GoogleContainerTools/skaffold · error

writing buffer contents to file

Error message

writing buffer contents to file: %w

What it means

After collecting all log messages into a bytes.Buffer, SaveLastLog flushes them with f.Write(contents.Bytes()). This error wraps a failure of that final write to the already-opened file — disk full, I/O error, device error, or the handle being invalid. The function aborts, possibly after a partial write.

Solutions

1. Check free disk space on the destination filesystem and retry after freeing space.
2. Verify the target filesystem did not transition to read-only or unmount (dmesg, mount output).
3. Write the log to a different local filesystem and retry.

if err := checkDiskSpace(filepath.Dir(fp), uint64(64<<20)); err != nil {
    return fmt.Errorf("insufficient space for %s: %w", fp, err)
}

if err := event.SaveLastLog(fp); err != nil {
    if strings.Contains(err.Error(), "writing buffer contents") {
        time.Sleep(time.Second)
        return event.SaveLastLog(fp) // one retry after transient I/O error
    }
    return err
}

When it happens

Trigger: Calling SaveLastLog when the file is opened successfully but the flush fails: disk quota exceeded, filesystem went read-only or was unmounted mid-write, or I/O errors on the underlying device.

Common situations: Small ephemeral CI disks filling up; network storage disconnecting; writing to tmpfs that exhausted its size limit; hardware/device errors.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• cannot create temp file
• failed to create manifest file
• failed to create the tmp directory
• failed to create the tmp directory
• opening file for writing manifests

AI-assisted analysis of GoogleContainerTools/skaffold@a1189de023 (2026-09-05). Data as JSON: /api/errors/1db9a047f9fe3b54. Report an issue: GitHub.

Appendix: source

Thrown at pkg/skaffold/event/v2/event.go:373

	if err != nil {
		return fmt.Errorf("opening %s: %w", fp, err)
	}
	defer f.Close()

	// Iterate over events, grabbing contents only from SkaffoldLogEvents
	var contents bytes.Buffer
	for _, ev := range handler.eventLog {
		if sle := ev.GetSkaffoldLogEvent(); sle != nil {
			// Strip ansi color sequences as this makes it easier to deal with when pasting into github issues
			if _, err = contents.WriteString(stripansi.Strip(sle.Message)); err != nil {
				return fmt.Errorf("writing string to temporary buffer: %w", err)
			}
		}
	}

	// Write contents of temporary buffer to file
	if _, err = f.Write(contents.Bytes()); err != nil {
		return fmt.Errorf("writing buffer contents to file: %w", err)
	}
	return nil
}

func lastLogFile(fp string) (string, error) {
	if fp != "" {
		return fp, nil
	}

	// last log location unspecified, use ~/.skaffold/last.log
	home, err := homedir.Dir()
	if err != nil {
		return "", fmt.Errorf("retrieving home directory: %w", err)
	}
	return filepath.Join(home, constants.DefaultSkaffoldDir, "last.log"), nil
}

View on GitHub (pinned to a1189de023)