fix docker uptime

host/host_linux.go

@@ -109,6 +109,7 @@ func BootTimeWithContext(ctx context.Context) (uint64, error) {
 	if err != nil {
 		return 0, err
 	}
+
 	statFile := "stat"
 	if system == "lxc" && role == "guest" {
 		// if lxc, /proc/uptime is used.
@@ -123,6 +124,8 @@ func BootTimeWithContext(ctx context.Context) (uint64, error) {
 	if err != nil {
 		return 0, err
 	}
+
+	if statFile == "stat" {
 		for _, line := range lines {
 			if strings.HasPrefix(line, "btime") {
 				f := strings.Fields(line)
@@ -138,6 +141,19 @@ func BootTimeWithContext(ctx context.Context) (uint64, error) {
 				return t, nil
 			}
 		}
+	} else if statFile == "uptime" {
+		if len(lines) != 1 {
+			return 0, fmt.Errorf("wrong uptime format")
+		}
+		f := strings.Fields(lines[0])
+		b, err := strconv.ParseInt(f[0], 10, 64)
+		if err != nil {
+			return 0, err
+		}
+		t = uint64(time.Now().Unix()) - uint64(b)
+		atomic.StoreUint64(&cachedBootTime, t)
+		return t, nil
+	}
 
 	return 0, fmt.Errorf("could not find btime")
 }