Tarfs - chainguard-dev/apko

The pkg/tarfs package in the Chainguard Dev’s APKO project is used to create filesystems in memory. It is a Go package that provides an implementation of the io/fs interface using tar format. This package is used to build container images using a declarative language based on YAML.

Here are the possible options for using the pkg/tarfs package:

DirFS: This function returns a dirFS type, which is a io/fs.FS that serves the contents of a directory on the filesystem. It is suitable for use as a BaseFS. Here’s an example:

import (
"vfs"
"path/filepath"
)

func main() {
baseFS, err := vfs.DirFS(filepath.Clean("/path/to/directory"))
if err != nil {
// handle error
}
// use baseFS
}

ExpandAPK: This function expands an APK package into a memFS instance. It takes a tar.File object, a fs.FS object, and an apk.Package object as arguments. Here’s an example:

import (
"vfs"
"apk"
"io/ioutil"
"path/filepath"
)

func main() {
pkg, err := apk.NewPackage("path/to/apk/file")
if err != nil {
// handle error
}
f, err := os.Open("path/to/apk/file")
if err != nil {
// handle error
}
defer f.Close()
tf, err := ioutil.ReadAll(f)
if err != nil {
// handle error
}
tr := tar.NewReader(bytes.NewReader(tf))
baseFS, err := vfs.ExpandAPK(tr, nil, pkg)
if err != nil {
// handle error
}
// use baseFS
}

SetXattr: This function sets an extended attribute on a file in a memFS instance. It takes a file path, an attribute name, and an attribute value as arguments. Here’s an example:

import (
"vfs"
)

func main() {
baseFS, err := vfs.DirFS(filepath.Clean("/path/to/directory"))
if err != nil {
// handle error
}
err = baseFS.SetXattr("path/to/file", "user.test", []byte("test"))
if err != nil {
// handle error
}
// use baseFS
}

For more information, see the following links: