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https://github.com/dontlaugh/packer-plugin-cue
Render files in your Packer builds with CUE
https://github.com/dontlaugh/packer-plugin-cue
cue packer packer-plugin packer-provisioner
Last synced: 3 months ago
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Render files in your Packer builds with CUE
- Host: GitHub
- URL: https://github.com/dontlaugh/packer-plugin-cue
- Owner: dontlaugh
- License: mpl-2.0
- Created: 2022-10-07T21:14:20.000Z (about 2 years ago)
- Default Branch: main
- Last Pushed: 2024-06-14T21:51:22.000Z (5 months ago)
- Last Synced: 2024-06-15T04:36:12.320Z (5 months ago)
- Topics: cue, packer, packer-plugin, packer-provisioner
- Language: Go
- Homepage:
- Size: 95.7 KB
- Stars: 4
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
- awesome-cue - packer-plugin-cue - Render files in your Packer builds with CUE. (Projects)
README
# packer-plugin-cue
A packer plugin that writes files to the image you're provisioning, based
on values extracted from a CUE module.
A Packer data provider is TODO.
## Provided Plugins
Provisioners:
* `cue-export` - Given a module, package, and an optional CUE expression, the
provisioner writes a file with the scalar value or struct yielded by `cue export`.
## Example Usage
Add this plugin to `required_plugins`
```hcl
packer {
required_plugins {
cue = {
version = ">=0.3.1"
source = "github.com/dontlaugh/cue"
}
}
}
```
Write the data yielded by the expression `world` in package `hello` to **/tmp/some-file**
```hcl
provisioner "cue-export" {
dir = "."
package = "hello"
expression = "world"
dest = "/tmp/some-file"
}
```
## Config Attributes
Provisioners:
`cue-export`
* dir - path to where the CUE evaluation should take place
* module - (optional) name of module
* package - (optional) package name, if required to disambiguate
* expression - (optional) CUE expression that yields a specific package value
* dest - path to destination file; Note that some Packer builders
will not automatically create ancestor directories.
* tags - (optional) list of strings of the form `key=value`
## Explanation
Let's say you have a CUE module with a file **my_service.cue** that looks like this
```cue
package systemd
config_file: "/etc/my-service/config.yaml"
unit_file: '''
[Unit]
Description=My example service
[Service]
Environment=MY_CONFIG=\(config_file)
ExecStart=/usr/bin/my-service
[Install]
WantedBy=multi-user.target
'''
```
Invoking `cue export -p systemd ./my_service.cue` gives you the entire package as JSON
```json
{
"config_file": "/etc/my-service/config.yaml",
"unit_file": "W1VuaXRdCkRlc2N...=="
}
```
_Note: We've elided most of the unit file's base64 string here._
Providing `--out binary` and `-e unit_file` lets us select the `unit_file`
field and render it. The value of `config_file` is interpolated.
```
$ cue export -p systemd -e unit_file --out binary ./my_service.cue
[Unit]
Description=My example service
[Service]
Environment=MY_CONFIG=/etc/my-service/config.yaml
ExecStart=/usr/bin/my-service
[Install]
WantedBy=multi-user.target
```
This manner of templating files and interpolating values is useful for machine
image provisioning, and this plugin provides a declarative API for rendering CUE
to files during a Packer build.
The previous examples use the `cue` CLI, which you should definitely download
and experiment with if you are unfamiliar with CUE. This plugin, however, uses
CUE as a Go library.
### But wait, there's more!
The `cue-export` provisioner doesn't need a string or binary template to write
files. If the package (with optional expression) evaluates to a string, number,
or struct type, this plugin does the following
* String and number types are written as a single-line file to `dest`
* Struct types must be given a `serialize` config, one of "json", "yaml",
or "toml". The entire struct will be serialized in tha format.
A quick example of a struct rendered to yaml
```hcl
provisioner "cue-export" {
module = "."
dir = "."
package = "prometheus"
expression = "config_yaml"
serialize = "yaml"
dest = "/tmp/prometheus.yaml"
}
```
If your expression evaluates to a struct and no serializer is set, it's an error.