Q: HELP! IMac freeze/restart issue, Apple was no help

Goggle Chrome Helper is a known culprit.

https://productforums.google.com/forum/#!topic/chrome/_PsSKFsDLeY

Also, the Goggle browser itself is constantly harvesting marketing information because that is Google's business model.

If that's not it, I'd do a clean install of OS X and test that. If it still restarts then it's not a software problem.

You can install onto an external disk to test.

How to reinstall OS X on your Mac - Apple Support

Follow steps for "Erase your drive and re-install OS X" except you won't be erasing on your internal, choose the external disk to install on.

1. This procedure is a diagnostic test. It changes nothing, for better or worse, and therefore will not, in itself, solve the problem. But with the aid of the test results, the solution may take a few minutes, instead of hours or days.

The test works on OS X 10.8 ("Mountain Lion") and later. I don't recommend running it on older versions of OS X. It will do no harm, but it won't do much good either.

Don't be put off by the complexity of these instructions. The procedure is easy to do right, but it's also easy to do wrong, so I've made the instructions very detailed. You do harder tasks with the computer all the time.

2. If you don't already have a current backup, please back up all data before doing anything else. The backup is necessary on general principle, not because of anything in the test procedure. Backup is always a must, and when you're having any kind of trouble with the computer, you may be at higher than usual risk of losing data, whether you follow these instructions or not.

There are ways to back up a computer that isn't fully functional. Ask if you need guidance.

3. Below are instructions to run a UNIX shell script, a type of program. As I wrote above, it changes nothing. It doesn't send or receive any data on the network. All it does is to generate a human-readable report on the state of the computer. That report goes nowhere unless you choose to share it. If you prefer, you can act on it yourself without disclosing the contents to me or anyone else.

You should be wondering whether you can believe me, and whether it's safe to run a program at the behest of a stranger. In general, no, it's not safe and I don't encourage it.

In this case, however, there are ways for you to decide whether the program is safe without having to trust me. First, you can read it. Unlike an application that you download and click to run, it's transparent, so anyone who understands the code can verify what it does.

You may not be able to understand the script yourself. But variations of it have been posted on this website many times over a period of years. Any one of the millions of registered users could have read the script and raised the alarm if it was harmful. Then I would not be here now and you would not be reading this message. See, for example, this discussion.

Nevertheless, if you can't satisfy yourself that these instructions are safe, don't follow them. Ask for other options.

4. Here's a general summary of what you need to do, if you choose to proceed:

☞ Copy the text of a particular web page (not this one) to the Clipboard.

☞ Paste into the window of another application.

☞ Wait for the test to run. It usually takes a few minutes.

☞ Paste the results, which will have been copied automatically, back into a reply on this page.

These are not specific instructions; just an overview. The details are in parts 7 and 8 of this comment. The sequence is: copy, paste, wait, paste again. You don't need to copy a second time.

5. Try to test under conditions that reproduce the problem, as far as possible. For example, if the computer is intermittently slow, run the test during a slowdown.

You may have started up in safe mode. If the system is now in safe mode and works well enough in normal mode to run the test, restart as usual before running it. If you can only test in safe mode, do that.

6. If you have more than one user, and only one user is affected by the problem,, and the affected user is not an administrator, then please run the test twice: once while logged in as the affected user, and once as an administrator. The results may be different. The user that is created automatically on a new computer when you start it for the first time is an administrator. If you can't log in as an administrator, test as the affected user. Most personal Macs have only one user, and in that case this section doesn’t apply. Don't log in as root.

7. Load this linked web page (on the website "Pastebin") in Safari. Press the key combination command-A to select all the text, then copy it to the Clipboard by pressing command-C.

8. Launch the built-in Terminal application in any one of the following ways:

☞ Enter the first few letters of its name ("Terminal") into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad and start typing the name.

Click anywhere in the Terminal window to activate it. Paste from the Clipboard into the window by pressing command-V, then press return. The text you pasted should vanish immediately.

9. If you're logged in as an administrator, you'll be prompted for your login password. Nothing will be displayed when you type it. You will not see the usual dots in place of typed characters. Make sure caps lock is off. Type carefully and then press return. You may get a one-time warning to be careful. If you make three failed attempts to enter the password, the test will run anyway, but it will produce less information. If you don't know the password, or if you prefer not to enter it, just press return three times at the password prompt. Again, the script will still run.

If the test is taking much longer than usual to run because the computer is very slow, you might be prompted for your password a second time. The authorization that you grant by entering it expires automatically after five minutes.

If you're not logged in as an administrator, you won't be prompted for a password. The test will still run. It just won't do anything that requires administrator privileges.

10. The test may take a few minutes to run, depending on how many files you have and the speed of the computer. A computer that's abnormally slow may take longer to run the test. While it's running, a series of lines will appear in the Terminal window like this:

    Test started

        Part 1 of 4 done at: … sec
        …
        Part 4 of 4 done at: … sec

    The test results are on the Clipboard.

