dmesg


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.

       -n, --console-level level
              Set the level at which logging of messages is done to  the  con-
              sole.  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 console.  All
              levels of messages are still  written  to  /proc/kmsg,  so  sys-
              logd(8)  can  still be used to control exactly where kernel mes-
              sages 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  inaccu-
              rate!

              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 <kzak@redhat.com>
       Theodore Ts'o <tytso@athena.mit.edu>

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