Is Time Machine enough to completely restore my system on a new primary hard drive?

Question

I have made a Time Machine backup of my Mac Book Pro onto an external hard drive. I do not have a copy of the OS (Mountain Lion).

Is my Time Machine backup all I require if I want to reinstall my Time Machine image onto a fresh new hard drive for the MBP? Or do I need a copy of the OS as well?

I noticed that when I had my external drive with Time Machine connected to my MBP, when I held down the option button while rebooting, the external drive showed up as an option to boot from, and when I did, it seemed to allow me to do a restore, but I'm not sure if that was somehow affected because my original Mac OS partition existed. If I completely wiped my MBP hard drive (including the 200 MB partition and the Recovery Partition), or replaced it with a new hard drive, would I still be able to boot from the Time Machine image and restore everything on the hard drive?

Answer 1

The Time Machine disk isn't normally bootable, so I'm not sure why you were able to boot from it. Is it possible the disk is partitioned, and OS X is installed on another partition? Did it let you run the Finder, or just the Recovery environment?

Without knowing what's on your backup disk, it's a little hard for me to make solid recommendations; but what I'd generally recommend is to use the Recovery Disk Assistant to clone the recovery partition from your regular HD to either a flash drive (1GB or larger), or possibly a second partition on the backup disk (note that you should be able to use Disk Utility to shrink the backup partition and create a small new one beneath it).

Also, be aware that Time Machine can't restore anything it didn't back up, so if you have excluded anything from the backup, it won't be available for restoration. Also, I'm generally leery of fully trusting any single backup, so I'd recommend a second backup using a different strategy. Carbon Copy Cloner would be my first choice, but there are a large number of options.