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Thread: Debugging Kernel Panics - but /var/crash empty

  1. #1
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    Debugging Kernel Panics - but /var/crash empty

    I am currently running Ubuntu 12.10.
    Both in 12.04, and 12.10, I have been noticing random Kernel Panics that seem to happen only when I am not using the laptop.

    I went to follow the guide for getting the crash dump, but after a simulated crash (using sysreq c), /var/crash is empty. It is also empty after one of those random Kernel Panics.

    I have confirmed that crashdump has been added to my grub, and loaded (dmesg)

    cat /proc/cmdline
    Code:
    BOOT_IMAGE=/vmlinuz-3.5.0-25-generic root=UUID=f84dd846-ad9e-4b58-93dc-8d48020f9089 ro rootflags=subvol=@ crashkernel=384M-2G:64M,2G-:128M quiet splash acpi_osi= vt.handoff=7
    dmesg -i | grep crash
    Code:
    [    0.000000] Command line: BOOT_IMAGE=/vmlinuz-3.5.0-25-generic root=UUID=f84dd846-ad9e-4b58-93dc-8d48020f9089 ro rootflags=subvol=@ crashkernel=384M-2G:64M,2G-:128M quiet splash acpi_osi= vt.handoff=7
    [    0.000000] Reserving 128MB of memory at 720MB for crashkernel (System RAM: 5995MB)
    [    0.000000] Kernel command line: BOOT_IMAGE=/vmlinuz-3.5.0-25-generic root=UUID=f84dd846-ad9e-4b58-93dc-8d48020f9089 ro rootflags=subvol=@ crashkernel=384M-2G:64M,2G-:128M quiet splash acpi_osi= vt.handoff=7
    EDIT: it now appears that kexec/kdump is not loading after the crash - system is not restarting


    Any ideas?
    Last edited by sandyd; March 22nd, 2013 at 06:27 PM.

  2. #2
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    Re: Debugging Kernel Panics - but /var/crash empty

    I can't help on your question, but: did you run memtest86 to rule out memory problems?

  3. #3
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    Re: Debugging Kernel Panics - but /var/crash empty

    What is the hardware? Possible power supply issue? How old is the hardware?

    Linux is very good at capturing errors when they are truly software-generated. Not so good at hardware errors--intermittent disk, bad RAM, wonky power supply. The fact that the panics are happening during idle periods also points to hardware, as there are fewer processes running to contribute to a crash. And, you have experienced the issue with both 12.04 and 12.10. You can possibly rule out the hard disk by running a Live DVD session, and see how much uptime you get before a crash. That would rule out the hard disk. If it runs for several days without issue on the Live DVD, then you can start to look at the disk.

    What are the SMART parameters of the disk drive?
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  4. #4
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    Re: Debugging Kernel Panics - but /var/crash empty

    Hi sandyd

    Do you have
    Code:
    /proc/vmcore
    ?

    That's what it's dumping to the file.

    Take a look at

    Code:
    /usr/share/initramfs-tools/scripts/init-bottom/0_kdump
    Code:
    KVER="`uname -r`"
    CRASHFILE="/var/crash/vmcore"
    MAKEDUMPFILE="/usr/bin/makedumpfile"
    LOG="$rootmnt/var/crash/vmcore.log"
    VMCORE="/proc/vmcore"
    
    <snip>
    
    chroot $rootmnt $MAKEDUMPFILE -E -d 31 $VMCORE $CRASHFILE > $LOG 2>&1
    Also have a read of this

    https://bugs.launchpad.net/ubuntu/+s...ux/+bug/710733

    I think that documentation is hopelessly out of date. Surley one should not have to compile a kernel just to get /proc/vmcore support ?

    Still, you're doing better than i am.

