Can a mac reboot on its own after brief power failure?

[shellylh]

I was trying to figure out if my power was out last night during the storm so I can figure out whether to throw away perishable foods.  I think my computer (imac) was on when I came home this morning (although I was tired so I certainly could have turned it on without thinking).  I don't have the "startup automatically after a power failure" checked in energy saver nor do I have a UPS. If I type "last" in terminal, it has a reboot at 4:37am this morning (I was not here at that time).  Also, the system log says

 

4:37:43 AM locationd: locationd was started after an unclean shutdown

 

So that seems to indicated that computer shut down and restarted on its own.  

 

I did a test.  I unplugged my imac for about a minute.  It didn't start up on its own.  When I did start it up (after I turned it on), it said the same thing as above.  

 

Could it be that there was a very brief power disruption/flicker that caused it to reboot on its own? 

Edited May 26, 2015 by shellylh

[shellylh]

I also found the following in the system.log files.  Does anyone know what the code 5 means?  

 

May 26 01:00:00 Shellys-iMac kernel[0]: Previous sleep cause: 5

May 26 02:48:47 Shellys-iMac kernel[0]: Previous sleep cause: 5

[grawk]

yes, a brief enough power outage could have triggered a panic.

I don't know what code 5 is tho.

[shellylh]

What does a "panic" mean? 

 

Would there be something in the system.log file when this happens?  

Edited May 26, 2015 by shellylh

[Hopstretch]

Shelly, mine used to do that in SA when we got power surges. Screen flicks off, WTF?, "Bong!", reboot.

 

No expert but think the logging you're seeing is just because there were processes that were running when it hard quit and it's going to note that those weren't properly shut down.

[grawk]

panic's just the official name for a system reboot due to error.

[shellylh]

Ok, so it might do a reboot instead of just turning off if there was a surge or very brief power interruption (although I do have a good surge protector).  I assume that if it is a long enough outage then it would just turn off. 

[Voltron]

My guess is that your power was not out but dipped enough that the Mac restarted.  They do not reboot after a long outage according to recent experience here.

[Grahame]

Shelly, are you running a computer without a UPS?

Is that a cost / benefit to you? - ability to ride out transient surges / brown outs , shut down safely / cleanly for longer outages , 

avoid disk failures on hard stops etc.

Can be inexpensive (e.g. < $60) http://www.amazon.com/APC-BE550G-Back-UPS-8-outlet-Uninterruptible/dp/B0019804U8/ref=sr_1_1?ie=UTF8&qid=1432677002&sr=8-1&keywords=UPS

 

How much uptime do you want?

[shellylh]

I hadn't really thought about one.   I have never lost work due to the computer suddenly shutting down because of a power outage but maybe I have been lucky.  Will your computer run better in the long term if you always shut down safely?  Can you use this with a surge protector.   I have a Zero Surge right now which I think is better than the surge in the APC.  I have been less than thrilled with some of my plastic APC surge protectors in the past especially because half the time I plug something in, it doesn't get power (poor connections).  Maybe this one is better. 

[HeadphoneAddict]

Ok, so it might do a reboot instead of just turning off if there was a surge or very brief power interruption (although I do have a good surge protector).  I assume that if it is a long enough outage then it would just turn off. 

 

Also run disk utility and verify your hard drive and any other drive that could have been used at the time it crashed/rebooted.  If you do it in recovery mode then you can also do a repair of the boot drive if there's an error.