Lessons from power glitch and outage

Mon Oct 24 23:01:07 EDT 2016

I've had problems with doing unclean shutdowns on this Hackintosh because,
due to having OS X on a tiny SSD drive, I have my home directory symlinked
to another volume on the hard disk.
/Users->/Volumes/Users
The problem being that you can't hard code what name the volume gets when
it auto-mounts.
So occasionally Volumes/Users mounts /Users as Users1, Users2, ...Users5
 and I end up with an empty home directory until I jump though
eleventy-seven reboot hoops to update the symlink.
That mess only happens when I'm forced to hit the power switch repeatedly
when it locks up.
I know. That's what I get...

(I just built a screaming Hackintosh tower that's in a Power Mac class.)

--Mike

On Mon, Oct 24, 2016 at 7:12 PM, Tom Yarmas <tom at yarmas.com> wrote:

> Corruption risk from an unclean shutdown? I think that’s just old school
> thinking. OS X has had journaling of HFS volumes on by default since like
> 2002, I think. Windows was probably the last time you really risked file
> system corruption from an unclean shutdown. Have anyone lost data recently
> due to an unclean shutdown? I know I think nothing of power cycling my many
> Macs during a hang or other problem.
>
> Just don’t see how the Mac is supposed to know to power back on once the
> power comes back if you shutdown the system properly???
>
> -tom
>
>
> On Oct 24, 2016, at 6:36 PM, Mike Andrews <mikea0 at gmail.com> wrote:
>
> That's Microsoft-worthy stupidity - either risk corruption from an unclean
> shutdown or have it not come cak when power is restored.
> Is there a way to power up a Mac externally, like with Wake-on-LAN?
>
> --Mike
>
>
> On Mon, Oct 24, 2016 at 1:08 PM, Kurt Sheffer <ksheffer at mindspring.com>
> wrote:
>
>> The Mac definitely won’t turn itself back on after a clean shutdown.
>> Nothing has changed in that regard. I’m hesitant to pull the plug to test
>> it the other way.
>>
>> I had to unplug my UPS from USB recently because of a strange problem.
>> When the UPS kicks in due to a voltage dip (a frequent event here), the
>> entire Mac OS GUI will freeze up and become unresponsive. XTension also
>> stops processing events— it’s like time has stopped. I can still SSH in and
>> do a "shutdown -r now” but I can't get logged in even with a physical
>> keyboard and monitor. It doesn’t happen every time of course. That would be
>> too easy. Now I’ve disconnected the USB interface and we’ll see if it’s a
>> software problem, or something related to the quality of the power provided
>> by the UPS.
>>
>> -Kurt
>>
>> On Oct 19, 2016, at 8:59 AM, James Sentman <james at sentman.com> wrote:
>>
>> Our power was off for several days with Hurricane Matthew. (the house was
>> absolutely fine though many neighbors were not so lucky, all our trees feel
>> away from the house! It will be some time before the yard and all those
>> trees are cleared up) I THOUGHT I had everything setup. I expected XTension
>> to be running when I arrived back home after our evacuation but it was not!
>> I had the restart after a power failure turned on, yet the mini did not
>> restart.
>>
>> You don’t need to install any software for the UPS, OSX supports all
>> those things automatically. Just plug it in and it will show up as if the
>> mac had a battery like a macbook. You can then set the regular settings in
>> the energy saver control panel like usual.
>>
>> unfortunately what you don’t want to do is to have it shut down cleanly.
>> If you do a clean shutdown then the “restart after a power failure” doesn’t
>> work. Or at least it didn’t work I will have to revisit these things since
>> they aren’t working the way I thought they did anymore.
>>
>> What you can do is as soon as the power goes out you can tell XTension to
>> write it’s database to disk, and then you can do a sync on the file systems
>> so that the disks are less likely to be corrupt if power is lost. The
>> journaling should keep them OK anyway, but I still do this. If you setup
>> the UPS interface in XTension you can create a unit for the AC power and
>> when it turns off you can do a:
>>
>>
>> save database
>> do shell script “sync”
>>
>> the sync makes sure that all the caches have been written to disk. Then
>> if the power does fail you won’t lose anything. You might do something
>> clever with the time left unit on the UPS and do this closer to the time
>> that it will actually shut you off, but make sure you’re not doing it
>> constantly after a certain time or something. I would actually create a
>> scheduled event to run a global script in say a minute. In the global
>> script I would check to see if the power is still off and the time left
>> unit is less than say 10 minutes and if so I would do the save and the sync
>> and then exit. If the power was on I would just exit.  If the power was
>> still off and the time left was more than 10 minutes I would do an execute
>> script (thisScript) in 1 * minutes so that it will keep checking until
>> either the power comes back on or until the time left runs down to the
>> point of doing the task.
>>
>> We may all want to revisit our power failure logic as mine just isn’t
>> doing what I thought it was doing anymore. I will post again about it when
>> I’ve figured out why my mini didn’t restart with the power.
>>
>> On Oct 18, 2016, at 7:54 PM, Mike Andrews <mikea0 at gmail.com> wrote:
>>
>> Set the option on the Mac server to power up when power is restored.
>> Put in UPS monitoring to get a clean shutdown for good measure
>>
>>
>> Thanks,
>>  James
>>
>>
>> James Sentman                       http://www.PlanetaryGear.org
>> <http://www.planetarygear.org/> http://MacHomeAutomation.com
>> <http://machomeautomation.com/>
>>
>>
>>
>>
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