Amazon EC2 instances can access instance-specific metadata as well as data supplied when launching the instances. This data can be used to build more generic AMIs that can be modified by configuration files supplied at launch time.
If you run web servers for various small businesses, they can all use the same AMI and retrieve their content from the Amazon S3 bucket you specify at launch.
To add a new customer at any time, simply create a bucket for the customer, add their content, and launch your AMI.
The data available to instances is categorized into metadata and user-supplied data.
Metadata is specific to an instance and is described in the following table.
| Data | Description | Version Introduced |
|---|---|---|
| ami-id | The AMI ID used to launch the instance. | 1.0 |
| ami-launch-index | The index of this instance in the reservation (per AMI). | 1.0 |
| ami-manifest-path | The manifest path of the AMI with which the instance was launched. | 1.0 |
| ancestor-ami-ids | The AMI IDs of any instances that were rebundled to create this AMI. | 2007-10-10 |
| block-device-mapping | Defines native device names to use when exposing virtual devices. | 2007-10-10 |
| instance-id | The ID of this instance. | 1.0 |
| instance-type | The type of instance to launch. For more information, see Instance Types. | 2007-08-29 |
| local-hostname | The local hostname of the instance. | 2007-01-19 |
| local-ipv4 | Public IP address if launched with direct addressing; private IP address if launched with public addressing. | 1.0 |
| kernel-id | The ID of the kernel launched with this instance, if applicable. | 2008-02-01 |
| placement/availability-zone | The availability zone in which the instance launched. | 2008-02-01 |
| product-codes | Product codes associated with this instance. | 2007-03-01 |
| public-hostname | The public hostname of the instance. | 2007-01-19 |
| public-ipv4 | The public IP address | 2007-01-19 |
| public-keys/ | Public keys. Only available if supplied at instance launch time | 1.0 |
| ramdisk-id | The ID of the RAM disk launched with this instance, if applicable. | 2008-02-01 |
| reservation-id | ID of the reservation. | 1.0 |
| security-groups | Names of the security groups the instance is launched in. Only available if supplied at instance launch time | 1.0 |
User-supplied data is treated as opaque data: what you give us is what you get back.
![[Note]](note.png)
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Note |
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An instance retrieves the data by querying a web server using a
Query API. The base URI of all requests is
http://169.254.169.254/2008-08-08/ where
2008-08-08 indicates the API version.
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Note |
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Amazon EC2 Version 1.0 is part of a legacy versioning scheme. Newer versions follow a date based versioning scheme. For more information on the versioning scheme used by Amazon EC2, see API Versioning. |
The latest version of the API is always available using the
URI http://169.254.169.254/latest.
Although only your specific instance can access launch data, the data is not protected by cryptographic methods. You should take suitable precautions to protect sensitive data (such as long lived encryption keys).
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Note |
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You are not billed for HTTP requests used to retrieve metadata and user-supplied data. |