    Please close this window.

The intervals between parts won't be exactly equal, but they give a rough indication of progress.

Wait for the final message "Please close this window" to appear—again, usually within a few minutes. If you don't see that message within about 30 minutes, the test probably won't complete in a reasonable time. In that case, press the key combination control-C or command-period to stop it. Then go to the next step. You'll have incomplete results, but still something.

In order to get results, the test must either be allowed to complete or else manually stopped as above. If you close the Terminal window while the test is still running, the partial results won't be saved.

11. When the test is complete, or if you stopped it manually, quit Terminal. The results will have been saved to the Clipboard automatically. They are not shown in the Terminal window. Please don't copy anything from there. All you have to do is start a reply to this comment and then paste by pressing command-V again.

At the top of the results, there will be a line that begins with the words "Start time." If you don't see that, but instead see a mass of gibberish, you didn't wait for the "close this window" message. Please wait for it and try again.

If any private information, such as your name or email address, appears in the results, anonymize it before posting. Usually that won't be necessary.

12. When you post the results, you might see an error message on the web page: "You have included content in your post that is not permitted," or "The message contains invalid characters." That's a bug in the software that runs this website. Please post the test results on Pastebin, then post a link here to the page you created.

If you have an account on Pastebin, please don't select Private from the Paste Exposure menu on the page, because then no one but you will be able to see it.

13. When you're done with the test, it's gone. There is nothing to uninstall or clean up.

14. This is a public forum, and others may give you advice based on the results of the test. They speak for themselves, not for me. The test itself is harmless, but whatever else you do may not be. For others who choose to run it, I don't recommend that you post the test results on this website unless I asked you to.

15. The linked UNIX shell script bears a notice of copyright. Readers of ASC may copy it for their own personal use. Neither the whole nor any part may be redistributed.

First, as I wrote earlier, you should not run the script unless you can satisfy yourself that it's safe. I suggested some ways to do that.

The code is public and the output is readable. Apart from that, I don't share information about what it does. No one but myself needs to know, since the output is meant to be used only by me. Those to whom I suggest running it only need to know what the script doesn't do.

It doesn’t directly create, delete, or modify any files. Running it will indirectly cause the operating system to leave slight traces in log files, and perhaps in some temporary files that will eventually be deleted or overwritten. Those events are all part of normal system operation and will happen anyway, whether you run the script or not.

The script doesn’t send or receive any data on the network.

The output is placed on the Clipboard on exit, where it will stay until the user overwrites it or logs out. Otherwise the script leaves no trace in memory after the Terminal window has been closed.

By virtue of all the above, merely running the script will not change the way the computer works at all, nor will it reveal anything that you don't choose to reveal.

As for "conditions that reproduce the problem," in this case you would run the test while using the computer as you usually do.

The reply from the self-proclaimed "stranger" is legit. Sometimes others will post with a different approach to the problem. Only you can to decide which advice to choose. It’s an unfortunate reality here in ASC Discussions.

Hello Jon,

I wrote a little diagnostic program to help show what might be causing these problems. Download EtreCheck from http://www.etrecheck.com, run it, and paste the results here. EtreCheck is perfectly safe to run, does not ask for your password to install, and is signed with my Apple Developer ID.

You aren't going to extract any meaningful information from the log files. There are only a couple of possible log file entries that have any real meaning. And I don't mean that in a general sort of way - I mean exactly two.

EtreCheck is an open source project (see https://github.com/etresoft/EtreCheck) and I designed it to be readable by anyone. It is frequently used here in Apple Support Communities so there are a number of people who know how to read and interpret it. However, trying to make it readable by end users is a challenge I'm still working on. All I can do is ask you not to read too much into any colours it might display. It is reports what it finds. The problem might be caused by the entries in green, not the ones in red.

Disclaimer: Although EtreCheck is free, there are other links on my site that could give me some form of compensation, financial or otherwise.

I'm curious to know why you think that app is any safer to use than the script I linked to earlier. Are you aware, for example, that the app phones home? Do you know what information it sends back to its developer?

This has been a problem for me as well. I took my iMac into the Apple Store and they were unable to find any problems, at least with the hardware. The only other suggestion offered was to do a complete reinstall of the OS. I have yet to try this. Sometimes the problem will occur when I'm not at the computer. I can hear it rebooting from another room. Sometimes it will go an entire week without this problem occurring.

Like you stated, there is nothing in the logs and no error messages waiting on the reboot. There are no heavy duty tasks running. Mail, Safari, Slack and that's usually about it. I have been unable to establish any other pattern of usage which would explain it. Hardware is stock from when I ordered my machine back in September last year. No third party USB devices are plugged into it.

It is a baffling problem.

As I told Jon, you can do a clean install onto an external disk to check.