juicedata/juicefs · error

failed to create plain backup %s: %w

Error message

failed to create plain backup %s: %w

What it means

When converting a (possibly encrypted/binary) backup to plain JSON, `convert` creates the destination plain-backup file with os.Create(nPath). If creation fails, the error is wrapped as `failed to create plain backup <nPath>: <error>`. This is a local filesystem write failure before any data is copied.

Source

Thrown at cmd/load.go:178

	if key == "" && !isCompress {
		return path, nil
	}

	nPath := path[:strings.LastIndex(path, ".")]
	if utils.Exists(nPath) {
		logger.Infof("plain backup %q already exists, skip conversion", nPath)
		return nPath, nil
	}

	r, err := open(path, key, algo)
	if err != nil {
		return "", err
	}
	defer r.Close()

	w, err := os.Create(nPath)
	if err != nil {
		return "", fmt.Errorf("failed to create plain backup %s: %w", nPath, err)
	}
	defer w.Close()

	if _, err = io.Copy(w, r); err != nil {
		return "", fmt.Errorf("failed to convert %s to %s: %w", path, nPath, err)
	}
	logger.Infof("converted backup %q to %q", path, nPath)
	return nPath, nil
}

func load(ctx *cli.Context) error {
	setup0(ctx, 1, 2)

	key, algo := ctx.String("encrypt-rsa-key"), ctx.String("encrypt-algo")
	src := ctx.Args().Get(1)
	var err error
	if ctx.Bool("binary") {
		if ctx.Bool("stat") {

View on GitHub (pinned to c9a67b23e8)

Solutions

1. Check that the destination directory exists and is writable (`ls -ld $(dirname <nPath>)`)
2. Free disk space if the filesystem is full (df -h)
3. Run as a user with write permission on the destination, or pick another output path
4. Check dmesg/audit logs for read-only remounts or LSM denials

Example fix

// before
juicefs load meta.sqlite3 backup.json --output /root/jfs/converted.json   # non-root user
// after
juicefs load meta.sqlite3 backup.json --output ~/converted.json

dir := filepath.Dir(nPath)
if fi, err := os.Stat(dir); err != nil || !fi.IsDir() {
    return fmt.Errorf("output dir missing: %s", dir)
}
if err := unix.Access(dir, unix.W_OK); err != nil {
    return fmt.Errorf("output dir not writable: %s", dir)
}

if err := convert(path, nPath); err != nil {
    var pe *fs.PathError
    if strings.Contains(err.Error(), "failed to create plain backup") {
        log.Fatalf("fix destination dir/permissions: %v", err)
    }
}

When it happens

Trigger: os.Create fails because the target directory does not exist, the path is a directory, the disk is full, or the process lacks write permission on the destination (e.g. / or a read-only mount as nPath's directory).

Common situations: Redirecting converted output into a read-only volume; SELinux/AppArmor denials; running as non-root while writing to /var/lib/juicefs; typo'd directory in the target path.

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

• failed to open file %s: %w
• name is required
• Could not get a FileSystem
• Cannot get file system.
• Cannot create file system.

AI-assisted analysis of juicedata/juicefs@c9a67b23e8 (2026-09-06). Data as JSON: /api/errors/de8fe2601df14a64. Report an issue: GitHub.