does a mac perform self diagnostics during sleep mode?
does a mac perform self diagnostics during sleep mode? I was told it does about 10 years ago.
Your Mac has to be turned on to run the diagnostics. See > http://pondini.org/OSX/Scripts.html
14 replies
No, other than newer ones that support Power Nap, a Mac does nothing during sleep. Never did.
It may dream though.
John Galt wrote:
It may dream though.
Now, there is a metaphysical thought to sleep on! 😎
As the others have said, no, a Mac does not run any kind of diagnostics while it sleeps. For that matter, it really doesn't run anything that I would call "diagnostics" on an automated basis at all. I think you may be confusing this with the periodic maintenance scripts that mende1 mentioned.
Basically, when it comes to such things, don't worry about it. Your Mac is pretty good at taking care of itself. If you're having problems of some kind, let us know what those are so we can help you fix them.
.. finally, someone with intellect and humor on this board!
.. but it you leave it on at night, the OS will run the Unix CRON maintrenance routines.. during 3:15 and 5:30am (not in Sleep mode), the cron tasks will be run.
That's what the link mende1 posted refers to. Note that those routine run when the machine wakes up, if it was sleeping at the normal run time. Also note that those scripts are extremely unimportant these days.
You can check when they have run by launching Terminal and at the prompt copy & paste
ls -al /var/log/*.out
Then press return.
Those scripts are an ancient carry over from UNIX. They were originally written for large Unix servers, running 24/7 and they were set to run in the wee hours because that's when the servers were least busy. I've never heard of a Mac going down due to bloated periodics but it's nice to know those caches are kept clean 😉
Russa wrote:
.. but it you leave it on at night, the OS will run the Unix CRON maintrenance routines.. during 3:15 and 5:30am (not in Sleep mode), the cron tasks will be run.
Russa, from the KB article you linked notice that those maintenance scripts are no longer invoked by cron. They are invoked by launchd:
Additional Information
The tasks are scheduled for 03:15 to 05:30 in your computer's local time zone. This is described further in "Mac OS X: Unexplained Disk Activity Produced by 'find' Process." These tasks do not run if the computer is shut down or in sleep mode. If the tasks do not run, it is possible that certain log files (such as system.log) may become very large in Mac OS X v10.5 or earlier.
Therefore no user intervention is required, unless you are running Mac OS X "Leopard" or earlier.
It may seem overly pedantic to bring this up but this common misconception has a tendency to lead people into believing a Mac requires the user to perform maintenance over and beyond what OS X already accomplishes by default.
As others have written, a Mac takes care of its own housekeeping. It is best to simply let it work as designed.
John Galt wrote:
those maintenance scripts are no longer invoked by cron. They are invoked by launchd:
Not for a long time, in 10.4 the scripts were changed from crontab to launchd.
.. accuracy is important.. I guess I even contradicted myself by saying the CRON scripts are run automatically! I know they're run at night automatically, just wrong on the routine executed. 🙂
Thomas A Reed wrote:
For that matter, it really doesn't run anything that I would call "diagnostics" on an automated basis at all.
I wonder if the OS performs any diagnostics at startup/restart/login.
drdocument wrote:
Thomas A Reed wrote:
For that matter, it really doesn't run anything that I would call "diagnostics" on an automated basis at all.
I wonder if the OS performs any diagnostics at startup/restart/login
To my knowledge the only diagnostics that happen are those at startup. That's what the startup chime is all about. When a Mac is started, restarted, or powered up the hardware performs a quick self-diagnostic check. If all is well the chime is sounded. If something isn't right the chime will consist of a series of tones that will tell the technician what the basic problem is. There have even been Easter eggs found in the diagnostic routines. My first Mac, the Power Mac 8100, had one. I forget the sequence of keys but the result was screeching tires followed by a loud automobile crash instead of the startup chime.
Of course when you start up in safe mode (holding down the shift key while booting) there are indeed diagnostic routines run, including some caches being clean/emptied.
I wonder if the OS performs any diagnostics at startup/restart/login.
Only the startup self-check that lkrupp mentioned.
does a mac perform self diagnostics during sleep mode?