.\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu)
.\" May be distributed under the GNU General Public License
.TH DMESG 8 
.SH NAME
dmesg \- print or control the kernel ring buffer
.SH SYNOPSIS
.BI "dmesg [ \-c ] [ \-n " level " ] [ \-s " bufsize " ]"
.SH DESCRIPTION
.B 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:
.RS
dmesg > boot.messages
.RE
and mail the
.I boot.messages
file to whoever can debug their problem.
.SH OPTIONS
.TP
.B \-c
clear the ring buffer contents after printing.
.TP
.BI \-s bufsize
use a buffer of bufsize to query the kernel ring buffer.  This is
8196 by default (this matches the default kernel syslog buffer size in
2.0.33 and 2.1.103).  If you have set the kernel buffer to larger than
the default then this option can be used to view the entire buffer.
.TP
.BI \-n level
set the
.I level
at which logging of messages is done to the console.  For example,
.B \-n 1
prevents all messages, expect panic messages, from appearing on the
console.  All levels of messages are still written to
.IR /proc/kmsg ,
so
.BR syslogd (8)
can still be used to control exactly where kernel messages appear.  When
the
.B \-n
option is used,
.B dmesg
will
.I not
print or clear the kernel ring buffer.

When both options are used, only the last option on the command line will
have an effect.
.SH SEE ALSO
.BR syslogd (8)
.SH AUTHOR
Theodore Ts'o (tytso@athena.mit.edu)