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Local Shell Provisioner

Official

Type: shell-local

shell-local will run a shell script of your choosing on the machine where Packer is being run - in other words, shell-local will run the shell script on your build server, or your desktop, etc., rather than the remote/guest machine being provisioned by Packer.

The remote shell provisioner executes shell scripts on a remote machine.

Basic Example

The example below is fully functional.

source "file" "example" {
    content = "example content"
}

build {
  source "source.file.example" {
    target = "./test_artifact.txt"
  }

  provisioner "shell-local" {
    inline = ["echo foo"]
  }
}

Configuration Reference

The reference of available configuration options is listed below. The only required element is command.

Exactly one of the following is required:

  • command (string) - This is a single command to execute. It will be written to a temporary file and run using the execute_command call below. If you are building a Windows VM on AWS, Azure, Google Compute, or OpenStack and would like to access the generated password that Packer uses to connect to the instance via WinRM, you can use the template variable {{.WinRMPassword}} to set this as an environment variable.

  • inline (array of strings) - This is an array of commands to execute. The commands are concatenated by newlines and turned into a single file, so they are all executed within the same context. This allows you to change directories in one command and use something in the directory in the next and so on. Inline scripts are the easiest way to pull off simple tasks within the machine in which Packer is running.

  • script (string) - The path to a script to execute. This path can be absolute or relative. If it is relative, it is relative to the working directory when Packer is executed.

  • scripts (array of strings) - An array of scripts to execute. The scripts will be executed in the order specified. Each script is executed in isolation, so state such as variables from one script won't carry on to the next.

Optional parameters:

  • env (map of strings) - A map of key/value pairs to inject prior to the execute_command. Packer injects some environmental variables by default into the environment, as well, which are covered in the section below. Duplicate env settings override environment_vars settings.

  • environment_vars (array of strings) - An array of key/value pairs to inject prior to the execute_command. The format should be key=value. Packer injects some environmental variables by default into the environment, as well, which are covered in the section below. If you are building a Windows VM on AWS, Azure, Google Compute, or OpenStack and would like to access the generated password that Packer uses to connect to the instance via WinRM, you can use the template variable {{.WinRMPassword}} to set this as an environment variable. For example: "environment_vars": "WINRMPASS={{.WinRMPassword}}"

  • env_var_format (string) - When we parse the environment_vars that you provide, this gives us a string template to use in order to make sure that we are setting the environment vars correctly. By default on Windows hosts this format is set %s=%s && and on Unix, it is %s='%s'. You probably won't need to change this format, but you can see usage examples for where it is necessary below.

  • execute_command (array of strings) - The command used to execute the script. By default this is ["/bin/sh", "-c", "{{.Vars}}", "{{.Script}}"] on Unix and ["cmd", "/c", "{{.Vars}}", "{{.Script}}"] on Windows. This is treated as a template engine. There are two available variables: Script, which is the path to the script to run, and Vars, which is the list of environment_vars, if configured.

    If you choose to set this option, make sure that the first element in the array is the shell program you want to use (for example, "sh"), and a later element in the array must be {{.Script}}.

    This option provides you a great deal of flexibility. You may choose to provide your own shell program, for example "/usr/local/bin/zsh" or even "powershell.exe". However, with great power comes great responsibility - these commands are not officially supported and things like environment variables may not work if you use a different shell than the default.

    For backwards compatibility, you may also use {{.Command}}, but it is decoded the same way as {{.Script}}. We recommend using {{.Script}} for the sake of clarity, as even when you set only a single command to run, Packer writes it to a temporary file and then runs it as a script.

    If you are building a Windows VM on AWS, Azure, Google Compute, or OpenStack and would like to access the generated password that Packer uses to connect to the instance via WinRM, you can use the template variable {{.WinRMPassword}} to set this as an environment variable.

  • inline_shebang (string) - The shebang value to use when running commands specified by inline. By default, this is /bin/sh -e. If you're not using inline, then this configuration has no effect. Important: If you customize this, be sure to include something like the -e flag, otherwise individual steps failing won't fail the provisioner.

  • only_on (array of strings) - This is an array of runtime operating systems where shell-local will execute. This allows you to execute shell-local only on specific operating systems. By default, shell-local will always run if only_on is not set."

  • use_linux_pathing (bool) - This is only relevant to Windows hosts. If you are running Packer in a Windows environment with the Windows Subsystem for Linux feature enabled, and would like to invoke a bash script rather than invoking a Cmd script, you'll need to set this flag to true; it tells Packer to use the Linux subsystem path for your script rather than the Windows path. (e.g. /mnt/c/path/to/your/file instead of C:/path/to/your/file). Please see the example below for more guidance on how to use this feature. If you are not on a Windows host, or you do not intend to use the shell-local provisioner to run a bash script, please ignore this option.

  • valid_exit_codes (list of ints) - Valid exit codes for the script. By default this is 0.

Parameters common to all provisioners:

  • pause_before (duration) - Sleep for duration before execution.

  • max_retries (int) - Max times the provisioner will retry in case of failure. Defaults to zero (0). Zero means an error will not be retried.

  • only (array of string) - Only run the provisioner for listed builder(s) by name.

  • override (object) - Override the builder with different settings for a specific builder, eg :

    In HCL2:

    source "null" "example1" {
  communicator = "none"
}

source "null" "example2" {
  communicator = "none"
}

build {
  sources = ["source.null.example1", "source.null.example2"]
  provisioner "shell-local" {
    inline = ["echo not overridden"]
    override = {
      example1 = {
        inline = ["echo yes overridden"]
      }
    }
  }
}

    In JSON:

    {
  "builders": [
    {
      "type": "null",
      "name": "example1",
      "communicator": "none"
    },
    {
      "type": "null",
      "name": "example2",
      "communicator": "none"
    }
  ],
  "provisioners": [
    {
      "type": "shell-local",
      "inline": ["echo not overridden"],
      "override": {
        "example1": {
          "inline": ["echo yes overridden"]
        }
      }
    }
  ]
}

  • timeout (duration) - If the provisioner takes more than for example 1h10m1s or 10m to finish, the provisioner will timeout and fail.

Execute Command

To many new users, the execute_command is puzzling. However, it provides an important function: customization of how the command is executed. The most common use case for this is dealing with sudo password prompts. You may also need to customize this if you use a non-POSIX shell, such as tcsh on FreeBSD.

The Windows Linux Subsystem

The shell-local provisioner was designed with the idea of allowing you to run commands in your local operating system's native shell. For Windows, we've assumed in our defaults that this is Cmd. However, it is possible to run a bash script as part of the Windows Linux Subsystem from the shell-local provisioner, by modifying the execute_command and the use_linux_pathing options in the provisioner config.

The example below is a fully functional test config.

One limitation of this offering is that "inline" and "command" options are not available to you; please limit yourself to using the "script" or "scripts" options instead.

Please note that the WSL is a beta feature, and this tool is not guaranteed to work as you expect it to.

source "null" "example" {
    communicator = "none"
}

build {
    sources = [
        "source.null.example"
    ]

    provisioner "shell-local"{
        environment_vars = ["PROVISIONERTEST=ProvisionerTest1"]
        execute_command = ["bash", "-c", "{{.Vars}} {{.Script}}"]
        use_linux_pathing = true
        scripts = ["C:/Users/me/scripts/example_bash.sh"]
    }
    provisioner "shell-local"{
        environment_vars = ["PROVISIONERTEST=ProvisionerTest2"]
        execute_command = ["bash", "-c", "{{.Vars}} {{.Script}}"]
        use_linux_pathing = true
        script = "C:/Users/me/scripts/example_bash.sh"
    }
}

Default Environmental Variables

In addition to being able to specify custom environmental variables using the environment_vars configuration, the provisioner automatically defines certain commonly useful environmental variables:

  • PACKER_BUILD_NAME is set to the name of the build that Packer is running. This is most useful when Packer is making multiple builds and you want to distinguish them slightly from a common provisioning script.

