| View previous topic :: View next topic |
| Author |
Message |
ckoeber
Apprentice
Joined: 21 May 2007
Posts: 156
|
 Posted: Fri May 17, 2013 1:10 am Post subject: Dealing with Kernel Panics when you can't see the error ... |
 |
|
[SOLVED]
Hello,
I have a rather simple problem that I can't seem to find an answer for with Google; I am installing Gentoo (Kernel 3.8.13 on x86_64) and after the reboot I get a kernel panic.
The problem is I get the Call Trace and it gives me a bunch of text which doesn't allow me to see what the actual problem was.
Is there an option I can enable, at least temporarily, to remove the call trace to see the error message?
Or, in general, how can I find the actual problem of why I am getting a panic message?
Thank you for your time.
Last edited by ckoeber on Tue May 21, 2013 6:32 pm; edited 1 time in total |
|
| Back to top |
|
 |
BradN
Advocate
Joined: 19 Apr 2002
Posts: 2391
Location: Wisconsin (USA)
|
| Posted: Fri May 17, 2013 5:56 am Post subject: |
|
|
Look into using console over network or serial port, is the best suggestion I can think of.
Failing that, is your kernel custom configured? If so, consider using a genkernel config or livecd config as a basis and then modify from there. Probably you will miss the option that is causing it to crash (or else, if you know it's not crashing with the defaults you can narrow it down at least!)
Good luck! |
|
| Back to top |
|
|
Hu
Moderator
Joined: 06 Mar 2007
Posts: 21630
|
| Posted: Sat May 18, 2013 12:43 am Post subject: |
|
|
| If you use the framebuffer console, the increased resolution may give you enough extra lines on screen to see the error message. |
|
| Back to top |
|
|
DONAHUE
Watchman
Joined: 09 Dec 2006
Posts: 7651
Location: Goose Creek SC
|
| Posted: Sat May 18, 2013 3:28 am Post subject: |
|
|
phone or digcam that does movies, record the boot, playback in slow motion or frame by frame.
_________________
Defund the FCC. |
|
| Back to top |
|
|
krinn
Watchman
Joined: 02 May 2003
Posts: 7470
|
| Posted: Sat May 18, 2013 4:20 pm Post subject: |
|
|
| it will also get record in dmesg, something that will of course get clean on next boot, so you need to access it without booting it, something easy to do with any livecd. |
|
| Back to top |
|
|
[n00b@localhost]
Apprentice
Joined: 30 Aug 2004
Posts: 266
Location: London, UK
|
| Posted: Sat May 18, 2013 4:24 pm Post subject: |
|
|
| The output from dmesg gets logged to /var/log/dmesg.log which you can read using a liveCD. |
|
| Back to top |
|
|
Jaglover
Watchman
Joined: 29 May 2005
Posts: 8291
Location: Saint Amant, Acadiana
|
|
| Back to top |
|
|
Hu
Moderator
Joined: 06 Mar 2007
Posts: 21630
|
| Posted: Sat May 18, 2013 4:42 pm Post subject: |
|
|
Assuming the OP is correct to call his event a kernel panic, then nothing will be written to the filesystem, so there is no way to retrieve it from /var/log/dmesg.log. Similarly, once the kernel panics, you cannot scroll back.
Some new users mistakenly call any BUG or OOPS event a kernel panic. However, since the OP says this happens right after reboot and says he is installing Gentoo, the odds are good that he is correct to call it a kernel panic and that the problem is some sort of kernel configuration problem that results in a failure to start init. |
|
| Back to top |
|
|
BradN
Advocate
Joined: 19 Apr 2002
Posts: 2391
Location: Wisconsin (USA)
|
| Posted: Sat May 18, 2013 6:50 pm Post subject: |
|
|
| Hu is right, in addition sometimes BUG/OOPS is followed immediately by something related that locks up the machine, so even in those cases it may not be possible to scroll the screen or retrieve from log files. |
|
| Back to top |
|
|
ckoeber
Apprentice
Joined: 21 May 2007
Posts: 156
|
| Posted: Tue May 21, 2013 5:23 pm Post subject: |
|
|
| Jaglover wrote: | | Did you try Shift+PgUp. |
Just tried this, doesn't work 
Thanks! |
|
| Back to top |
|
|
ckoeber
Apprentice
Joined: 21 May 2007
Posts: 156
|
| Posted: Tue May 21, 2013 5:25 pm Post subject: |
|
|
| BradN wrote: | Look into using console over network or serial port, is the best suggestion I can think of.
Failing that, is your kernel custom configured? If so, consider using a genkernel config or livecd config as a basis and then modify from there. Probably you will miss the option that is causing it to crash (or else, if you know it's not crashing with the defaults you can narrow it down at least!)
Good luck! |
I tried to get this to work but I always get the quick message (after a long pause) that the link was not ready (despite the network card being functional + everything working in the LiveCD).
So, I will try the genkernel for now (I really like the manual config, faster bot times...) |
|
| Back to top |
|
|
ckoeber
Apprentice
Joined: 21 May 2007
Posts: 156
|
| Posted: Tue May 21, 2013 5:35 pm Post subject: |
|
|
| Hu wrote: | Assuming the OP is correct to call his event a kernel panic, then nothing will be written to the filesystem, so there is no way to retrieve it from /var/log/dmesg.log. Similarly, once the kernel panics, you cannot scroll back.
Some new users mistakenly call any BUG or OOPS event a kernel panic. However, since the OP says this happens right after reboot and says he is installing Gentoo, the odds are good that he is correct to call it a kernel panic and that the problem is some sort of kernel configuration problem that results in a failure to start init. |
I see, what I DID find is that I can add a loglevel option to change the output from the boot system.
A little better output can be obtained:
| Code: | loglevel= All Kernel Messages with a loglevel smaller than the
console loglevel will be printed to the console. It can
also be changed with klogd or other programs. The
loglevels are defined as follows:
0 (KERN_EMERG) system is unusable
1 (KERN_ALERT) action must be taken immediately
2 (KERN_CRIT) critical conditions
3 (KERN_ERR) error conditions
4 (KERN_WARNING) warning conditions
5 (KERN_NOTICE) normal but significant condition
6 (KERN_INFO) informational
7 (KERN_DEBUG) debug-level messages |
Also, this is helpful:
| Code: | logo.nologo [FB] Disables display of the built-in Linux logo.
This may be used to provide more screen space for
kernel log messages and is useful when debugging
kernel boot problems. |
So I answered my own question, in a way. I'll mark this thread as solved (and start a new thread possibly shortly) |
|
| Back to top |
|
|
TomWij
Retired Dev
Joined: 04 Jul 2012
Posts: 1553
|
| Posted: Tue May 21, 2013 8:13 pm Post subject: |
|
|
| Code: | boot_delay= Milliseconds to delay each printk during boot.
Values larger than (10000) are changed to
no delay (0).
Format: integer |
|
|
| Back to top |
|
|
|
Installing Gentoo
