dgraph-io/badger · error

Cannot find directory %q for read-only open

Error message

Cannot find directory %q for read-only open

What it means

Returned by badger.Open/OpenDB when the configured directory does not exist and the options request read-only mode. In normal mode badger creates the directory (os.MkdirAll 0700), but a read-only open must not create anything, so it fails with this error instead.

Source

Thrown at db.go:2074

	}
}

func (db *DB) syncDir(dir string) error {
	if db.opt.InMemory {
		return nil
	}
	return syncDir(dir)
}

func createDirs(opt Options) error {
	for _, path := range []string{opt.Dir, opt.ValueDir} {
		dirExists, err := exists(path)
		if err != nil {
			return y.Wrapf(err, "Invalid Dir: %q", path)
		}
		if !dirExists {
			if opt.ReadOnly {
				return fmt.Errorf("Cannot find directory %q for read-only open", path)
			}
			// Try to create the directory
			err = os.MkdirAll(path, 0700)
			if err != nil {
				return y.Wrapf(err, "Error Creating Dir: %q", path)
			}
		}
	}
	return nil
}

// Stream the contents of this DB to a new DB with options outOptions that will be
// created in outDir.
func (db *DB) StreamDB(outOptions Options) error {
	outDir := outOptions.Dir

	// Open output DB.
	outDB, err := OpenManaged(outOptions)

View on GitHub (pinned to 2a001d466f)

Solutions

1. Create the directory before opening: os.MkdirAll(dir, 0700) then open with ReadOnly: true
2. Verify the Dir and ValueDir paths in your options are correct and the volume is mounted
3. If you control the code path, drop ReadOnly (or create the dir) when the directory is absent

Example fix

// before
db, err := badger.Open(badger.DefaultOptions(dir).WithReadOnly(true))

// after
if err := os.MkdirAll(dir, 0700); err != nil { return err }
db, err := badger.Open(badger.DefaultOptions(dir).WithReadOnly(true))

if info, err := os.Stat(dir); os.IsNotExist(err) {
    return fmt.Errorf("badger dir %q does not exist for read-only open", dir)
}

db, err := badger.Open(opts)
if err != nil && strings.Contains(err.Error(), "Cannot find directory") {
    // fail fast with clear config guidance
    return fmt.Errorf("check badger Dir/ValueDir %q and volume mounts: %w", opts.Dir, err)
}

When it happens

Trigger: Calling badger.Open (or OpenBanned/standby variants) with opt.ReadOnly = true and a Dir (or ValueDir) path that does not exist on disk — including typos, unmounted volumes, or a path that exists only after app startup creates it.

Common situations: Typo in the DB path config; mounting the data volume after the app starts; Kubernetes/container where the volume mount is missing; running a read-replica against a directory that was never created; Docker volume not mounted into the container.

Related errors

• ErrReadOnlyTxn
• ErrWindowsNotSupported
• ErrPlan9NotSupported
• ErrTruncateNeeded
• ErrGCInReadOnlyMode

AI-assisted analysis of dgraph-io/badger@2a001d466f (2026-09-05). Data as JSON: /api/errors/c7eb6de40a3b925f. Report an issue: GitHub.