What causes "expected map for mountpoint" in ipfs/kubo?

Make every element of "mounts" a JSON object (map) with at least "mountpoint" and "child" keys

expected map for mountpoint

Error message

expected map for mountpoint

What it means

Inside MountDatastoreConfig, each element of the "mounts" array must itself be a map[string]any describing one mount. The error is thrown when an array element is not a map (e.g. a string, number, or nil), so no child spec or mountpoint can be read from it.

Source

Thrown at repo/fsrepo/datastores.go:109

	mounts []premount
}

type premount struct {
	ds     DatastoreConfig
	prefix ds.Key
}

// MountDatastoreConfig returns a mount DatastoreConfig from a spec.
func MountDatastoreConfig(params map[string]any) (DatastoreConfig, error) {
	var res mountDatastoreConfig
	mounts, ok := params["mounts"].([]any)
	if !ok {
		return nil, fmt.Errorf("'mounts' field is missing or not an array")
	}
	for _, iface := range mounts {
		cfg, ok := iface.(map[string]any)
		if !ok {
			return nil, fmt.Errorf("expected map for mountpoint")
		}

		child, err := AnyDatastoreConfig(cfg)
		if err != nil {
			return nil, err
		}

		prefix, found := cfg["mountpoint"]
		if !found {
			return nil, fmt.Errorf("no 'mountpoint' on mount")
		}

		res.mounts = append(res.mounts, premount{
			ds:     child,
			prefix: ds.NewKey(prefix.(string)),
		})
	}
	sort.Slice(res.mounts,

View on GitHub (pinned to 329838acdf)

Solutions

Make every element of "mounts" a JSON object (map) with at least "mountpoint" and "child" keys
Re-validate the config JSON with a schema or json.Unmarshal into map[string]any and inspect the mounts array
Remove null or placeholder entries from the mounts array

Example fix

// before
"mounts": ["flatfs"]
// after
"mounts": [{"mountpoint": "/blocks", "child": {"type": "flatfs", "path": "blocks"}}]

Defensive patterns

Strategy: validation

Validate before calling

for i, e := range params["mounts"].([]any) {
	if _, ok := e.(map[string]any); !ok {
		// fix mounts[i]: every entry must be an object
	}
}

Type guard

func isMountEntry(v any) (map[string]any, bool) {
	m, ok := v.(map[string]any)
	return m, ok
}

Try / catch

ds, err := fsrepo.MountDatastoreConfig(spec)
if err != nil {
	if strings.Contains(err.Error(), "expected map for mountpoint") {
		return fmt.Errorf("each mounts[] entry must be an object: %w", err)
	}
	return err
}

Prevention

Write each mount entry as a JSON object with mountpoint and child keys
Never abbreviate mount entries to plain strings
Validate config JSON structure before handing specs to fsrepo

When it happens

Trigger: AnyDatastoreConfig/MountDatastoreConfig spec where the "mounts" array contains non-object entries, e.g. ["flatfs"] instead of [{"type": "flatfs", ...}], or an element that is null.

Common situations: Hand-written JSON where a mount was abbreviated to a string; arrays built in code with wrong element types; truncated or corrupted config JSON producing malformed entries.

Related errors

AI-assisted analysis of ipfs/kubo@329838acdf (2026-09-03). Data as JSON: /api/errors/a4828d0bbb064361. Report an issue: GitHub.