Information Technology Reference
In-Depth Information
Tip 138
Keep Your Mac Wide Awake
If you need to leave your Mac unattended for a while but want to temporarily
stop it going into sleep mode, open a Terminal window, and type the following:
CAFFEINATE -DI
For as long as the Terminal window is open and the command is still running,
the computer won't go to sleep through inactivity, and nor will the display.
Technically you're turning off
idle
sleep mode, which occurs when OS X detects
the user hasn't done anything for a while.
To end the wakefulness, switch back to the Terminal window and hit
CONTROL
+
C
or simply close the Terminal window.
Rather than running
CAFFEINATE
indefinitely, you can specify a time limit,
although this must be specified in seconds. If you wanted your computer not
to sleep for two hours, for example, then you'd first need to work out the
number of seconds (2 hours x 60 minutes x 60 seconds = 7200 seconds) and
then specify it after the
-T
command-line option, as follows:
CAFFEINATE -DT 7200
Again, you can bring this to a premature end by using
CONTROL
+
C
or closing
the Terminal window.
Tip 139
Stress Test Your Mac's Memory
Problems with the RAM inside your computer can manifest themselves as the
random freezing of your computer or as frequent application crashes, espe-
cially when a lot of programs are open.
Most experts agree that testing memory is best done using a third-party
application called MemTest86. To run the test, you'll need to burn this to a
blank CD-R or CD-RW disc and boot from it as follows (obviously, those with
a newer Mac Mini or a MacBook Air will need an external CD-R/RW drive):
