I have a an external hard drive attached via USB to my 13 inch Mac Book Air 2011 running 10.7.4. I have Time Machine setup to backup to this drive exclusively; this hard drive serves no other purpose.
My problem is that every time I put my laptop to sleep or logout of my user and then wakeup/log back in, the hard drive icon changes from the Time Machine backup drive icon to the regular USB hard drive icon. I've noticed too that my scheduled backups have been failing:
6/20/12 5:56:06 AM: Starting standard backup 6/20/12 5:56:06 AM: Error -35 while resolving alias to backup target 6/20/12 5:56:16 AM: Backup failed with error: 19
The advice from the interwebs indicates that my hard drive needs to be in 'Time Machine mode' in order for the backup to work correctly. Up till now I've been manually initiating the backup. The other piece of my setup is that I'm using TimeMachineEditor since I don't need hourly backups; daily backups are just fine.
How do I configure Time Machine so that I my scheduled backup will work with this external drive?