» Packer Commands (CLI)

Packer is controlled using a command-line interface. All interaction with Packer is done via the packer tool. Like many other command-line tools, the packer tool takes a subcommand to execute, and that subcommand may have additional options as well. Subcommands are executed with packer SUBCOMMAND, where "SUBCOMMAND" is the actual command you wish to execute.

If you run packer by itself, help will be displayed showing all available subcommands and a brief synopsis of what they do. In addition to this, you can run any packer command with the -h flag to output more detailed help for a specific subcommand.

In addition to the documentation available on the command-line, each command is documented on this website. You can find the documentation for a specific subcommand using the navigation to the left.

» Machine-Readable Output

By default, the output of Packer is very human-readable. It uses nice formatting, spacing, and colors in order to make Packer a pleasure to use. However, Packer was built with automation in mind. To that end, Packer supports a fully machine-readable output setting, allowing you to use Packer in automated environments.

Because the machine-readable output format was made with Unix tools in mind, it is awk/sed/grep/etc. friendly and provides a familiar interface without requiring you to learn a new format.

» Enabling Machine-Readable Output

The machine-readable output format can be enabled by passing the -machine-readable flag to any Packer command. This immediately enables all output to become machine-readable on stdout. Logging, if enabled, continues to appear on stderr. An example of the output is shown below:

$ packer -machine-readable version
1498365963,,version,1.0.2
1498365963,,version-prelease,
1498365963,,version-commit,3ead2750b+CHANGES
1498365963,,ui,say,Packer v1.0.2

The format will be covered in more detail later. But as you can see, the output immediately becomes machine-friendly. Try some other commands with the -machine-readable flag to see!

» Format for Machine-Readable Output

The machine readable format is a line-oriented, comma-delimited text format. This makes it more convenient to parse using standard Unix tools such as awk or grep in addition to full programming languages like Ruby or Python.

The format is:

timestamp,target,type,data...

Each component is explained below:

  • timestamp is a Unix timestamp in UTC of when the message was printed.

  • target is the target of the following output. This is empty if the message is related to Packer globally. Otherwise, this is generally a build name so you can relate output to a specific build while parallel builds are running.

  • type is the type of machine-readable message being outputted. There are a set of standard types which are covered later, but each component of Packer (builders, provisioners, etc.) may output their own custom types as well, allowing the machine-readable output to be infinitely flexible.

  • data is zero or more comma-separated values associated with the prior type. The exact amount and meaning of this data is type-dependent, so you must read the documentation associated with the type to understand fully.

Within the format, if data contains a comma, it is replaced with %!(PACKER_COMMA). This was preferred over an escape character such as \' because it is more friendly to tools like awk.

Newlines within the format are replaced with their respective standard escape sequence. Newlines become a literal \n within the output. Carriage returns become a literal \r.

» Machine-Readable Message Types

The set of machine-readable message types can be found in the machine-readable format complete documentation section. This section contains documentation on all the message types exposed by Packer core as well as all the components that ship with Packer by default.