2 Replies Latest reply: Nov 29, 2010 7:37 AM by RobbieSnr
RobbieSnr Level 1 Level 1 (0 points)
I've got into the habit of hibernating my iMac when I want to shut it down, for example when I'm going to be away from it for some time. It was working fine, when I selected Sleep there was some indication that it was saving everything away to the hard disk and when this was completed I switched off the power.

The last week or so when I select Sleep the screen goes blank and I can't tell what is happening. I leave it for a bit then switch off the power. When I switch back on again sometimes I see it reading from the hard disk and at other times it boots up from scratch. I can't recall now exactly what I used to see when I chose Sleep but the screen certainly didn't suddenly go blank.

I had a look at the Hibernatemode setting using pmset -g and this was set to 5. I noticed from another posting that this setting should be either 1, 3 or 25 so I reset it to 25 but this made no difference. I see that in the folder used to set the state of my computer in hibernation there is a sleepimage file and also two swapfiles. I don't know what the swapfiles are for but I haven't touched them.

Can anyone tell me how I can get back to the situation where I have some indication that the computer is hibernating and not closing down when I go for Sleep?

iMac, Mac OS X (10.6.5)
  • Dave Barnes Level 4 Level 4 (2,975 points)
    1. Mac OS X machines do not "hibernate". Windows machines hibernate. And, yes I know that BSD uses the term hibernate. By the way, my iMac hibernatemode=0.

    2. Select sleep if you are going to use your machine again within a few days. It draws a tiny amount of electricity in this state. Sleep is similar to hibernate in that states are preserved.

    3. Select shutdown if you do not plan to use it for a week or more. Do not shutdown with the power button, but use the menu command. It will still draw a tiny amount of electricity. (If you are concerned about power surges, lightening strikes whilst it is shutdown, then unplug it from the mains.)

    4. The only time you should be touching the power button is too turn it on.

    5. I only shutdown my Mac once a year when I go on a long holiday. Otherwise, it sleeps.
  • RobbieSnr Level 1 Level 1 (0 points)
    Thanks for your reply.
    Dave Barnes wrote:
    1. Mac OS X machines do not "hibernate". Windows machines hibernate. And, yes I know that BSD uses the term hibernate. By the way, my iMac hibernatemode=0.


    I've seen this comment elsewhere and don't quite understand it. MacBooks do 'hibernate' but perhaps by Mac you're excluding the laptops? However my iMac will hibernate if I set hibernatemode to 5 or 25 so it is possible. As regards Windows machines not all hibernate - I had one once that didn't have this facility, and also one where hibernation mode would only work if this facility was turned on specially. Could there perhaps be a problem with the PMS if hibernation mode is used?
    2. Select sleep if you are going to use your machine again within a few days. It draws a tiny amount of electricity in this state. Sleep is similar to hibernate in that states are preserved.


    States are preserved but only if there is power. It's not so much the question of amount of electricity used but that of security. There is certainly some fire risk, however small, from any electrical appliance that is left on. I work from home and I do try and switch as many appliances as possible when they're not being used.
    3. Select shutdown if you do not plan to use it for a week or more. Do not shutdown with the power button, but use the menu command. It will still draw a tiny amount of electricity. (If you are concerned about power surges, lightening strikes whilst it is shutdown, then unplug it from the mains.)


    I use shutdown when I'm going away on holiday for a few days or more, as I won't be wanting to pick up exactly where I left off when I get back.
    4. The only time you should be touching the power button is too turn it on.


    That's what I do, using the shortcut keys, or the Apple menu, for Sleep to go into hibernation mode.