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Is the 'Find My Mac' feature of iCloud supposed to work while the computer is sleeping? I use this feature to check on things every once in a while, as well as show the feature off to other people. Every time I show them though, it always lists the machine as being offline.

I ask too because a 'sleeping' mac does actually wake up every once in a while (in a very low level state), to basically check and update its mDNS/Bonjour config, as well as a few other minor things (I know specifically my iMac does this, I haven't looked on my MBA). I figured that if it was waking to at least check this stuff, it would also propagate to Find My Mac.

Final Update: So after switching around more network configs (and going just wifi), it actually worked worse - I couldn't wake the machine locally either (and this is with wake on network access checked). So I think its either something odd with my setup, or actual machine (I know already wifi is odd on it - I tried a defaults command to enable airdrop, and that didn't work either). My actual issue is due to the machine not being able to wake from sleep.

New Update: So, noticed a few things. Wifi was on, but not connected (nor should it be). I turned it off, and disabled the interface, and it still doesn't wake the computer up on the Ethernet adapter. I just now tested the opposite way, and it actually looked like it worked! Want to try again a bit later to make sure.

Update: I re-enabled Find My Mac, and verified that wake on LAN was active. While it did work earlier on, once the computer actually went to sleep (about an hour later), it never seemed to want to update, until I woke the machine. Is Find My Mac supposed to wake it anyways? Or would Find My Mac while sleeping never actually show its current location until the next wake? As a precaution, I restarted my Mac and Airport Extreme just recently. Also, could this be a port forwarding issue on my FiOS router?

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My solution for my "desk" Mac has always been to allow the display to sleep, but to set computer sleep to never. This allows Crashplan backups to "catch up", SuperDuper backups to run, remote access and Find My Mac. –  jaberg Mar 21 '12 at 13:36
    
I used to just let the display sleep, and may go back to that. Backblaze usually doesn't have too much to catch up on, and not many things change daily, so I usually let it sleep. –  jmlumpkin Mar 21 '12 at 23:29
    
It was intended as a suggestion, not an answer. As for my backups—it all depends on how many "rolls of film" have been dropped off at the Aperture lab. Most days I'm current but sometimes it takes a week to get back to that state. I'm monitoring this one hoping a better solution is revealed. –  jaberg Mar 22 '12 at 9:36
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6 Answers

up vote 3 down vote accepted

The problem is that that your iMac is not waking from sleep.

Several people have been affected by this and discussed this on discussions.apple.com in these two threads. Both threads have been opened recently and deal with the "Wake on network access" problem in Lion.

It's required for your Mac to wake up because it needs to build up a Wi-Fi connection. Your iMac disconnects from the Wi-Fi in sleep mode. But without a connection to a known Wi-Fi network, Find my Mac cannot locate your computer.

This is what the iCloud troubleshooting guide says:

Find My Mac can only locate your Mac if it is connected to an internet via a known Wi-Fi network. If your Mac is connected to the internet only by an ethernet cable, Find My Mac will not be able to locate your Mac.

Idea

Does your iMac support wake on Airport network access? Newer Macs can wake up on both Airport and Ethernet access. This is then called "wake on network access" instead of "wake on ethernet/airport access".

If you iMac supports waking on Airport access, disable your Ethernet port. Maybe this will force the iMac to stay connected to the Wi-Fi during sleep and the 'bug' will not occur then.

enter image description here

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Could another issue here be Wifi versus Ethernet? Is there some requirement for it to be on Wifi? The machine does wake up when i'm in the network and try to connect to it through Finder (and AFP mount), or Screen Sharing –  jmlumpkin Mar 22 '12 at 18:50
    
Actually, another thing to note is that SSH'ing into it also works, from the outside, but thats a port forward –  jmlumpkin Mar 22 '12 at 18:51
    
@jmlumpkin I would try to make the ethernet port inactive in the system preferences. This will force your iMac to stay connected to Wi-Fi during sleep, i assume. Maybe this 'bug' will not occur then. –  gentmatt Mar 22 '12 at 18:57
    
Wifi is actually turned off, I wonder if it wants it on. –  jmlumpkin Mar 22 '12 at 18:59
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So I just tried the other way, and it looked like it may have worked! If so, I am not sure that I want to use Wifi vs Ethernet just for this feature to work while asleep. But I will submit a radar to Apple about the issue. –  jmlumpkin Mar 23 '12 at 0:48
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If the Mac is sleeping there is no way for iCloud to locate it and it appears offline.

However, as you noted, you can enable Wake for network access in energy preferences for it to periodically wake and check the network allow remote wake up using and AirPort.

