package layer // import "github.com/docker/docker/layer" import ( "fmt" "io/ioutil" "os" "strings" ) // setOS writes the "os" file to the layer filestore func (fm *fileMetadataTransaction) setOS(os string) error { if os == "" { return nil } return fm.ws.WriteFile("os", []byte(os), 0644) } // getOS reads the "os" file from the layer filestore func (fms *fileMetadataStore) getOS(layer ChainID) (string, error) { contentBytes, err := ioutil.ReadFile(fms.getLayerFilename(layer, "os")) if err != nil { // For backwards compatibility, the os file may not exist. Default to "windows" if missing. if os.IsNotExist(err) { return "windows", nil } return "", err } content := strings.TrimSpace(string(contentBytes)) if content != "windows" && content != "linux" { return "", fmt.Errorf("invalid operating system value: %s", content) } return content, nil }