122 lines
3.9 KiB
Plaintext
122 lines
3.9 KiB
Plaintext
---
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page_title: packer - Blocks
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description: |-
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The "packer" configuration section is used to configure some behaviors
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of Packer itself.
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---
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# Packer Settings
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`@include 'from-1.5/beta-hcl2-note.mdx'`
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-> **Note:** The `packer` block is only available in Packer v1.6.5 and later.
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The `packer` configuration block type is used to configure some
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behaviors of Packer itself, such as the minimum required Packer version needed to
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apply your configuration.
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## Packer Block Syntax
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Packer settings are gathered together into `packer` blocks:
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```hcl
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packer {
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# ...
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}
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```
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Each `packer` block can contain a number of settings related to Packer's
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behavior. Within a `packer` block, only constant values can be used;
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arguments may not refer to named objects such as resources, input variables,
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etc, and may not use any of the Packer language built-in functions.
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The various options supported within a `packer` block are described in the
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following sections.
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## Specifying a Required Packer Version
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The `required_version` setting accepts a [version constraint
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string,](#version-constraints) which specifies which versions of Packer
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can be used with your configuration.
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If the running version of Packer doesn't match the constraints specified,
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Packer will produce an error and exit without taking any further actions.
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Use Packer version constraints in a collaborative environment to
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ensure that everyone is using a specific Packer version, or using at least
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a minimum Packer version that has behavior expected by the configuration.
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## Specifying Plugin Requirements
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-> **Note:** The `required_plugins` block is only available in Packer v1.7.0 and
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later.
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The `required_plugins` block specifies all of the plugins required by the
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current config, mapping each local plugin name to a source address and a
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version constraint.
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```hcl
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packer {
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required_plugins {
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happycloud = {
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version = ">= 2.7.0"
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source = "github.com/hashicorp/happycloud"
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}
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}
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}
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```
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For more information, see [Plugins](/docs/plugins).
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## Version Constraints
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Anywhere that Packer lets you specify a range of acceptable versions for
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something, it expects a specially formatted string known as a version
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constraint.
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### Version Constraint Syntax
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Packer's syntax for version constraints is very similar to the syntax used by
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other dependency management systems like Bundler and NPM.
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```hcl
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required_version = ">= 1.2.0, < 2.0.0"
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```
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A version constraint is a [string literal](/docs/templates/hcl_templates/expressions#string-literals)
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containing one or more conditions, which are separated by commas.
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Each condition consists of an operator and a version number.
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Version numbers should be a series of numbers separated by periods (like
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`1.2.0`), optionally with a suffix to indicate a beta release.
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The following operators are valid:
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- `=` (or no operator): Allows only one exact version number. Cannot be combined
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with other conditions.
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- `!=`: Excludes an exact version number.
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- `>`, `>=`, `<`, `<=`: Comparisons against a specified version, allowing
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versions for which the comparison is true. "Greater-than" requests newer
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versions, and "less-than" requests older versions.
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- `~>`: Allows the specified version, plus newer versions that only
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increase the _most specific_ segment of the specified version number. For
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example, `~> 0.9` is equivalent to `>= 0.9, < 1.0`, and `~> 0.8.4`, is
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equivalent to `>= 0.8.4, < 0.9`. This is usually called the pessimistic
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constraint operator.
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### Version Constraint Behavior
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A version number that meets every applicable constraint is considered acceptable.
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Packer consults version constraints to determine whether it has acceptable
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versions of itself.
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A prerelease version is a version number that contains a suffix introduced by
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a dash, like `1.2.0-beta`. A prerelease version can be selected only by an
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_exact_ version constraint (the `=` operator or no operator). Prerelease
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versions do not match inexact operators such as `>=`, `~>`, etc.
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