  • PACKER_BUILDER_TYPE is the type of the builder that was used to create the machine that the script is running on. This is useful if you want to run only certain parts of the script on systems built with certain builders.

  • PACKER_HTTP_ADDR If using a builder that provides an HTTP server for file transfer (such as hyperv, parallels, qemu, virtualbox, and vmware), this will be set to the address. You can use this address in your provisioner to download large files over HTTP. This may be useful if you're experiencing slower speeds using the default file provisioner. A file provisioner using the winrm communicator may experience these types of difficulties.

Safely Writing A Script

Whether you use the inline option, or pass it a direct script or scripts, it is important to understand a few things about how the shell-local provisioner works to run it safely and easily. This understanding will save you much time in the process.

Once Per Builder

The shell-local script(s) you pass are run once per builder. That means that if you have an amazon-ebs builder and a docker builder, your script will be run twice. If you have 3 builders, it will run 3 times, once for each builder.

Always Exit Intentionally

If any provisioner fails, the packer build stops and all interim artifacts are cleaned up.

For a shell script, that means the script must exit with a zero code. You must be extra careful to exit 0 when necessary.

Usage Examples:

Windows Host

Example of running a .cmd file on Windows:

provisioner "shell-local" {
  environment_vars = ["SHELLLOCALTEST=ShellTest1"]
  scripts          = ["./scripts/test_cmd.cmd"]
}

Contents of "test_cmd.cmd":

echo %SHELLLOCALTEST%

Example of running an inline command on Windows: Required customization: tempfile_extension

provisioner "shell-local" {
  environment_vars   = ["SHELLLOCALTEST=ShellTest2"],
  tempfile_extension = ".cmd",
  inline             = [echo "%SHELLLOCALTEST%"]
}

Example of running a bash command on Windows using WSL: Required customizations: use_linux_pathing and execute_command

provisioner "shell-local" {
  environment_vars  = ["SHELLLOCALTEST=ShellTest3"],
  execute_command   = ["bash", "-c", "{{.Vars}} {{.Script}}"]
  use_linux_pathing = true
  script            = "./scripts/example_bash.sh"
}

Contents of example_bash.sh:

#!/bin/bash
echo $SHELLLOCALTEST

Example of running a PowerShell script on Windows: Required customizations: env_var_format and execute_command

provisioner "shell-local" {
  environment_vars = ["SHELLLOCALTEST=ShellTest4"]
  execute_command  = ["powershell.exe", "{{.Vars}} {{.Script}}"]
  env_var_format   = "$env:%s=\"%s\"; "
  script           = "./scripts/example_ps.ps1"
}

Example of running a PowerShell script on Windows as "inline": Required customizations: env_var_format, tempfile_extension, and execute_command

provisioner "shell-local" {
  tempfile_extension = ".ps1"
  environment_vars   = ["SHELLLOCALTEST=ShellTest5"]
  execute_command    = ["powershell.exe", "{{.Vars}} {{.Script}}"]
  env_var_format     = "$env:%s=\"%s\"; "
  inline             = ["write-output $env:SHELLLOCALTEST"]
}

Unix Host

Example of running a Shell script on Unix:

provisioner "shell-local" {
  environment_vars = ["PROVISIONERTEST=ProvisionerTest1"]
  scripts          = ["./scripts/example_bash.sh"]
}

Example of running a Shell script "inline" on Unix:

provisioner "shell-local" {
  environment_vars = ["PROVISIONERTEST=ProvisionerTest2"]
  inline           = ["echo hello", "echo $PROVISIONERTEST"]
}

Example of running a Python script on Unix:

provisioner "shell-local" {
  script = "hello.py"
  environment_vars = ["HELLO_USER=packeruser"]
  execute_command  = [
    "/bin/sh",
    "-c",
    "{{.Vars}} /usr/local/bin/python {{.Script}}"
  ]
}


Where "hello.py" contains:

    import os

    print('Hello, %s!' % os.getenv("HELLO_USER"))
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