package chroot import ( "errors" "fmt" "os" "path/filepath" "strings" ) // AvailableDevice finds an available device and returns it. Note that // you should externally hold a flock or something in order to guarantee // that this device is available across processes. func AvailableDevice() (string, error) { prefix, err := devicePrefix() if err != nil { return "", err } letters := "fghijklmnop" for _, letter := range letters { for i := 1; i < 16; i++ { device := fmt.Sprintf("/dev/%s%c%d", prefix, letter, i) if _, err := os.Stat(device); err != nil { return device, nil } } } return "", errors.New("available device could not be found") } // devicePrefix returns the prefix ("sd" or "xvd" or so on) of the devices // on the system. func devicePrefix() (string, error) { available := []string{"sd", "xvd"} f, err := os.Open("/sys/block") if err != nil { return "", err } defer f.Close() dirs, err := f.Readdirnames(-1) if dirs != nil && len(dirs) > 0 { for _, dir := range dirs { dirBase := filepath.Base(dir) for _, prefix := range available { if strings.HasPrefix(dirBase, prefix) { return prefix, nil } } } } if err != nil { return "", err } return "", errors.New("device prefix could not be detected") }