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dmesg command man page

DMESG(8)      DMESG(8)

       dmesg - print or control the kernel ring buffer
       dmesg [ -c ] [ -n level ] [ -s bufsize ]

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

       The program helps users to print out their bootup messages.  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.

       -c     Clear the ring buffer contents after printing.

     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.

     Set the level at which logging of messages is done to  the  con-
     sole.   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

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




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