Avoid warning message when /dev/rtc does not exist

For instance the Raspberry Pi does not have any real-time clock,
so rely on network time synchronization instead (systemd-timesyncd).

Signed-off-by: Anders F Björklund <[email protected]>

Author: afbjorklund

pkg/guestagent/guestagent_linux.go

@@ -326,6 +326,10 @@ func (a *agent) fixSystemTimeSkew() {
 	for {
 		ticker := time.NewTicker(10 * time.Second)
 		for now := range ticker.C {
+			if !timesync.DeviceExists() {
+				logrus.Infof("fixSystemTimeSkew: device does not exist")
+				break
+			}
 			rtc, err := timesync.GetRTCTime()
 			if err != nil {
 				logrus.Warnf("fixSystemTimeSkew: lookup error: %s", err.Error())

pkg/guestagent/timesync/timesync_linux.go

@@ -1,6 +1,7 @@
 package timesync
 
 import (
+	"errors"
 	"os"
 	"time"
 
@@ -9,6 +10,11 @@ import (
 
 const rtc = "/dev/rtc"
 
+func DeviceExists() bool {
+	_, err := os.Stat(rtc)
+	return !errors.Is(err, os.ErrNotExist)
+}
+
 func GetRTCTime() (t time.Time, err error) {
 	f, err := os.Open(rtc)
 	if err != nil {