summaryrefslogtreecommitdiffstats
path: root/sys-utils/dmesg.1
diff options
context:
space:
mode:
authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-06 02:42:50 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-06 02:42:50 +0000
commit8cb83eee5a58b1fad74c34094ce3afb9e430b5a4 (patch)
treea9b2e7baeca1be40eb734371e3c8b11b02294497 /sys-utils/dmesg.1
parentInitial commit. (diff)
downloadutil-linux-upstream/2.33.1.tar.xz
util-linux-upstream/2.33.1.zip
Adding upstream version 2.33.1.upstream/2.33.1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r--sys-utils/dmesg.1256
1 files changed, 256 insertions, 0 deletions
diff --git a/sys-utils/dmesg.1 b/sys-utils/dmesg.1
new file mode 100644
index 0000000..a93821a
--- /dev/null
+++ b/sys-utils/dmesg.1
@@ -0,0 +1,256 @@
+.\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu)
+.\" May be distributed under the GNU General Public License
+.TH DMESG "1" "July 2012" "util-linux" "User Commands"
+.SH NAME
+dmesg \- print or control the kernel ring buffer
+.SH SYNOPSIS
+.B dmesg
+[options]
+.sp
+.B dmesg \-\-clear
+.br
+.BR "dmesg \-\-read\-clear " [options]
+.br
+.BI "dmesg \-\-console\-level " level
+.br
+.B dmesg \-\-console\-on
+.br
+.B dmesg \-\-console\-off
+.SH DESCRIPTION
+.B dmesg
+is used to examine or control the kernel ring buffer.
+.PP
+The default action is to display all messages from the kernel ring buffer.
+.SH OPTIONS
+The
+.BR \-\-clear ,
+.BR \-\-read\-clear ,
+.BR \-\-console\-on ,
+.BR \-\-console\-off ,
+and
+.B \-\-console\-level
+options are mutually exclusive.
+.PP
+.IP "\fB\-C\fR, \fB\-\-clear\fR"
+Clear the ring buffer.
+.IP "\fB\-c\fR, \fB\-\-read\-clear\fR"
+Clear the ring buffer after first printing its contents.
+.IP "\fB\-D\fR, \fB\-\-console\-off\fR"
+Disable the printing of messages to the console.
+.IP "\fB\-d\fR, \fB\-\-show\-delta\fR"
+Display the timestamp and the time delta spent between messages. If used
+together with
+.B \-\-notime
+then only the time delta without the timestamp is printed.
+.IP "\fB\-E\fR, \fB\-\-console\-on\fR"
+Enable printing messages to the console.
+.IP "\fB\-e\fR, \fB\-\-reltime\fR"
+Display the local time and the delta in human-readable format. Be aware that
+conversion to the local time could be inaccurate (see \fB\-T\fR for more
+details).
+.IP "\fB\-F\fR, \fB\-\-file \fIfile\fR"
+Read the syslog messages from the given
+.IR file .
+Note that \fB\-F\fR does not support messages in kmsg format. The old syslog format is supported only.
+.IP "\fB\-f\fR, \fB\-\-facility \fIlist\fR"
+Restrict output to the given (comma-separated)
+.I list
+of facilities. For example:
+.PP
+.RS 14
+.B dmesg \-\-facility=daemon
+.RE
+.IP
+will print messages from system daemons only. For all supported facilities
+see the
+.B \-\-help
+output.
+.IP "\fB\-H\fR, \fB\-\-human\fR"
+Enable human-readable output. See also \fB\-\-color\fR, \fB\-\-reltime\fR
+and \fB\-\-nopager\fR.
+.IP "\fB\-k\fR, \fB\-\-kernel\fR"
+Print kernel messages.
+.IP "\fB\-L\fR, \fB\-\-color\fR[=\fIwhen\fR]"
+Colorize the output. The optional argument \fIwhen\fP
+can be \fBauto\fR, \fBnever\fR or \fBalways\fR. If the \fIwhen\fR argument is omitted,
+it defaults to \fBauto\fR. The colors can be disabled; for the current built-in default
+see the \fB\-\-help\fR output. See also the \fBCOLORS\fR section below.
+.IP "\fB\-l\fR, \fB\-\-level \fIlist\fR"
+Restrict output to the given (comma-separated)
+.I list
+of levels. For example:
+.PP
+.RS 14
+.B dmesg \-\-level=err,warn
+.RE
+.IP
+will print error and warning messages only. For all supported levels see the
+.B \-\-help
+output.
+.IP "\fB\-n\fR, \fB\-\-console\-level \fIlevel\fR
+Set the
+.I level
+at which printing of messages is done to the console. The
+.I level
+is a level number or abbreviation of the level name. For all supported
+levels see the
+.B \-\-help
+output.
