diff --git a/internal/bsr/internal/fs/fs.go b/internal/bsr/internal/fs/fs.go
new file mode 100644
index 000000000..fe51f296f
--- /dev/null
+++ b/internal/bsr/internal/fs/fs.go
@@ -0,0 +1,71 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+// Package fs defines the interfaces bsr needs with a storage system.
+package fs
+
+import (
+	"context"
+	"io"
+	"io/fs"
+)
+
+// FS is a filesystem for creating or reading BSRs.
+type FS interface {
+	New(context.Context, string) (Container, error)
+}
+
+// SyncMode is use to determine how a file is synced when closed.
+type SyncMode uint8
+
+// Valid sync modes.
+const (
+	Asynchronous SyncMode = iota
+	Synchronous
+	NoSync
+)
+
+// GetOpts - iterate the inbound Options and return a struct.
+func GetOpts(opt ...Option) Options {
+	opts := getDefaultOptions()
+	for _, o := range opt {
+		o(&opts)
+	}
+	return opts
+}
+
+func getDefaultOptions() Options {
+	return Options{
+		WithCloseSyncMode: Asynchronous,
+	}
+}
+
+// Options are fs options.
+type Options struct {
+	WithCloseSyncMode SyncMode
+}
+
+// Option is an fs option.
+type Option func(*Options)
+
+// WithCloseSyncMode sets how a file is synced when closed.
+func WithCloseSyncMode(m SyncMode) Option {
+	return func(o *Options) {
+		o.WithCloseSyncMode = m
+	}
+}
+
+// A Container is a filesystem abstraction that can create files or other containers.
+type Container interface {
+	io.Closer
+	Create(context.Context, string) (WriterFile, error)
+	OpenFile(context.Context, string, ...Option) (WriterFile, error)
+	SubContainer(context.Context, string) (Container, error)
+}
+
+// WriterFile is a file that can be written to.
+type WriterFile interface {
+	fs.File
+	io.Writer
+	io.StringWriter
+}