sys-utils/dmesg.1

   1 .\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu)
   2 .\" May be distributed under the GNU General Public License
   3 .TH DMESG 1 "Jun 2011"
   4 .SH NAME
   5 dmesg \- print or control the kernel ring buffer
   6 .SH SYNOPSIS
   7 .B dmesg
   8 .RB [ options ]
   9 .sp
  10 .B dmesg \-\-clear
  11 .sp
  12 .B dmesg \-\-read-clear
  13 .RB [ options ]
  14 .sp
  15 .B dmesg \-\-console-level
  16 .I level
  17 .sp
  18 .B dmesg \-\-console-on
  19 .sp
  20 .B dmesg \-\-console-off
  21 .SH DESCRIPTION
  22 .B dmesg
  23 is used to examine or control the kernel ring buffer.
  24
  25 The default action is to read all messages from kernel ring buffer.
  26
  27 .SH OPTIONS
  28 The --clear, --read-clear, --console-on, --console-off and --console-level
  29 options are mutually exclusive.
  30
  31 .IP "\fB\-C, \-\-clear\fP"
  32 Clear the ring buffer.
  33 .IP "\fB\-c, \-\-read-clear\fP"
  34 Clear the ring buffer contents after printing.
  35 .IP "\fB\-d, \-\-console-off\fP"
  36 Disable printing messages to the console.
  37 .IP "\fB\-e, \-\-console-on\fP"
  38 Enable printing messages to the console.
  39 .IP "\fB\-h, \-\-help\fP"
  40 Print a help text and exit.
  41 .IP "\fB\-n, \-\-console-level \fIlevel\fP
  42 Set the
  43 .I level
  44 at which logging of messages is done to the console. The
  45 .I level
  46 is a level number or abbreviation of the level name. For all supported levels see
  47 .B dmesg \-\-help
  48 output.
  49 .sp
  50 For example,
  51 .B \-n 1
  52 or
  53 .B \-n alert
  54 prevents all messages, except emergency (panic) messages, from appearing on the
  55 console.  All levels of messages are still written to
  56 .IR /proc/kmsg ,
  57 so
  58 .BR syslogd (8)
  59 can still be used to control exactly where kernel messages appear.  When
  60 the
  61 .B \-n
  62 option is used,
  63 .B dmesg
  64 will
  65 .I not
  66 print or clear the kernel ring buffer.
  67 .IP "\fB\-r, \-\-raw\fP"
  68 Print the raw message buffer, i.e., don't strip the log level prefixes.
  69 .IP "\fB\-s, \-\-buffer-size \fIsize\fP
  70 Use a buffer of
  71 .I size
  72 to query the kernel ring buffer.  This is 16392 by default.
  73 (The default kernel syslog buffer size was 4096
  74 at first, 8192 since 1.3.54, 16384 since 2.1.113.)
  75 If you have set the kernel buffer to be larger than the default
  76 then this option can be used to view the entire buffer.
  77 .IP "\fB\-V, \-\-version\fP"
  78 Output version information and exit.
  79 .SH SEE ALSO
  80 .BR syslogd (8)
  81 .\" .SH AUTHOR
  82 .\" Theodore Ts'o (tytso@athena.mit.edu)
  83 .SH AVAILABILITY
  84 The dmesg command is part of the util-linux package and is available from
  85 ftp://ftp.kernel.org/pub/linux/utils/util-linux/.