There are various ways to configure Packer. By default Packer will use known folders,
which can be changed by using environment variables.


Configuring Packer

Packer strives to be stable and bug-free, but issues inevitably arise where
certain things may not work entirely correctly, or may not appear to work
correctly.


Debugging - Other

Debugging

Welcome to the Packer documentation! This documentation is more of a reference
guide for all available features and options in Packer. If you're just getting
started with Packer, please start with the introduction and getting started
guide instead.


Documentation

Installing Packer is simple. You can download a precompiled binary or compile
from source. This page details both methods.


Install

Installing Packer

There are a handful of terms used throughout the Packer documentation where the
meaning may not be immediately obvious if you haven't used Packer before.
Luckily, there are relatively few. This page documents all the terminology
required to understand and use Packer. The terminology is in alphabetical order
for quick referencing.


Terminology

This section describes the configuration language used to create Packer
templates.


Templates

Within the template, the builders section contains an array of all the builders
that Packer should use to generate machine images for the template.


Builders - Templates

Builders

Communicators are the mechanism Packer uses to upload files, execute scripts,
etc. with the machine being created.


Communicators - Templates

Communicators

All strings within templates are processed by a common Packer templating
engine, where variables and functions can be used to modify the value of a
configuration parameter at runtime.


Template Engine - Templates

Engine

The JSON templates are JSON files that configure the various components of Packer in order to create one or more machine images. Templates are portable, static, and readable and writable by both humans and computers. This has the added benefit of being able to not only create and modify templates by hand, but also write scripts to dynamically create or modify templates.


JSON Templates

The post-processor section within a template configures any post-processing
that will be done to images built by the builders. Examples of post-processing
would be compressing files, uploading artifacts, etc.


Post-Processors - Templates

Post-Processors

Within the template, the provisioners section contains an array of all the
provisioners that Packer should use to install and configure software within
running machines prior to turning them into machine images.


Provisioners - Templates

Provisioners

User variables allow your templates to be further configured with variables
from the command-line, environment variables, or files. This lets you
parameterize your templates so that you can keep secret tokens,
environment-specific data, and other types of information out of your
templates. This maximizes the portability and shareability of the template.


User Variables - Templates

User Variables

Special variables provide connection information and basic instance state information.
This page covers all existing special variables.

Contextual Variables - HCL Configuration Language

Contextual Variables

Data sources allow data to be fetched or computed for use elsewhere in local variables and build sources configuration. Use of data sources allows a Builder to make use of information defined outside of Packer.

Data Sources

HCL allows the use of expressions to access data exported
by sources and to transform and combine that data to produce other values.

Expressions - Configuration Language

Expressions

Packer uses text files to describe infrastructure and to set variables.
These text files are called Packer _configurations_ and are
written in the HCL2 HashiCorp Configuration Language.

HCL Templates

Local values assign a name to an expression that can then be used multiple times within a folder.

Local Values - HCL Configuration Language

Locals

Only and Except can be used as a command line argument to selectively run builds. Only and Except can also be used in a provisioner to not run it for a source.

Only Except - HCL Configuration Language

Only Except

Special variables provide directory information. This page covers all path
variables.

Path Variables - HCL Configuration Language

Path Variables

In addition to the native syntax that is most commonly used with Packer,
the HCL language can also be expressed in a JSON-compatible syntax.

JSON Configuration Syntax - Configuration Language

JSON Syntax

HCL has its own syntax, intended to combine declarative
structure with expressions in a way that is easy for humans to read and
understand.

Syntax - Configuration Language

Syntax

Input variables are parameters for Packer modules.
This page covers configuration syntax for variables.

Input Variables - HCL Configuration Language

Variables

The HCL language has a number of built-in functions that can be called
from within expressions to transform and combine values.

