# How do I debug system freezes (Fedora 28)

I am running Fedora 28 on a Lenovo ThinkCenter using intel graphics, and for the past month or two it has been freezing randomly. I don't see a pattern; sometimes I'm in the middle of editing a document, sometimes I'm opening a new browser tab, and sometimes I'm not even present at the computer-- I just come back to it and it's hung. When this happens, the keyboard and mouse do not work at all, and my only choice is to hard reboot the machine.

I have seen various reports of this sort of thing is my web searches, and people seem to think it is driver related. Everyone's configuration seems to be a little different, and I don't see a definitive one-size-fits-all answer (and frankly, most of the questions go unanswered). I'd like to gather useful debugging info to pinpoint my particular problem so someone might be able to help. What should I do?

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Have you checked the system logs after you reboot? Are there any errors or segfaults listed within the logs? Which Lenovo ThinkCenter Model do you have? What graphics chipset comes with it? You need to provide a lot more information. This post is very vague.

( 2018-07-29 19:35:11 -0600 )edit

I know it's vague! That's why I asked what I should do to debug it. To answer your questions:

• Yes, I checked the logs but I did not see a cause. However, I am not sure if I would even know the problem if I saw it-- there are a lot of logs with a lot of data to sift through.
• It is a Lenovo ThinkCentre M900z
• Graphics: Intel® HD Graphics 530 (Skylake GT2)
( 2018-07-30 16:50:37 -0600 )edit

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I had several hard hangs on my Fedora 27 workstation recently. I had enabled the magic SysRq key but that did not allow me to do anything. I could only power cycle the system and there was nothing in the logs that indicated what could have caused the hangs. I did install some updates last week and one of them was PulseAudio and the update info suggested there were some fixes for recent regressions. I had been listening to Spotify or watching a video at the times that it happened. I did not dig any deeper into the changelogs for PulseAudio but I figured I would throw this out as a possible idea.

My system is a Dell E6420, Intel Core i5-2520M, 8GB RAM, integrated video. I have F27 workstation installed plus Cinnamon Desktop which I primarily use and was using each time the system hung.

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There are several simple means:

• The one I use all the time is opening a new virtual console, login and use top to see what the system is doing. One opens a virtual console with the keyboard sequence Ctrl+Alt+F2 (or F3, F4, F5, F6). Use Ctrl+Alt+F1 to see the gui, the default session.

• There is also use of the Magic SysRq Key:

To force a crashdump, use Alt+SysRq (then) c. (On laptops, the Fn key may be needed to access SysRq, so press Fn+Alt+SysRq then c.) Reboot and then use the crashdump analysis utility, which might well be automatically triggered upon reboot. See this for background information and this for configuring crashdump, alternatives for causing a crashdump, and methods to analyze it.

See this and employ the acronym R eboot E ven I f S ystem U tterly B roken. The first step (R) might be enough to see what the system log has recently captured.

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Thanks for the tips! My keyboard is non-responsive when this happens and I don't even have a SysRq key (thanks, Lenovo), so I am afraid I might not be able to perform these steps, but I will try.

( 2018-07-30 16:57:29 -0600 )edit

On a Lenovo (which is what I have), SysRq is not marked, but it is produced by Fn+PrtSc.

( 2018-08-01 09:25:01 -0600 )edit