System shuts off randomly when booting Ubuntu

Joseph Dalton

1/18/23, 11:54 AM

I have a C246 mainboard with a Xeon CPU and ECC RAM. Using Ubuntu 20.04, the system randomly shuts off completely, as if power was lost.

At first, I suspected a HW problem. I switched the PSU, I swapped the mainboard (same model) and I ran MemTest to check RAM. The problem can occur when using a USB device (installer) or when installed to a disk. I tried installing Windows and never observed a shutdown, even after using it for many hours and booting many, many times.

The shutdowns most frequently occur when selecting the boot entry in grub. Most of the time, it will shut down after the boot messages are toward the end right before switching to graphical mode.

But it can also happen hours after boot. I cannot force a shutdown by applying stress, it happens most of the time when I do something simple like type a command in the terminal and hit enter. The occurence is strange; it can happen multiple times in row when trying to boot or it can happen after many hours or after rebooting. But sometimes it it possible to boot many times without it occuring.

What could be the cause of this? How can I diagnose it? Other systems such as Windows and MemTest don't seem to have this problem. I observed the same problem on Ubuntu 18.04. The HW is server/WS HW and it should be fairly common, certainly other people would have noticed this problem?

0 + 0

boot

grub2

shutdown

18.04

20.04

matigo

1/18/23, 12:12 PM

There is not much to suggest here beyond looking for errors within the boot and system logs in `/var/log`

Joseph Dalton

1/18/23, 1:36 PM

I tried looking for logs. But I think the boot process is not logged, which is most interesting. And otherwise, there is too much. Can you suggest what I should look for? I can post more info, if you help me.

matigo

1/18/23, 2:12 PM

You will find that `/var/log/boot.log` is a repository of all information related to booting and any messages logged during startup. Anything that says `Error`, `Fail`, or `Warning` should be considered an avenue for investigation.

Joseph Dalton

1/19/23, 7:22 AM

`/var/log/boot.log` does not exist. I also noted that most shutdown I observe seem to occur before the filesystem is mounted. I filmed the boot messages on screen, there are no errors before it shuts off. Next I checked journalctl and noted that indeed, there logs only starts later in a subsequent successful boot.

Joseph Dalton

1/19/23, 7:25 AM

So the PC just turns off so early that there are no logs. I also tried to find other clues in the logs earlier, but it may as well be that no cause is ever logged. So how do you diagnose something like this? You have no logs and something happens that causes the system to shut off with no clue. And it is not hardware because Windows works? Or is it?

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