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    Subjectcan I bring Linux down by running "renice -20 cpu_intensive_process"?
    I have a Linux server (kernel 2.6.8.1 + Linux RAID1) which is a "backup" 
    machine: it gets the files from other servers, compresses it, writes to
    the tape, checks md5sums etc.

    It's been running for quite a bit, no problems with stability so far.

    Yesterday, something happened though.

    I was logged in remotely, and the system was running md5sum against a 30
    GB file.

    I wanted the things to speed up a bit, and made "renice -20 <md5sum_pid>".

    Few minutes after that I couldn't start any process, so I thought I made
    the system so busy with renice -20, that my SSH session probably
    disconnected.

    In the morning, the system was still unavailable - I could ping it, I
    could telnet to any of the ports opened, but nothing more happened.

    SSH was waiting forever after:

    debug1: identity file /root/.ssh/identity type -1
    debug1: identity file /root/.ssh/id_rsa type -1
    debug1: identity file /root/.ssh/id_dsa type -1


    Nothing was displayed on the monitor (all black).

    As I restarted the machine, I saw that the logging ends few minutes
    after I changed the priority of md5sum to -20.


    So here is my question: is it possible to bring down the machine by
    simply doing "renice -20 cpu_intensive_process"?

    As I said, this machine does heavy compression and md5sum calculations
    of big files every day, and was stable all the time - but stopped
    responding after I changed the priority of a CPU-intensive process to -20.

    Coincidence and a hardware failure?

    --
    Tomasz Chmielewski
    http://wpkg.org
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