TM can not backup the drive it is located on. Since a Macbook has one internal drive, TM has to backup to an external drive. If there is no TM drive available, no backups will be made until until one is.
TM can not backup the drive it is located on. Since a Macbook has one internal drive, TM has to backup to an external drive. If there is no TM drive available, no backups will be made until until one is.