# iMac (x86) spontaneously reboots

## wdreinhart

I have a iMac 4,1 (2006, first generation of Intel architecture Macs) that has started rebooting spontaneously.

Things known (or at least suspected) so far:

The reboots began after switching from the generic desktop profile to desktop/kde

If there are any helpful log entries, they're lost before being written to disk.  /var/log/messages has normal operating logs before a reboot, then normal boot messages afterward.

It seems like the reboot happens right after a display mode change: screen on/off, starting/stopping X, playing games, etc.

I'm using the new radeon (kms) kernel and xorg drivers, not fglrx.

The machine was running kernel 3.8.8 when I first encountered the reboots, I've tested 3.9.0 and back as far as 3.8.4, and they still happen.

It's not caused by a kernel panic, I have /proc/sys/kernel/panic set to 0, so no rebooting after a panic.

My memtest86 disc won't boot thanks to Apple's insanely great ( :Rolling Eyes: ) EFI implementation.

Any ideas?  It's driving me crazy!

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## ulenrich

There is only special to profile kde/use.force

consolekit

policykit

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## Ant P.

Check your hardware sensors - iMacs are infamous for poor build quality (far too much thermal paste) causing CPUs to overheat past their hardware thresholds.

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## wdreinhart

Hmmm, the CPU temp is getting up to 62C in the middle of emerging LibreOffice.  Intel docs say it should be OK up to 100, but that sounds very hot to me.  I'll bump the minimum fan speeds up and see if it helps.

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## Ant P.

62°C under load sounds perfectly reasonable - that's probably not the cause then.

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## Voltago

If you can get hold of two usb-to-serial adapters and a null-modem cable, you could build yourself a serial console viewable from another machine, and hope that the error message still gets transmitted (if not, chances are your hardware is broken anyways I'd say...). Or another way (which I'm not sure will work though): Mount /var/log on a non-system drive (maybe a reasonably fast usb key might work) with mount-option 'sync', again hoping that the write operation will complete before the system goes down.

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## Hu

If a second system is available, using netconsole is probably easier than trying to create a serial console on a machine that lacks serial.

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## Voltago

 *Hu wrote:*   

> If a second system is available, using netconsole is probably easier than trying to create a serial console on a machine that lacks serial.

 

There is a netconsole nowadays? Truly, this is the future! (Coming to think of it, it probably has been around for a long time)

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## wdreinhart

 *Hu wrote:*   

> If a second system is available, using netconsole is probably easier than trying to create a serial console on a machine that lacks serial.

 

Definitely easier, since the only machine I have with serial ports is headless.  I'll build a kernel with netconsole tonight and see what it captures.

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