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DMESG(1)                                            User Commands                                            DMESG(1)

       dmesg - print or control the kernel ring buffer

       dmesg [options]

       dmesg --clear
       dmesg --read-clear [options]
       dmesg --console-level level
       dmesg --console-on
       dmesg --console-off

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

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

       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, --reltime
              Display the local time and delta in human readable format.

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

       -F, --file file
              Read log from file.

       -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, --human
              Enable human readable output.  See also --color, --reltime and --nopager.

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

       -k, --kernel
       -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 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.

       -P, --nopager
              Do not pipe output into a pager, the pager is enabled for --human output.

       -r, --raw
              Print the raw message buffer, i.e., do not strip the log level prefixes.

              Note that the real raw format depends on method how dmesg(1) reads kernel messages. The /dev/kmsg  uses
              different  format than syslog(2).  For backward compatibility dmesg(1) returns data always in syslog(2)
              format. The real raw data from /dev/kmsg is possible to read for example by  command  'dd  if=/dev/kmsg

       -S, --syslog
              Force to use syslog(2) kernel interface to read kernel messages. The default is to use /dev/kmsg rather
              than syslog(2) since kernel 3.5.0.

       -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
              Do not print kernel's timestamps.

       -u, --userspace
              Print userspace messages.

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

       -w, --follow
              Wait for new messages. This feature is supported on systems with readable /dev/kmsg only (since  kernel

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