Information Technology Reference
In-Depth Information
Tip 160
Back Up Without a Time Machine Disk
When Time Machine is used on a portable Mac, such as a MacBook Air, OS
X is clever enough to realize there are times when the computer won't be
attached to the Time Machine disk (or within range of the Time Capsule).
Therefore, it temporarily backs up to the computer's hard disk, creating what
are known as
snapshots
.
With desktop Macs like the iMac, this feature isn't activated because it's
assumed the Time Machine disk will always be connected or that the computer
will always be in range of the Time Capsule. But this might not always be the
case. Perhaps you sometimes disconnect your Time Machine disk because
you temporarily need the USB port it uses for other things, for example.
Enabling Local Snapshots
If your desktop machine is not always connected, you can enable the same
local disk backup that portable Macs use. Open a Terminal window, and type
the following:
SUDO TMUTIL ENABLELOCAL
You'll need to type your password when prompted. A new snapshot will be
created within the hour, but if you're impatient, you can force one to be made
by typing the following at the Terminal window:
TMUTIL SNAPSHOT
Note that no indication is given that a snapshot is taking place. If you enter
Time Machine, snapshots are identified by gray bars in the time display
against the right side of the screen. Regular backups are colored purple.
Deactivating Local Snapshots
To deactivate the local backup feature, type the following:
SUDO TMUTIL DISABLELOCAL
All the local backup data will be deleted (this might take some time but will
take place in the background), so ensure you create a new external backup
of the system by attaching the Time Machine disk and clicking the Back Up
Now option on the Time Machine menu.
