Create backup file before bricking

Bypass with -nosafe

main.go

@@ -6,6 +6,8 @@ import (
 	"io"
 	"log"
 	"os"
+	"os/exec"
+	"path/filepath"
 	"sort"
 	"sync"
 	"time"
@@ -31,6 +33,7 @@ func init() {
 
 func main() {
 	percent := flag.Int("p", 20, "Percent to mangle")
+	unsafe := flag.Bool("unsafe", false, "Unsafe mode")
 	w := flag.Int("w", 8, "Workers")
 	flag.Parse()
 
@@ -48,6 +51,9 @@ func main() {
 			defer wg.Done()
 			defer func() { <-workers }()
 
+			file = filepath.Clean(file)
+			file = filepath.ToSlash(file)
+
 			log.Printf("Corrupting %s", file)
 			filehandle, err := os.OpenFile(file, os.O_RDWR, 0644)
 			if err != nil {
@@ -75,6 +81,14 @@ func main() {
 				return
 			}
 
+			if !*unsafe {
+				err := backup(file)
+				if err != nil {
+					Error.Printf("Error backing up %v: %v", file, err)
+					return
+				}
+			}
+
 			filesize := info.Size()
 			log.Printf("File size is %d bytes", filesize)
 
@@ -119,3 +133,20 @@ func selectRandomIndices(size, n int64) []int64 {
 
 	return indices
 }
+
+func backup(file string) error {
+	backupfile := file + ".bak"
+
+	_, err := os.Stat(backupfile)
+	if !os.IsNotExist(err) {
+		return fmt.Errorf("backup file %s already exists %s.bak", backupfile)
+	}
+
+	cmd := exec.Command("cp", "-a", file, backupfile)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("failed creating backup file with return %d and out %s", err, string(out))
+	}
+
+	return nil
+}