github.com/marksheahan/packer@v0.10.2-0.20160613200515-1acb2d6645a0/website/source/intro/getting-started/provision.html.md (about) 1 --- 2 description: | 3 In the previous page of this guide, you created your first image with Packer. 4 The image you just built, however, was basically just a repackaging of a 5 previously existing base AMI. The real utility of Packer comes from being able 6 to install and configure software into the images as well. This stage is also 7 known as the *provision* step. Packer fully supports automated provisioning in 8 order to install software onto the machines prior to turning them into images. 9 layout: intro 10 next_title: Parallel Builds 11 next_url: '/intro/getting-started/parallel-builds.html' 12 page_title: Provision 13 prev_url: '/intro/getting-started/build-image.html' 14 ... 15 16 # Provision 17 18 In the previous page of this guide, you created your first image with Packer. 19 The image you just built, however, was basically just a repackaging of a 20 previously existing base AMI. The real utility of Packer comes from being able 21 to install and configure software into the images as well. This stage is also 22 known as the *provision* step. Packer fully supports automated provisioning in 23 order to install software onto the machines prior to turning them into images. 24 25 In this section, we're going to complete our image by installing Redis on it. 26 This way, the image we end up building actually contains Redis pre-installed. 27 Although Redis is a small, simple example, this should give you an idea of what 28 it may be like to install many more packages into the image. 29 30 Historically, pre-baked images have been frowned upon because changing them has 31 been so tedious and slow. Because Packer is completely automated, including 32 provisioning, images can be changed quickly and integrated with modern 33 configuration management tools such as Chef or Puppet. 34 35 ## Configuring Provisioners 36 37 Provisioners are configured as part of the template. We'll use the built-in 38 shell provisioner that comes with Packer to install Redis. Modify the 39 `example.json` template we made previously and add the following. We'll explain 40 the various parts of the new configuration following the code block below. 41 42 ``` {.javascript} 43 { 44 "variables": ["..."], 45 "builders": ["..."], 46 47 "provisioners": [{ 48 "type": "shell", 49 "inline": [ 50 "sleep 30", 51 "sudo apt-get update", 52 "sudo apt-get install -y redis-server" 53 ] 54 }] 55 } 56 ``` 57 58 -> **Note:** The `sleep 30` in the example above is very important. Because 59 Packer is able to detect and SSH into the instance as soon as SSH is available, 60 Ubuntu actually doesn't get proper amounts of time to initialize. The sleep 61 makes sure that the OS properly initializes. 62 63 Hopefully it is obvious, but the `builders` section shouldn't actually contain 64 "...", it should be the contents setup in the previous page of the getting 65 started guide. Also note the comma after the `"builders": [...]` section, which 66 was not present in the previous lesson. 67 68 To configure the provisioners, we add a new section `provisioners` to the 69 template, alongside the `builders` configuration. The provisioners section is an 70 array of provisioners to run. If multiple provisioners are specified, they are 71 run in the order given. 72 73 By default, each provisioner is run for every builder defined. So if we had two 74 builders defined in our template, such as both Amazon and DigitalOcean, then the 75 shell script would run as part of both builds. There are ways to restrict 76 provisioners to certain builds, but it is outside the scope of this getting 77 started guide. It is covered in more detail in the complete 78 [documentation](/docs). 79 80 The one provisioner we defined has a type of `shell`. This provisioner ships 81 with Packer and runs shell scripts on the running machine. In our case, we 82 specify two inline commands to run in order to install Redis. 83 84 ## Build 85 86 With the provisioner configured, give it a pass once again through 87 `packer validate` to verify everything is okay, then build it using 88 `packer build example.json`. The output should look similar to when you built 89 your first image, except this time there will be a new step where the 90 provisioning is run. 91 92 The output from the provisioner is too verbose to include in this guide, since 93 it contains all the output from the shell scripts. But you should see Redis 94 successfully install. After that, Packer once again turns the machine into an 95 AMI. 96 97 If you were to launch this AMI, Redis would be pre-installed. Cool! 98 99 This is just a basic example. In a real world use case, you may be provisioning 100 an image with the entire stack necessary to run your application. Or maybe just 101 the web stack so that you can have an image for web servers pre-built. This 102 saves tons of time later as you launch these images since everything is 103 pre-installed. Additionally, since everything is pre-installed, you can test the 104 images as they're built and know that when they go into production, they'll be 105 functional.