Functions - Configuration Language

Functions

uuid - Functions - Configuration Language

UUID Functions

The uuidv4 function generates a unique id.

v4 - uuid - Functions - Configuration Language

uuidv4

The uuidv5 function generates a uuid v5 string representation of the value in
the specified namespace.

uuidv5 - Functions - Configuration Language

uuidv5

The chomp function removes newline characters at the end of a string.

chomp - Functions - Configuration Language

chomp

The format function produces a string by formatting a number of other values
according to a specification string.

format - Functions - Configuration Language

format

The formatlist function produces a list of strings by formatting a number of
other values according to a specification string.

formatlist - Functions - Configuration Language

formatlist

The indent function adds a number of spaces to the beginnings of all but the
first line of a given multi-line string.

indent - Functions - Configuration Language

indent

string - Functions - Configuration Language

String Functions

The join function produces a string by concatenating the elements of a list
with a given delimiter.

join - Functions - Configuration Language

join

The lower function converts all cased letters in the given string to lowercase.

lower - Functions - Configuration Language

lower

The regex function applies a regular expression to a string and returns the
matching substrings.

regex - Functions - Configuration Language

regex

The regex_replace function searches a given string for another given substring,
and replaces all occurrences with a given replacement string. The substring
argument can be a valid regular expression or a string.

regex_replace - Functions - Configuration Language

regex_replace

The regexall function applies a regular expression to a string and returns a list of all matches.

regexall - Functions - Configuration Language

regexall

The replace function searches a given string for another given substring,
and replaces all occurrences with a given replacement string.

replace - Functions - Configuration Language

replace

The split function produces a list by dividing a given string at all
occurrences of a given separator.

split - Functions - Configuration Language

split

strrev - Functions - Configuration Language

strrev

The substr function extracts a substring from a given string by offset and
length.

substr - Functions - Configuration Language

substr

The title function converts the first letter of each word in a given string
to uppercase.

title - Functions - Configuration Language

title

The trim function removes the specified characters from the start and end of
a given string.

trim - Functions - Configuration Language

trim

The trimprefix function removes the specified prefix from the start of a
given string.

trimprefix - Functions - Configuration Language

trimprefix

The trimspace function removes space characters from the start and end of
a given string.

trimspace - Functions - Configuration Language

trimspace

The trimsuffix function removes the specified suffix from the end of a
given string.

trimsuffix - Functions - Configuration Language

trimsuffix

The upper function converts all cased letters in the given string to uppercase.

upper - Functions - Configuration Language

upper

The abs function returns the absolute value of the given number.

abs - Functions - Configuration Language

The ceil function returns the closest whole number greater than or equal to
the given value.

ceil - Functions - Configuration Language

ceil

The floor function returns the closest whole number less than or equal to
the given value.

floor - Functions - Configuration Language

floor

Numeric - Functions - Configuration Language

Numeric Functions

The log function returns the logarithm of a given number in a given base.

log - Functions - Configuration Language

The max function takes one or more numbers and returns the greatest number.

max - Functions - Configuration Language

The min function takes one or more numbers and returns the smallest number.

min - Functions - Configuration Language

The parseint function parses the given string as a representation of an integer.

parseint - Functions - Configuration Language

parseint

The pow function raises a number to a power.

pow - Functions - Configuration Language

The signum function determines the sign of a number.

signum - Functions - Configuration Language

signum

The cidrhost function calculates a full host IP address within a given
IP network address prefix.

cidrhost - Functions - Configuration Language

cidrhost

The cidrnetmask function converts an IPv4 address prefix given in CIDR
notation into a subnet mask address.

cidrnetmask - Functions - Configuration Language

cidrnetmask

The cidrsubnet function calculates a subnet address within a given IP network
address prefix.

cidrsubnet - Functions - Configuration Language

cidrsubnet

The cidrsubnets function calculates a sequence of consecutive IP address
ranges within a particular CIDR prefix.

cidrsubnets - Functions - Configuration Language

ipnet - Functions - Configuration Language

IP Network Functions

The abspath function converts the argument to an absolute filesystem path.

abspath - Functions - Configuration Language

abspath

The basename function removes all except the last portion from a filesystem
path.

basename - Functions - Configuration Language

basename

The dirname function removes the last portion from a filesystem path.

dirname - Functions - Configuration Language

dirname

The file function reads the contents of the file at the given path and
returns them as a string.

file - Functions - Configuration Language

file

The fileexists function determines whether a file exists at a given path.

fileexists - Functions - Configuration Language

fileexists

The fileset function enumerates a set of regular file names given a pattern.

fileset - Functions - Configuration Language

fileset

Overview of available filesystem functions

filesystem - Functions - Configuration Language

Filesystem Functions

The pathexpand function expands a leading ~ character to the current user's
home directory.