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Consul-Template

Introduction​

This cheat sheet provides a quick reference for some common HashiCorp Consul Template commands and concepts. Consul Template is a tool that dynamically generates configuration files based on data from HashiCorp Consul and other data sources.

Installation​

To use HashiCorp Consul Template, you need to install it on your system. Installation methods vary depending on your operating system. Refer to the official Consul Template documentation for installation instructions.

Consul Template Concepts​

Templates​

Consul Template uses templates written in a format like Go's text/template to define how configuration files should be generated.

  • Create a Consul Template:
    # Example: Generate an Nginx configuration file
    {{ range service "web" }}
    server {{ .Address }}:{{ .Port }};
    {{ end }}

Data Sources​

Consul Template fetches data from data sources such as HashiCorp Consul and Vault.

  • Define data sources in the configuration file:
    datacenter = "dc1"
    source "consul" {
      address = "localhost:8500"
    }

Reload Commands​

Consul Template can execute commands or scripts when templates are updated.

  • Define a command to execute when the template changes:
    template {
      source      = "/path/to/template.tpl"
      destination = "/etc/nginx/nginx.conf"
      command     = "service nginx reload"
    }

Watch Blocks​

Watch blocks define the data to watch and the template to apply when data changes.

  • Create a watch block to generate configuration:
    {{ range service "web" }}
    server {{ .Address }}:{{ .Port }};
    {{ end }}

Variables​

Consul Template allows you to define and use variables in templates.

  • Declare and use variables:
    {{ $myVar := "Hello, World!" }}
    {{ .Address }}:{{ .Port }} {{ $myVar }}

Consul Template Command-Line​

  • Generate configuration files based on templates:

    consul-template -config=config.hcl

  • Run Consul Template as a daemonized service:

    consul-template -config=config.hcl -daemon

  • Check the Consul Template version:

    consul-template -version

Conclusion​

This cheat sheet covers some common HashiCorp Consul Template commands and concepts. Consul Template is a versatile tool for generating dynamic configuration files based on data from Consul and other sources; refer to the official Consul Template documentation for more in-depth information and advanced usage.