dmesg - print or control the kernel ring buffer


SYNOPSIS

       dmesg [ -c ] [ -n level ] [ -s bufsize ]


DESCRIPTION

       dmesg  is  used  to  examine  or  control  the kernel ring
       buffer.

       The program helps users to print  out  their  bootup  mes­
       sages.   Instead of copying the messages by hand, the user
       need only:
              dmesg > boot.messages
       and mail the boot.messages file to whoever can debug their
       problem.


OPTIONS

       -c     Clear the ring buffer contents after printing.

       -sbufsize
              Use  a  buffer  of size bufsize to query the kernel
              ring buffer.   This  is  16392  by  default.   (The
              default  kernel  syslog  buffer  size  was  4096 at
              first, 8192 since 1.3.54, 16384 since 2.1.113.)  If
              you  have  set  the kernel buffer to be larger than
              the default then this option can be  used  to  view
              the entire buffer.

       -nlevel
              Set  the level at which logging of messages is done
              to the console.  For example,  -n  1  prevents  all
              messages,  expect panic messages, from appearing on
              the console.  All  levels  of  messages  are  still
              written  to  /proc/kmsg, so syslogd(8) can still be
              used  to  control  exactly  where  kernel  messages
              appear.  When the -n option is used, dmesg will not
              print or clear the kernel ring buffer.

              When both options are used, only the last option on
              the command line will have an effect.


SEE ALSO

       syslogd(8)


AUTHOR

       Theodore Ts'o (tytso@athena.mit.edu)


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