vitessio/vitess · error

could not create temp file: %v

Error message

could not create temp file: %v

What it means

During a local RefreshConfig, os.CreateTemp failed to create a temporary my.cnf in the directory containing the current my.cnf. The error is wrapped from the OS and indicates filesystem-level inability to write in that directory.

Source

Thrown at go/vt/mysqlctl/mysqld.go:1570

// RefreshConfig attempts to recreate the my.cnf from templates, and log and
// swap in to place if it's updated. It keeps a copy of the last version in case fallback is required.
// Should be called from a stable replica, server_id is not regenerated.
func (mysqld *Mysqld) RefreshConfig(ctx context.Context, cnf *Mycnf) error {
	// Execute as remote action on mysqlctld if requested.
	if socketFile != "" {
		log.Info(fmt.Sprintf("executing Mysqld.RefreshConfig() remotely via mysqlctld server: %v", socketFile))
		client, err := mysqlctlclient.New(ctx, "unix", socketFile)
		if err != nil {
			return fmt.Errorf("can't dial mysqlctld: %v", err)
		}
		defer client.Close()
		return client.RefreshConfig(ctx)
	}

	log.Info("Checking for updates to my.cnf")
	f, err := os.CreateTemp(path.Dir(cnf.Path), "my.cnf")
	if err != nil {
		return fmt.Errorf("could not create temp file: %v", err)
	}

	defer os.Remove(f.Name())
	err = mysqld.initConfig(cnf, f.Name())
	if err != nil {
		return fmt.Errorf("could not initConfig in %v: %v", f.Name(), err)
	}

	existing, err := os.ReadFile(cnf.Path)
	if err != nil {
		return fmt.Errorf("could not read existing file %v: %v", cnf.Path, err)
	}
	updated, err := os.ReadFile(f.Name())
	if err != nil {
		return fmt.Errorf("could not read updated file %v: %v", f.Name(), err)
	}

	if bytes.Equal(existing, updated) {

View on GitHub (pinned to 01a25a7d17)

Solutions

1. Check the directory containing cnf.Path exists, is writable, and the disk is not full.
2. Recreate the vt tablet directory structure (init config) if VTDATAROOT was wiped.
3. Fix ownership/permissions: chown to the user running vitess.
4. Ensure the filesystem is mounted read-write.

Example fix

// before: directory missing
ls: /vt/vtdataroot/vt_0000000100: No such file or directory
// after
mkdir -p /vt/vtdataroot/vt_0000000100 && chown vitess:vitess /vt/vtdataroot/vt_0000000100

cfgDir := path.Dir(cnf.Path)
if info, err := os.Stat(cfgDir); err != nil || !info.IsDir() {
    return fmt.Errorf("config dir %s missing", cfgDir)
}
if err := unix.Access(cfgDir, unix.W_OK); err != nil {
    return fmt.Errorf("config dir %s not writable", cfgDir)
}

if err := mysqld.RefreshConfig(ctx, cnf); err != nil {
    if strings.Contains(err.Error(), "could not create temp file") {
        log.Errorf("check disk space/permissions on %s: %v", path.Dir(cnf.Path), err)
    }
    return err
}

When it happens

Trigger: Mysqld.RefreshConfig running locally (no mysqlctld socket); os.CreateTemp(path.Dir(cnf.Path), "my.cnf") fails due to missing directory, full disk, or permission denied.

Common situations: VTDATAROOT directory deleted or never created; read-only filesystem; disk full; running as a user without write permission on the config directory.

Related errors

• could not read existing file %v: %v
• cannot stat hook %v: %v
• unable to create file: %v
• could not back up existing %v: %v
• failure creating directory %s: %w

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/8175c7a11f2308a0. Report an issue: GitHub.