    Code:
    matthew-S206:/home/matthew % cat /sys/kernel/{kexec_loaded,kexec_crash_loaded}
    0
    0
    matthew-S206:/home/matthew %
    I'm not using a debug kernel, only a Ubuntu kernel from the ppa.
    Code:
    matthew-S206:/home/matthew % uname -r
    3.9.0-030900rc3-generic
    matthew-S206:/home/matthew %
    Kind regards
    Last edited by matt_symes; March 22nd, 2013 at 11:48 PM.
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  5. #5
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    Re: Debugging Kernel Panics - but /var/crash empty

    Quote Originally Posted by sanderj View Post
    I can't help on your question, but: did you run memtest86 to rule out memory problems?
    yep

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    Re: Debugging Kernel Panics - but /var/crash empty

    Quote Originally Posted by matt_symes View Post
    Hi sandyd

    Do you have
    Code:
    /proc/vmcore
    ?

    That's what it's dumping to the file.

    Take a look at

    Code:
    /usr/share/initramfs-tools/scripts/init-bottom/0_kdump
    Code:
    KVER="`uname -r`"
    CRASHFILE="/var/crash/vmcore"
    MAKEDUMPFILE="/usr/bin/makedumpfile"
    LOG="$rootmnt/var/crash/vmcore.log"
    VMCORE="/proc/vmcore"
    
    <snip>
    
    chroot $rootmnt $MAKEDUMPFILE -E -d 31 $VMCORE $CRASHFILE > $LOG 2>&1
    Also have a read of this

    https://bugs.launchpad.net/ubuntu/+s...ux/+bug/710733

    I think that documentation is hopelessly out of date. Surley one should not have to compile a kernel just to get /proc/vmcore support ?

    Still, you're doing better than i am.

    Code:
    matthew-S206:/home/matthew % cat /sys/kernel/{kexec_loaded,kexec_crash_loaded}
    0
    0
    matthew-S206:/home/matthew %
    I'm not using a debug kernel, only a Ubuntu kernel from the ppa.
    Code:
    matthew-S206:/home/matthew % uname -r
    3.9.0-030900rc3-generic
    matthew-S206:/home/matthew %
    Kind regards
    I am missing a /proc/vmcore as well, but...
    Code:
     cat /sys/kernel/{kexec_loaded,kexec_crash_loaded}
    0
    1

  7. #7
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    Re: Debugging Kernel Panics - but /var/crash empty

    Hi

    Code:
    cat /sys/kernel/{kexec_loaded,kexec_crash_loaded} 
    0 
    1
    You're using a debug kernel ? You compiled it yourself ?
    Code:
    matthew-S206:/boot/grub % cat /etc/default/kexec 
    # Defaults for kexec initscript
    # sourced by /etc/init.d/kexec and /etc/init.d/kexec-load
    
    # Load a kexec kernel (true/false)
    LOAD_KEXEC=true
    
    # Kernel and initrd image
    KERNEL_IMAGE="/vmlinuz"
    INITRD="/initrd.img"
    
    # If empty, use current /proc/cmdline
    APPEND=""
    
    # Load the default kernel from grub config (true/false)
    USE_GRUB_CONFIG=true
    matthew-S206:/boot/grub %
    Is yours the same ?

    Kind regards
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  8. #8
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    Re: Debugging Kernel Panics - but /var/crash empty

    Quote Originally Posted by matt_symes View Post
    Hi

    Code:
    cat /sys/kernel/{kexec_loaded,kexec_crash_loaded} 
    0 
    1
    You're using a debug kernel ? You compiled it yourself ?
    Code:
    matthew-S206:/boot/grub % cat /etc/default/kexec 
    # Defaults for kexec initscript
    # sourced by /etc/init.d/kexec and /etc/init.d/kexec-load
    
    # Load a kexec kernel (true/false)
    LOAD_KEXEC=true
    
    # Kernel and initrd image
    KERNEL_IMAGE="/vmlinuz"
    INITRD="/initrd.img"
    
    # If empty, use current /proc/cmdline
    APPEND=""
    
    # Load the default kernel from grub config (true/false)
    USE_GRUB_CONFIG=true
    matthew-S206:/boot/grub %
    Is yours the same ?

    Kind regards
    Im using the debug kernels from http://ddebs.ubuntu.com/pool/main/l/linux/

    the config is the same

  9. #9
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    Re: Debugging Kernel Panics - but /var/crash empty

    Thanks sandyd. I'll be having a play over the weekend.
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