packer-cn/website/source/intro/getting-started/build-image.html.markdown

---
layout: "intro"
page_title: "Build an Image"
prev_url: "/intro/getting-started/setup.html"
next_url: "/intro/getting-started/provision.html"
next_title: "Provision"
---

# Build an Image

With Packer installed, let's just dive right into it and build our first
image. Our first image will be an [Amazon EC2 AMI](http://aws.amazon.com/ec2/)
with Redis pre-installed. This is just an example. Packer can create images
for [many platforms](/intro/platforms.html) with anything pre-installed.

If you don't have an AWS account, [create one now](http://aws.amazon.com/free/).
For the example, we'll use a "t1.micro" instance to build our image, which
qualifies under the AWS [free-tier](http://aws.amazon.com/free/), meaning
it will be free. If you already have an AWS account, you may be charged some
amount of money, but it shouldn't be more than a few cents.

<div class="alert alert-block alert-warn">
<strong>Note</strong> that if you're not using an account that qualifies under
the AWS <a href="http://aws.amazon.com/free/">free-tier</a>, you may be
charged to run these examples. The charge should only be a few cents, but
we're not responsible if it ends up being more.
</div>

Packer can build images for [many platforms](/intro/platforms.html) other than
AWS, but AWS requires no additional software installed on your computer and
their [free-tier](http://aws.amazon.com/free/) makes it free to use for most
people. This is why we chose to use AWS for the example. If you're uncomfortable
setting up an AWS account, feel free to follow along as the basic principles
apply to the other platforms as well.

## The Template

The configuration file used to define what image we want built and how
is called a _template_ in Packer terminology. The format of a template
is simple [JSON](http://www.json.org/). JSON struck the best balance between
human-editable and machine-editable, allowing both hand-made templates as well
as machine generated templates to easily be made.

We'll start by creating the entire template, then we'll go over each section
briefly. Create a file `example.json` and fill it with the following contents:

<pre class="prettyprint">
{
  "variables": {
    "aws_access_key": "",
    "aws_secret_key": ""
  },
  "builders": [{
    "type": "amazon-ebs",
    "access_key": "{{user `aws_access_key`}}",
    "secret_key": "{{user `aws_secret_key`}}",
    "region": "us-east-1",
    "source_ami": "ami-de0d9eb7",
    "instance_type": "t1.micro",
    "ssh_username": "ubuntu",
    "ami_name": "packer-example {{timestamp}}"
  }]
}
</pre>

When building, you'll pass in the `aws_access_key` and `aws_secret_key` as
a [user variable](/docs/templates/user-variables.html), keeping your secret
keys out of the template. You can create security credentials
on [this page](https://console.aws.amazon.com/iam/home?#security_credential).
An example IAM policy document can be found in the [Amazon EC2 builder docs](/docs/builders/amazon.html).

This is a basic template that is ready-to-go. It should be immediately recognizable
as a normal, basic JSON object. Within the object, the `builders` section
contains an array of JSON objects configuring a specific _builder_. A
builder is a component of Packer that is responsible for creating a machine
and turning that machine into an image.

In this case, we're only configuring a single builder of type `amazon-ebs`.
This is the Amazon EC2 AMI builder that ships with Packer. This builder
builds an EBS-backed AMI by launching a source AMI, provisioning on top of
that, and re-packaging it into a new AMI.

The additional keys within the object are configuration for this builder, specifying things
such as access keys, the source AMI to build from, and more.
The exact set of configuration variables available for a builder are
specific to each builder and can be found within the [documentation](/docs).

Before we take this template and build an image from it, let's validate the template
by running `packer validate example.json`. This command checks the syntax
as well as the configuration values to verify they look valid. The output should
look similar to below, because the template should be valid. If there are
any errors, this command will tell you.

```
$ packer validate example.json
Template validated successfully.
```

Next, let's build the image from this template.

An astute reader may notice that we said earlier we'd be building an
image with Redis pre-installed, and yet the template we made doesn't reference
Redis anywhere. In fact, this part of the documentation will only cover making
a first basic, non-provisioned image. The next section on provisioning will
cover installing Redis.

## Your First Image

With a properly validated template. It is time to build your first image.
This is done by calling `packer build` with the template file. The output
should look similar to below. Note that this process typically takes a
few minutes.

```
$ packer build \
    -var 'aws_access_key=YOUR ACCESS KEY' \
    -var 'aws_secret_key=YOUR SECRET KEY' \
    example.json
==> amazon-ebs: amazon-ebs output will be in this color.

==> amazon-ebs: Creating temporary keypair for this instance...
==> amazon-ebs: Creating temporary security group for this instance...
==> amazon-ebs: Authorizing SSH access on the temporary security group...
==> amazon-ebs: Launching a source AWS instance...
==> amazon-ebs: Waiting for instance to become ready...
==> amazon-ebs: Connecting to the instance via SSH...
==> amazon-ebs: Stopping the source instance...
==> amazon-ebs: Waiting for the instance to stop...
==> amazon-ebs: Creating the AMI: packer-example 1371856345
==> amazon-ebs: AMI: ami-19601070
==> amazon-ebs: Waiting for AMI to become ready...
==> amazon-ebs: Terminating the source AWS instance...
==> amazon-ebs: Deleting temporary security group...
==> amazon-ebs: Deleting temporary keypair...
==> amazon-ebs: Build finished.

==> Builds finished. The artifacts of successful builds are:
--> amazon-ebs: AMIs were created:

us-east-1: ami-19601070
```

At the end of running `packer build`, Packer outputs the _artifacts_
that were created as part of the build. Artifacts are the results of a
build, and typically represent an ID (such as in the case of an AMI) or
a set of files (such as for a VMware virtual machine). In this example,
we only have a single artifact: the AMI in us-east-1 that was created.

This AMI is ready to use. If you wanted you can go and launch this AMI
right now and it would work great.

<div class="alert alert-block alert-info">
<strong>Note:</strong> Your AMI ID will surely be different than the
one above. If you try to launch the one in the example output above, you
will get an error. If you want to try to launch your AMI, get the ID from
the Packer output.
</div>

## Managing the Image

Packer only builds images. It does not attempt to manage them in any way.
After they're built, it is up to you to launch or destroy them as you see
fit. As a result of this, after running the above example, your AWS account
now has an AMI associated with it.

AMIs are stored in S3 by Amazon, so unless you want to be charged about $0.01
per month, you'll probably want to remove it. Remove the AMI by
first deregistering it on the [AWS AMI management page](https://console.aws.amazon.com/ec2/home?region=us-east-1#s=Images).
Next, delete the associated snapshot on the
[AWS snapshot management page](https://console.aws.amazon.com/ec2/home?region=us-east-1#s=Snapshots).

Congratulations! You've just built your first image with Packer. Although
the image was pretty useless in this case (nothing was changed about it),
this page should've given you a general idea of how Packer works, what
templates are, and how to validate and build templates into machine
images.