MacOS Sierra on external drive – Mac do not go to sleep anymore

external-diskhard drivesleep-wakessdusb

Since two days I am using an external SSD as system disk (to work with my system on my iMac or on my new arriving MacBook Pro – on demand – without any synchronization process). Just attach the disk and boot my system.

On my iMac this work pretty good. I have tested my Thunderbold 2 case – wich was faster on boot as the USB 3.0 case. But the Thunderbold case need external power – so thats not perfect.

Now I am using the USB 3.0 case just connected via USB. And this morning I noticed, that my iMac didn't went to sleep – just the dispay turned off. So the system will not go to sleep automatically. After 5 minutes with turned off display I can still see some flashing LED on the SSD case – once a minute or something.

What can I do to get my system automatically to sleep again?

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Update:

Running pmset -g in Terminal, I get the following

Currently in use: 
standby               1 
Sleep On Power Button 1 
womp                  0 
halfdim               1 
hibernatefile         /var/vm/sleepimage 
powernap              0 
autorestart           0 
networkoversleep      0 
disksleep             0 
sleep                 1 (sleep prevented by backupd, backupd, UserEventAgent) 
autopoweroffdelay     28800 
hibernatemode         0 
autopoweroff          1 
ttyskeepawake         1 
displaysleep          1 
standbydelay          10800

Best Answer

It won't go to sleep because it can't.

There's a process (or processes) preventing your system from going to sleep. pmset -g tells us:

(sleep prevented by backupd, backupd, UserEventAgent)

  • backupd is the Time Machine backup daemon which more than likely is backing up to a USB drive.

  • UserEventAgent is a processes that manages high level events that launchd doesn't manage - this could be any number of things.

To put the machine to sleep you will need to disable Time Machine and resolve whatever process UserEventAgent is attached to (it may be Time Machine itself).

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