfg` or `/etc/cloud/cloud.cfg.d/`).

The settings that may be configured are:

 * **metadata_urls**: This list of urls will be searched for an Ec2
   metadata service. The first entry that successfully returns a 200 response
   for <url>/<version>/meta-data/instance-id will be selected.
   (default: ['http://169.254.169.254', 'http://instance-data:8773']).
 * **max_wait**:  the maximum amount of clock time in seconds that should be
   spent searching metadata_urls.  A value less than zero will result in only
   one request being made, to the first in the list. (default: 120)
 * **timeout**: the timeout value provided to urlopen for each individual http
   request.  This is used both when selecting a metadata_url and when crawling
   the metadata service. (default: 50)
 * **apply_full_imds_network_config**: Boolean (default: True) to allow
   cloud-init to configure any secondary NICs and secondary IPs described by
   the metadata service. All network interfaces are configured with DHCP (v4)
   to obtain an primary IPv4 address and route. Interfaces which have a
   non-empty 'ipv6s' list will also enable DHCPv6 to obtain a primary IPv6
   address and route. The DHCP response (v4 and v6) return an IP that matches
   the first element of local-ipv4s and ipv6s lists respectively. All
   additional values (secondary addresses) in the static ip lists will be
   added to interface.

An example configuration with the default values is provided below:

.. sourcecode:: yaml

  datasource:
    Ec2:
      metadata_urls: ["http://169.254.169.254:80", "http://instance-data:8773"]
      max_wait: 120
      timeout: 50
      apply_full_imds_network_config: true

Notes
-----
 * There are 2 types of EC2 instances network-wise: VPC ones (Virtual Private
   Cloud) and Classic ones (also known as non-VPC). One major difference
   between them is that Classic instances have their MAC address changed on
   stop/restart operations, so cloud-init will recreate the network config
   file for EC2 Classic instances every boot. On VPC instances this file is
   generated only in the first boot of the instance.
   The check for the instance type is performed by is_classic_instance()
   method.

 * For EC2 instances with multiple network interfaces (NICs) attached, dhcp4
   will be enabled to obtain the primary private IPv4 address of those NICs.
   Wherever dhcp4 or dhcp6 is enabled for a NIC, a dhcp route-metric will be
   added with the value of ``<device-number + 1> * 100`` to ensure dhcp
   routes on the primary NIC are preferred to any secondary NICs.
   For example: the primary NIC will have a DHCP route-metric of 100,
   the next NIC will be 200.

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