DMESG(1)						   User Commands						  DMESG(1)



NAME
       dmesg - print or control the kernel ring buffer

SYNOPSIS
       dmesg [options]

       dmesg --clear

       dmesg --read-clear [options]

       dmesg --console-level level

       dmesg --console-on

       dmesg --console-off

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

       The default action is to read all messages from kernel ring buffer.


OPTIONS
       The --clear, --read-clear, --console-on, --console-off and --console-level options are mutually exclusive.


       -C, --clear
	      Clear the ring buffer.

       -c, --read-clear
	      Clear the ring buffer contents after printing.

       -D, --console-off
	      Disable printing messages to the console.

       -d, --show-delta
	      Display the timestamp and time delta spent between messages. If used together with --notime then only the time delta
	      without the timestamp is printed.

       -E, --console-on
	      Enable printing messages to the console.

       -f, --facility list
	      Restrict output to defined (comma separated) list of facilities. For example

		dmesg --facility=daemon

	      will print messages from system daemons only. For all supported facilities see dmesg --help output.

       -h, --help
	      Print a help text and exit.

       -k, --kernel
	      Print kernel messages.

       -l, --level list
	      Restrict output to defined (comma separated) list of levels. For example

		dmesg --level=err,warn

	      will print error and warning messages only. For all supported levels see dmesg --help output.

       -n, --console-level level
	      Set the level at which logging of messages is done to the console. The level is a level number  or  abbreviation	of
	      the level name. For all supported levels see dmesg --help output.

	      For  example,  -n 1 or -n alert prevents all messages, except emergency (panic) messages, from appearing on the con‐
	      sole.  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.

       -r, --raw
	      Print the raw message buffer, i.e., don't strip the log level prefixes.

       -s, --buffer-size size
	      Use  a buffer of size 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.

       -T, --ctime
	      Print human readable timestamps. The timestamp could be inaccurate!

	      The time source used for the logs is not updated after system SUSPEND/RESUME.

       -t, --notime
	      Don't print kernel's timestampts.

       -u, --userspace
	      Print userspace messages.

       -V, --version
	      Output version information and exit.

       -x, --decode
	      Decode facility and level (priority) number to human readable prefixes.

SEE ALSO
       syslogd(8)

AUTHORS
       Karel Zak 
       Theodore Ts'o 

AVAILABILITY
       The dmesg command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.



util-linux						     July 2011							  DMESG(1)