diff --git a/common/defaults.go b/common/defaults.go
new file mode 100644
index 0000000000..50ce2e4504
--- /dev/null
+++ b/common/defaults.go
@@ -0,0 +1,87 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package common
+
+import (
+	"path/filepath"
+	"runtime"
+)
+
+const (
+	DefaultIPCSocket = "geth.ipc"  // Default (relative) name of the IPC RPC socket
+	DefaultHTTPHost  = "localhost" // Default host interface for the HTTP RPC server
+	DefaultHTTPPort  = 8545        // Default TCP port for the HTTP RPC server
+	DefaultWSHost    = "localhost" // Default host interface for the websocket RPC server
+	DefaultWSPort    = 8546        // Default TCP port for the websocket RPC server
+)
+
+
+func defaultDataDirParent() string {
+	// Try to place the data folder in the user's home dir
+	home := HomeDir()
+	if home != "" {
+		if runtime.GOOS == "darwin" {
+			return filepath.Join(home, "Library")
+		} else if runtime.GOOS == "windows" {
+			return filepath.Join(home, "AppData", "Roaming")
+		} else {
+			return filepath.Join(home)
+		}
+	}
+	// As we cannot guess a stable location, return empty and handle later
+	return ""
+}
+
+func defaultClassicDataDir() string {
+	if runtime.GOOS == "darwin" {
+		return "Ellaism"
+	} else if runtime.GOOS == "windows" {
+		return "Ellaism"
+	} else {
+		return ".ellaism"
+	}
+}
+
+func defaultUnclassicDataDir() string {
+	if runtime.GOOS == "darwin" {
+		return "Ethereum"
+	} else if runtime.GOOS == "windows" {
+		return "Ethereum"
+	} else {
+		return ".ethereum"
+	}
+}
+
+// DefaultDataDir is the default data directory to use for the databases and other
+// persistence requirements.
+func DefaultDataDir() string {
+	// If the parentDir (os-specific) is available, use that.
+	if parentDir := defaultDataDirParent(); parentDir != "" {
+		return filepath.Join(parentDir, defaultClassicDataDir())
+	} else {
+		return parentDir
+	}
+}
+
+// DefaultUnclassicDataDir is the default data directory to check for preexisting unclassic persisted data.
+func DefaultUnclassicDataDir() string {
+	if parentDir := defaultDataDirParent(); parentDir != "" {
+		return filepath.Join(parentDir, defaultUnclassicDataDir())
+	} else {
+		return parentDir
+	}
+}
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