Gunter

Gunter is a configuration system which was created with KISS (Keep It Short and Simple) principle in mind.

Gunter takes a files and directories from the templates directory, takes a configuration data from the configuration file written in TOML language, and then create directories with the same names (without .template suffix, if exists), renders *.template files via Go template engine, and puts result to destination directory.

Non-template files and directories will by just copied to destination directory.

Of course, gunter will save file permissions including file owner uid/gid of the copied files and directories.

Installation

There is PKGBUILD file for the Arch Linux users.

On other distros gunter can be installed via go get:

go get github.com/reconquest/gunter

Usage

Options

• -t <tpl> - Set source templates directory (default: /var/gunter/templates).

• -c <config> - Set source file with configuration data (default: /etc/gunter/config).

  The contents of the configuraion file, which must be written in TOML language, will be used to render every template file.

• -d <dir> - Set destination directory, where rendered template files and directories will be saved. (default: /)

  After running gunter, resulting files and directories will be copied to destination directory with the same paths.

• -r - "Dry Run" mode. In this mode, gunter will create the temporary directory, print location, use it as destination directory and will not overwrite any system files.

  Very useful for debugging time.

• -l <log> - Write overwritten files into specified log. Works in dry-run mode too.

Templates

All template files should be written in Go template engine syntax and have the .template suffix in name.

Read more about syntax: http://golang.org/pkg/html/template/

If template file uses variables, which does not present in configuration file, gunter will exit with 1.

Tip

Go template engine do not have nice way to suppress new lines before tags like {{ end }} (github issue). And template like this:

{{ range $item := .Data.Items }}
	{{ $item }}
{{ end }}

Will be rendered to:

	item1

	item2

	item3

And it is not ok, gunter can fix this trouble using {{ - end }} tag instead of {{ end }}, and template like this:

{{ range $item := .Data.Items }}
	{{ $item }}
{{ - end }}

dash symbol prepended before 'end'

Will be rendered to:

	item1
	item2
	item3

Arbitrary example

For example, there are two services foo and bar, that requires configuration files, which are located in /etc/foo/main.conf and /etc/bar.conf.

So should create template files with filename suffix .template in template directory, for template directory, will be used /var/templates/. In this case it should /etc/foo/main.conf.template and /etc/bar.conf.template.

Service foo should be configured like this:

some_persistent_option = 1
host = {{ .Foo.Host }}
port = {{ .Foo.Port }}
another_persistent_option = 1

And service bar like this:

BarUpstream: [ {{ range $ip := .Bar.Addresses }}
        {{ $ip }}
    {{ - end }}
]

As configuration file will be used /etc/superconf, create it with contents like as following:

# describe foo service
[Foo]
Host = "node0.fo.o"
Port = 80

# and bar service
[Bar]
Addresses = [ "node0.ba.r", "node1.ba.r", "node2.ba.r" ]

Run gunter "Dry Run" mode passing -r flag.

gunter -t /var/templates/ -c /etc/superconf -r`

After running gunter will print directory where all rendered files and directories are stored:

2015/05/22 09:35:30 configuration files are saved into temporary directory
/tmp/gunter281738087/

So, structure of /tmp/gunter281738087/ will be the same as /var/templates/ with all file permissions (including file owner uid/gid):

/tmp/gunter281738087
└── etc
    ├── bar.conf
    └── foo
        └── main.conf

2 directories, 2 files

/tmp/gunter281738087/etc/foo/main.conf will have contents:

some_persistent_option = 1
host = node0.fo.o
port = 80
another_persistent_option = 1

and /tmp/gunter281738087/etc/bar.conf:

BarUpstream: [
        node0.ba.r
        node1.ba.r
        node2.ba.r
]

If result configuration files are ok, gunter can be invoked in "normal" mode and install all configurations to root system directory.

gunter -t /var/templates/ -c /etc/superconf

After that, all configuration files are directory will be copied to destination directory and services foo and bar can start using compiled configuration data.