When the Mac connects to iCloud next time, your commands (locate, lock, wipe, message/alert) are sent to it.

enter image description here

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Thing is, it actually still does 'wake' even without that checked, just not fully. Also, im pretty sure I have that option checked, and it does not update to iCloud for Find My Mac. I know it wakes for Remote Desktop or mounting an AFP share. –  jmlumpkin Mar 21 '12 at 12:43
    
@gentmatt you updated while I was posting my comment. I don't remember seeing this, and I was pretty sure I had that option on. Will check when back at my Mac. –  jmlumpkin Mar 21 '12 at 12:45
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@jmlumpkin According to Apple docs: If you have a portable computer, selecting this option wakes your computer only if it’s plugged in and the display is open. –  Vlad Mar 21 '12 at 12:50
    
thanks for that. I need to check this, because the one I am more curious about is my iMac. Not in my iMac being stolen, but moreso in I thought I had this checked. –  jmlumpkin Mar 21 '12 at 12:51
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@bmike - still, I has to be waken up before locating and it requires a specific infrastructure for this. I know, the devil is in the details! –  Vlad Mar 21 '12 at 15:07
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Yes it both can and is supposed to work while your mac sleeps, but it's far from perfect in several instances.


Apple has designed the hardware and software to let this specific and many other sorts of network accesses succeed even when a mac is sleeping to save energy.

This system relies on your Airport base station to proxy the incoming requests and wake up the mac when it detects and inbound request to locate, screen share, print to a shared printer or otherwise connect to the mac. Your AirPort doesn't sleep and is there to poke the mac and wake it up.

The two best articles to read up on this are:

In a nutshell, the mac will warn you if you have not set up the hardware to allow the router to wake it up on demand. This is also called "wake on lan" WOL and uses the concept of a "magic packet" that is broadcast to identify the specific machine that is being requested to wake up. Once the mac is set to actually listen for a wake up signal, then it communicates to the router about all of the services that it should be woken up for. This means the mac will wake from spell periodically to check in with the router to re-register as needing to be awoken.

As you can see - there are several components, so this isn't 100% perfectly reliable - if the router reboots while the mac is asleep, you will be unable to wake the mac up until it reaches its next timed interval to wake up and reregister. Also, problem networks and/or hardware can cause this to be less reliable, but I have been very happy with this for the past three years in several sites where I have this turned on.

Now - for the stolen mac situation, this is less useful than Find My Mac on an iOS device. First, the Wake on Demand does not succeed when a portable mac is not plugged in to power or an external display when the lid is shut. Second, the mac could be outside of WiFi access and unreachable. Third, the router where your mac might be sleeping (at a coffee shop for example) might not be an AirPort device or have the equivalent sleep proxy service enabled or even present. In those cases, your mac can not be located while sleeping. Until a data connection is added to a sleeping mac - the iOS devices will be far ahead in locating due to their near constant connection with the network when they are not powered off.


And at long last, many of my macs lost their registration some time between enabling this in Lion and upgrading to 10.7.3. I think the change to the Recovery HD might have caused the service to be looking for the old image and I am now in the practice of testing this monthly for important macs and just deleting and re-creating the Find My Mac registration after each software update that changes the core OS. Not knowing why they drop off, I'm trying to compensate and keep the system working by extra manual labor.

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Good thing you pointed out: it's designed to work with AirPort as a sleep proxy and will not work with other routers/wireless access points. –  Vlad Mar 21 '12 at 15:02
    
Luckily all this is behind an Airport Extreme, so that helps. I also agree that something has messed with Find My Mac registration, I will be posting another question later on that. –  jmlumpkin Mar 21 '12 at 23:38
    
@bmike I also am very familiar with WOL. I used to use it a lot to wake a media center mac mini, and even started work on an iPhone app to send the Magic Packet. I didn't know about the registering part. But there also is a part of the Mac OS that does a low level wake (not screen, and somehow doesn't spin up disks either) to check mDNS and other stuff. I think though the issue I am seeing is totally separate. –  jmlumpkin Mar 21 '12 at 23:40
    
@bmike does one have to do any special setting on the Airport Extreme to enable WoL? –  jmlumpkin Mar 22 '12 at 17:12
    
It just works. I believe many of the updates lately improve it's reliability as it's gotten much better in the last year. The source code is open source, so presumably other vendors can adopt the sleep proxy functionality or inquiring minds can learn more by looking at the source. –  bmike Mar 22 '12 at 18:01
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Yes - In the image below it has found mine, even though it is sleeping and has been for the last 12 hours. (sorry planet) Although I caught the screen shot when it was updating the location, but the green dot shows that it was found on both the iPhone app and the iCloud.com web app.

enter image description here

enter image description here

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They should be the same thing, or are you saying that iCloud wont show its status, but the app will? –  jmlumpkin Mar 21 '12 at 13:03
    
Sorry, should have checked that. I have no problem locating the Mac while it is sleeping –  Graeme Hutchison Mar 21 '12 at 13:10
    
Ok, I also checked the app, and it showed not connected as well. –  jmlumpkin Mar 21 '12 at 13:16
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I had the same problem. For me, what was wrong was that Find my Mac (and Back to my Mac) were not working reliably with Lion's low power wake. I disabled low power wake (that is, it now wakes on LAN to full power mode) by adding "darkwake=0" under the Kernel Flags key in the /Library/Preferences/SystemConfiguration/com.apple.Boot.plist file:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
        <key>Kernel</key>
        <string>mach_kernel</string>
        <key>Kernel Flags</key>
        <string>darkwake=0</string>
</dict>
</plist>
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send to your iMac signal from "find my iphone". After that it will work properly. Sounds strange but it worked for me.

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