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    SubjectRe: [RFC PATCH] cmdline: Hide "debug" from /proc/cmdline
    On 04/03/2014 10:05 AM, Theodore Ts'o wrote:
    > On Thu, Apr 03, 2014 at 12:43:08PM +0200, Joerg Roedel wrote:
    >>
    >> How about just ignoring writes to /dev/kmsg altogether by default
    >> (unless explicitly enabled in Kconfig or on the kernel cmdline)? Maybe I
    >> am missing something but what are the legitimate use-cases for generally
    >> allowing user-space to write into the kernel-log?
    >
    > I'll give you one example which where /dev/kmesg is useful --- if you
    > are running automated kernel tests, echoing "running test shared/127"
    > .... several minutes later .... "running test shared/128", is very
    > useful since if the kernel starts spewing warnings, or even
    > oops/panics/livelocks, you know what test was running at the time of
    > the failure.

    I'm using /dev/kmsg in virtme so that I can easily capture, with
    timestamps, the ten or so log lines that it produces. It would be sad
    if I had to worry about small ratelimits here.

    /dev/kmsg is genuinely useful for the case where an initramfs wants to
    log something (preferably only a little bit) and doesn't want to invent
    a whole protocol for passing logging data through to the final logging
    system.

    The other thing I've used /dev/kmsg for is to shove a "I'm starting
    something now" message in. This is only really necessary because the
    current kernel log timestamps are unusable crap. (We could fix that,
    hint hint.)

    --Andy


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