What causes "no 'create file' permissions" in valyala/fasthttp?

Enable index generation (fasthttp.Fs.GenerateIndexPages = true) if listings are desired

no 'create file' permissions

Error message

no 'create file' permissions

What it means

errNoCreatePermission indicates the handler is not permitted to create files — specifically the auto-generated directory index — because CreateIndexPages (or equivalent permission) is disabled. fasthttp refuses to write generated content to disk in this configuration.

Source

Thrown at fs.go:1565

				"Allow write access to the directory with this file in order to improve fasthttp performance", indexFilePath)
			mustCompress = false
			return h.openFSFile(indexFilePath, mustCompress, fileEncoding)
		}
		if !errors.Is(err, fs.ErrNotExist) {
			return nil, fmt.Errorf("cannot open file %q: %w", indexFilePath, err)
		}
	}

	if !h.generateIndexPages {
		return nil, fmt.Errorf("cannot access directory without index page: directory %q", dirPath)
	}

	return h.createDirIndex(ctx, dirPath, mustCompress, fileEncoding)
}

var (
	errDirIndexRequired   = errors.New("directory index required")
	errNoCreatePermission = errors.New("no 'create file' permissions")
)

func (h *fsHandler) createDirIndex(ctx *RequestCtx, dirPath string, mustCompress bool, fileEncoding string) (*fsFile, error) {
	w := &bytebufferpool.ByteBuffer{}

	base := ctx.URI()

	// io/fs doesn't support ReadDir with empty path.
	if dirPath == "" {
		dirPath = "."
	}

	basePathEscaped := html.EscapeString(string(base.Path()))
	_, _ = fmt.Fprintf(w, "<html><head><title>%s</title><style>.dir { font-weight: bold }</style></head><body>", basePathEscaped)
	_, _ = fmt.Fprintf(w, "<h1>%s</h1>", basePathEscaped)
	_, _ = fmt.Fprintf(w, "<ul>")

	if len(basePathEscaped) > 1 {

View on GitHub (pinned to c96f600972)

Solutions

Enable index generation (fasthttp.Fs.GenerateIndexPages = true) if listings are desired
Provide a static index file and register it via IndexNames so no generation is needed
Disable directory browsing intentionally and return 403/404 for directory URLs by handling the error yourself
Serve an explicit file path instead of a directory

Example fix

// before
fsHandler := h.fs.NewRequestHandler() // GenerateIndexPages=false, dir request -> refusal
// after
h.fs.GenerateIndexPages = true
// or: h.fs.IndexNames = []string{"index.html"}

Defensive patterns

Strategy: validation

Validate before calling

if !h.fs.GenerateIndexPages && len(h.fs.IndexNames) == 0 {
    // directory requests will be refused; register an index or enable generation
}

Try / catch

if err != nil && strings.Contains(err.Error(), "create file") {
    ctx.Error("directory listing not available", fasthttp.StatusForbidden)
}

Prevention

Enable GenerateIndexPages only on writable, trusted roots
Prefer static index files over on-the-fly generation in production
Decide explicitly whether directory browsing is allowed and encode it in config
Check filesystem write permissions for the fasthttp process when generation is on

When it happens

Trigger: A directory request requires building/caching a directory index, but the fsHandler is configured without permission to create the index file (index generation disabled), so this sentinel is returned.

Common situations: Production configs with GenerateIndexPages=false where clients request bare directory URLs; deploying read-only static servers and expecting listings; typos in IndexNames leaving no index file to serve.

Related errors

AI-assisted analysis of valyala/fasthttp@c96f600972 (2026-08-31). Data as JSON: /api/errors/f668b701f87f59b6. Report an issue: GitHub.