Kubuntu reboots automatically at boot

[joneall]

What that means is, most times when I boot the system, it reaches the point where it should display the login box, but instead reboots.

I tried to check in /var/log/syslog. There were entries for yesterday, but the first one for today is for the reboot. dmsg is practically useless, as it contains no timestamps.

How do I find out what happened the first time?

I just notiece an odd thing:

cat /etc/issue
Ubuntu 14.04.1 LTS \n \l

$ lsb_release -a
LSB Version: core-2.0-amd64:core-2.0-noarch:core-3.0-amd64:core-3.0-noarch:core-3.1-amd64:core-3.1-noarch:core-3.2-amd64:core-3.2-noarch:core-4.0-amd64:core-4.0-noarch:core-4.1-amd64:core-4.1-noarch:security-4.0-amd64:security-4.0-noarch:security-4.1-amd64:security-4.1-noarch
Distributor ID: Ubuntu
Description: Ubuntu 14.04.1 LTS
Release: 14.04
Codename: trusty

BUT

$ uname -a
Linux jon-linux 3.15.0-031500rc8-generic #201406012235 SMP Mon Jun 2 02:36:11 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

For info,

$ l1 /boot/vml*
/boot/vmlinuz-3.13.0-24-generic
/boot/vmlinuz-3.13.0-32-generic
/boot/vmlinuz-3.15.0-031500rc8-generic

I boot the 3.13.

[millusions]

thats a tough one. could it be overheating?

can show you mine, its also 14.4:

marty@arakia:/boot$ cat /etc/issue
Ubuntu 14.04 LTS \n \l

marty@arakia:/boot$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 14.04 LTS
Release: 14.04
Codename: trusty

marty@arakia:/boot$ uname -a
Linux arakia 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:12 UTC 2014 i686 athlon i686 GNU/Linux

marty@arakia:/boot$ ls -l vml*
-rw------- 1 root root 5800496 May 3 10:40 vmlinuz-3.13.0-24-generic
-rw------- 1 root root 5820336 Jul 15 15:06 vmlinuz-3.13.0-32-generic
marty@arakia:/boot$

[joneall]

thats a tough one. could it be overheating?

I have psensor running and current temps are 40°C and 50°C.

Another curiousity is that psensor sometimes displays both cores and sometimes only Core 0.

[millusions]

i have a thought,

when it's starting and you see Kubuntu logo, press escape
and watch it carefully to see if there's any clues there.

was it just a one off thing or does it happen every time you boot?

i dont use psensors so not familar with it, just had a look at the webpage it looks like a front end to lm-sensors...

i think in this case you have to narrow it down to software or hardware first?

[joneall]

i have a thought,

when it's starting and you see Kubuntu logo, press escape
and watch it carefully to see if there's any clues there.

was it just a one off thing or does it happen every time you boot?

i dont use psensors so not familar with it, just had a look at the webpage it looks like a front end to lm-sensors...

i think in this case you have to narrow it down to software or hardware first?

Well, I already have "splash" on the grub command line, so I see the details of the boot process. But they go by very fast. I'll try photographing the screen.

It happens about one boot out of three, I think. I will start to keep some stats. Why does it always work with the reboot? What sort of condition would be corrected by a reboot?

Yes, psensor frontends lm-sensor, which must be the guilty party in missing one core.

Thanks for your suggestions.

[millusions]

ok, every third is good , better than every single time.
if thats the case, it should be in /var/log/syslog ? if it reboots note the time.
thats probably the best bet as to whats causing the reboot