+.sp
+For example,
+.B \-n 1
+or
+.B \-n emerg
+prevents all messages, except emergency (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.
+.IP "\fB\-P\fR, \fB\-\-nopager\fR"
+Do not pipe output into a pager. A pager is enabled by default for \fB\-\-human\fR output.
+.IP "\fB\-p\fR, \fB\-\-force\-prefix\fR"
+Add facility, level or timestamp information to each line of a multi-line message.
+.IP "\fB\-r\fR, \fB\-\-raw\fR"
+Print the raw message buffer, i.e. do not strip the log-level prefixes.
+
+Note that the real raw format depends on the method how
+.BR dmesg (1)
+reads kernel messages. The /dev/kmsg device uses a different format than
+.BR syslog (2).
+For backward compatibility,
+.BR dmesg (1)
+returns data always in the
+.BR syslog (2)
+format. It is possible to read the real raw data from /dev/kmsg by, for example,
+the command 'dd if=/dev/kmsg iflag=nonblock'.
+.IP "\fB\-S\fR, \fB\-\-syslog\fR"
+Force \fBdmesg\fR to use the
+.BR syslog (2)
+kernel interface to read kernel messages. The default is to use /dev/kmsg rather
+than
+.BR syslog (2)
+since kernel 3.5.0.
+.IP "\fB\-s\fR, \fB\-\-buffer\-size \fIsize\fR
+Use a buffer of
+.I 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.
+.IP "\fB\-T\fR, \fB\-\-ctime\fR"
+Print human-readable timestamps.
+.IP
+.B Be aware that the timestamp could be inaccurate!
+The
+.B time
+source used for the logs is
+.B not updated after
+system
+.BR SUSPEND / RESUME .
+.IP "\fB\-t\fR, \fB\-\-notime\fR"
+Do not print kernel's timestamps.
+.IP "\fB\-\-time\-format\fR \fIformat\fR"
+Print timestamps using the given \fIformat\fR, which can be
+.BR ctime ,
+.BR reltime ,
+.B delta
+or
+.BR iso .
+The first three formats are aliases of the time-format-specific options.
+The
+.B iso
+format is a
+.B dmesg
+implementation of the ISO-8601 timestamp format. The purpose of this format is
+to make the comparing of timestamps between two systems, and any other parsing,
+easy. The definition of the \fBiso\fR timestamp is:
+YYYY-MM-DD<T>HH:MM:SS,<microseconds><-+><timezone offset from UTC>.
+.IP
+The
+.B iso
+format has the same issue as
+.BR ctime :
+the time may be inaccurate when a system is suspended and resumed.
+.TP
+.BR \-u , " \-\-userspace"
+Print userspace messages.
+.TP
+.BR \-w , " \-\-follow"
+Wait for new messages. This feature is supported only on systems with
+a readable /dev/kmsg (since kernel 3.5.0).
+.TP
+.BR \-x , " \-\-decode"
+Decode facility and level (priority) numbers to human-readable prefixes.
+.TP
+.BR \-V , " \-\-version"
+Display version information and exit.
+.TP
+.BR \-h , " \-\-help"
+Display help text and exit.
+.SH COLORS
+Implicit coloring can be disabled by an empty file \fI/etc/terminal-colors.d/dmesg.disable\fR.
+See
+.BR terminal-colors.d (5)
+for more details about colorization configuration.
+.PP
+The logical color names supported by
+.B dmesg
+are:
+.TP
+.B subsys
+The message sub-system prefix (e.g. "ACPI:").
+.TP
+.B time
+The message timestamp.
+.TP
+.B timebreak
+The message timestamp in short ctime format in \fB\-\-reltime\fR
+or \fB\-\-human\fR output.
+.TP
+.B alert
+The text of the message with the alert log priority.
+.TP
+.B crit
+The text of the message with the critical log priority.
+.TP
+.B err
+The text of the message with the error log priority.
+.TP
+.B warn
+The text of the message with the warning log priority.
+.TP
+.B segfault
+The text of the message that inform about segmentation fault.
+.SH EXIT STATUS
+.B dmesg
+can fail reporting permission denied error. This is usually caused by
+.B dmesg_restrict
+kernel setting, please see
+.BR syslog (2)
+for more details.
+.SH SEE ALSO
+.BR terminal-colors.d (5),
+.BR syslogd (8)
+.SH AUTHORS
+.MT kzak@redhat.com
+Karel Zak
+.ME
+
+.br
+.B dmesg
+was originally written by
+.MT tytso@athena.mit.edu
+Theodore Ts'o
+.ME
+.SH AVAILABILITY
+The dmesg command is part of the util-linux package and is available from
+.UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
+Linux Kernel Archive
+.UE .