leaving core creation on. umcore and "ulimit -c unlimited" and kernel panic grup.conf edit crashkernel= and chkconfig --level 3 kdump on

Posted on 2011-05-01
Last Modified: 2016-02-11
Why are, umcore and "ulimit -c unlimited" and kernel panic grup.conf edit "crashkernel=" and "chkconfig --level 3 kdump on:, not set by default

What are the side affects of leaving these enabled indefinitely?
Question by:Dooglave
    LVL 4

    Expert Comment

    In 64bit environment process size can reach pretty big numbers (many gigabytes). Dumping so much into core can make server unusable for substantial amount of time and can fill up your disk, so limiting core size could be a good precaution.
    LVL 6

    Author Comment

    So can a core file be any larger than the amount of physical memory in the system?  Does swap usage play a role in increasing the filesize?

    Also If understand correctly disk space is about the only drawback to leaving usermode and kernal panic core dump creation turned on. I guess if someone had a history of neglecting or not monitoring their servers we could create a cron job to notify a core dump file was present or even clean up all the old files and just preserve the latest.

    LVL 4

    Accepted Solution

    Yes coredump of process can be larger than physical RAM because process can use all types of virtual memory including swap.

    Kernel core dump is different story. Linux dumps into swap when panics then extracts core from the swap during next boot.
    But i don't know whats the state of it now. about 5 years ago when I was playing with kernel panic settings on SuSE SLES9 I could not force kernel to panic on raid driver failure. All config settings for panic were in place, driver experienced failure which made block device to be unusable then linux still would continue to work and would not panic leaving application in half-broken state. So i didn't bother enabling it anywhere else since it does not work as it suppose to.

    Maybe they cleaned it up now. FreeBSD used to have way better error handling.

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