From 73d0790e30b6ae3efe4fcc3bd10160531ef55c6d Mon Sep 17 00:00:00 2001
From: Josh Curl <josh@curl.me>
Date: Thu, 1 Sep 2016 09:56:03 -0700
Subject: [PATCH] Reduce memory usage copying Docker binaries

---
 cmd/userdocker/main.go | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/cmd/userdocker/main.go b/cmd/userdocker/main.go
index 8ba2401c..6b54ad44 100644
--- a/cmd/userdocker/main.go
+++ b/cmd/userdocker/main.go
@@ -96,11 +96,27 @@ func copyBinaries(source, dest string) error {
 		sourceFile := path.Join(source, file.Name())
 		destFile := path.Join(dest, file.Name())
 
-		data, err := ioutil.ReadFile(sourceFile)
+		in, err := os.Open(sourceFile)
 		if err != nil {
 			return err
 		}
-		if err := ioutil.WriteFile(destFile, data, 0751); err != nil {
+		out, err := os.Create(destFile)
+		if err != nil {
+			return err
+		}
+		if _, err = io.Copy(out, in); err != nil {
+			return err
+		}
+		if err = out.Sync(); err != nil {
+			return err
+		}
+		if err = in.Close(); err != nil {
+			return err
+		}
+		if err = out.Close(); err != nil {
+			return err
+		}
+		if err := os.Chmod(destFile, 0751); err != nil {
 			return err
 		}
 	}