RHEL 5 : Crash Dump capturing for Red Hat Linux


I have started unixadminschool.com ( aka gurkulindia.com) in 2009 as my own personal reference blog, and later sometime i have realized that my leanings might be helpful for other unixadmins if I manage my knowledge-base in more user friendly format. And the result is today's' unixadminschool.com. You can connect me at - https://www.linkedin.com/in/unixadminschool/

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8 Responses

  1. bigga says:

    I’m not really very much of the on the web viewer to be honest your sites great, continue! I will do not delay- bookmark your site an extra chance later on. Cheers

  2. Yogesh Raheja says:

    @Bigga, Its an honor for our Team. Thanks you very much for your boosters and Welcome to Gurkulindia. 

  3. Selvyn says:

    Hi Yogesh,

    Good job with the Unix/Linux articles. However this one about crash dump seems a bit obsolete. I believe the current versions of RHEL use kdump/kexex for crash dump.


  4. Yogesh Raheja says:

    Hello Selvyn, yes that very true. The newer versions of RHEL have kdump and kexex for crash dumps. Thanks for pointing this.

  5. Vathinth Raj T says:

    I am bit confuse on this .
    I have enabled the option set kernel.sysrq = 1 in /etc/syctl.conf.
    When my server gets hang , How I will get the crash dump for analyze the issue???
    plz help me to understand.

  6. Ramdev says:

    Hi Vathinth, if you want to force the kernel dump when the system hung … you can use the following key sequence if you are using the regular AT keyboard and directly connected to linux console.


    Command key can be any of the following:

    m – dump information about memory allocation
    t – dump thread state information
    p – dump current CPU registers and flags
    c – intentionally crash the system (useful for forcing a disk or netdump)
    s – immediately sync all mounted filesystems
    u – immediately remount all filesystems read-only
    b – immediately reboot the machine
    o – immediately power off the machine (if configured and supported)
    f – start the Out Of Memory Killer (OOM)
    w – dumps tasks that are in uninterruptable (blocked) state

    >> in other case if you using a HP ILO you can force for a crash dump

    using the serial BREAK sequence i.e. Esc + Ctrl + b — which triggers the Magic SysRq event.

    • Vathinth Raj T says:

      HI Ramdev,

      Thanks for your response.

      After the giving the above mentioned combination of keys , where the dump will be stored?

      And also after changing the setting in /etc/sysctl.conf , Is the machine need reboot?

      Thanks in advance.
      Vathinth Raj T

      • Ramdev says:

        I believe …. It should be under /cores//….. And you to activate the new sysctl settings either you can reboot the machine or you can use the “sysctl -p” command without reboot..

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