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Overview

note

This page reflects the options available in the most recent version of Batect.

Batect uses a YAML-based configuration file.

By convention, this file is called batect.yml and is placed in the root of your project (alongside the batect script). You can use a different name or location and tell batect where to find it with the --config-file or -f option.

The following is a sample "hello world" configuration file:

containers:
my-container:
image: alpine:3.11.3
tasks:
say-hello:
description: Say hello to the nice person reading the Batect documentation
run:
container: my-container
command: echo 'Hello world!'

Run it with ./batect say-hello:

$ ./batect say-hello
Running say-hello...
my-container: running echo 'Hello world!'
Hello world!
say-hello finished with exit code 0 in 1.2s.

Get a list of available tasks with ./batect --list-tasks:

$ ./batect --list-tasks
Available tasks:
- say-hello: Say hello to the nice person reading the Batect documentation

Definition#

Configuration files are made up of the following fields:

project_name#

The name of your project. Used to label any images built.

If a project name is not provided, the project name is taken from the directory containing the configuration file. For example, if your configuration file is /home/alex/projects/my-cool-app/batect.yml and you do not provide a project name, my-cool-app will be used automatically.

Project names must be valid Docker references:

  • they must contain only:

    • lowercase letters
    • digits
    • dashes (-)
    • single consecutive periods (.)
    • one or two consecutive underscores (_)

  • they must not start or end with dashes, periods or underscores

config_variables#

Definitions for each of the config variables that are used throughout your configuration, in name: options format.

Config variable names must start with a letter and contain only letters, digits, dashes (-), periods (.) and underscores (_). They must not start with batect.

Detailed reference for config_variables

containers#

Definitions for each container, in name: options format.

Container names must be valid Docker references:

  • they must contain only:

    • lowercase letters
    • digits
    • dashes (-)
    • single consecutive periods (.)
    • one or two consecutive underscores (_)

  • they must not start or end with dashes, periods or underscores

Detailed reference for containers

include#

List of configuration files or bundles to include in this project.

This is useful for breaking up a large project into smaller files, or for sharing configuration between projects.

Detailed reference for includes

tasks#

Definitions for each task, in name: options format.

Task names must meet the following requirements:

  • they must contain only:

    • uppercase or lowercase letters
    • digits
    • dashes (-)
    • periods (.)
    • underscores (_)
    • colons (:)

  • they must start with a letter or digit

  • they must end with a letter or digit

Detailed reference for tasks

Expressions#

Some fields support expressions - references to environment variables on the host or config variables.

Detailed reference for expressions

Anchors, aliases, extensions and merging#

Batect supports YAML anchors and aliases. This allows you to specify a value in one place, and refer to it elsewhere. For example:

somewhere: &value-used-multiple-times the-value
# This is equivalent to somewhere-else: the-value
somewhere-else: *value-used-multiple-times

Anchors (&...) must be defined before they are referenced with an alias (*...).

Batect also supports extensions, which behave in an identical way, but allow you to define values before you use it for the first time. The following is equivalent to the example above:

.value-used-multiple-times: &value-used-multiple-times the-value
somewhere: *value-used-multiple-times
somewhere-else: *value-used-multiple-times

Extensions must be defined at the root level of your configuration file, and the key must start with a period (.).

Batect also supports the merge operator (<<) in maps. For example:

.common-environment: &common-environment
ENABLE_COOL_FEATURE: true
DATABASE_HOST: postgres:1234
tasks:
run-app:
run:
...
environment: *common-environment # Just uses the values in common-environment as-is
run-app-without-cool-feature:
run:
...
environment:
<< : *common-environment # Use common-environment as the basis for the environment in this task...
ENABLE_COOL_FEATURE: false # ...but override the value of ENABLE_COOL_FEATURE

You can merge a single map with <<: *other-map, or multiple maps with <<: [ *map-1, *map-2 ].

Local values take precedence over values merged into a map (regardless of the position of the << entry), and values from sources earlier in the list of maps take precedence over values from later sources. (For example, if both map-1 and map-2 define a value for PORT in the example earlier, the value in map-1 is used.)

Examples#

Examples are provided in the reference for config_variables, containers, includes and tasks, as well as on the cheat sheet.

For further examples and real-world scenarios, take a look at the sample projects.

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