diff --git a/cmd/ctrld/main.go b/cmd/ctrld/main.go
index 033fd2e..ff7d3d5 100644
--- a/cmd/ctrld/main.go
+++ b/cmd/ctrld/main.go
@@ -1,8 +1,8 @@
 package main
 
 import (
-	"fmt"
 	"io"
+	"log"
 	"os"
 	"path/filepath"
 	"time"
@@ -61,12 +61,16 @@ func initLogging() {
 	if logFilePath := normalizeLogFilePath(cfg.Service.LogPath); logFilePath != "" {
 		// Create parent directory if necessary.
 		if err := os.MkdirAll(filepath.Dir(logFilePath), 0750); err != nil {
-			fmt.Fprintf(os.Stderr, "failed to create log path: %v", err)
+			log.Printf("failed to create log path: %v", err)
 			os.Exit(1)
 		}
-		logFile, err := os.OpenFile(logFilePath, os.O_APPEND|os.O_CREATE|os.O_RDWR, os.FileMode(0o600))
+		// Backup old log file with .1 suffix.
+		if err := os.Rename(logFilePath, logFilePath+".1"); err != nil && !os.IsNotExist(err) {
+			log.Printf("could not backup old log file: %v", err)
+		}
+		logFile, err := os.OpenFile(logFilePath, os.O_CREATE|os.O_RDWR, os.FileMode(0o600))
 		if err != nil {
-			fmt.Fprintf(os.Stderr, "failed to create log file: %v", err)
+			log.Printf("failed to create log file: %v", err)
 			os.Exit(1)
 		}
 		writers = append(writers, logFile)