DMESG(1)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 User Commands\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 DMESG(1)<\/p>\n
NAME<\/p>\n
dmesg – print or control the kernel ring buffer<\/p>\n
SYNOPSIS<\/p>\n
dmesg [options]<\/p>\n
dmesg –clear
\ndmesg –read-clear [options]
\ndmesg –console-level level
\ndmesg –console-on
\ndmesg –console-off<\/p>\n
DESCRIPTION<\/p>\n
dmesg is used to examine or control the kernel ring buffer.<\/p>\n
The default action is to display all messages from the kernel ring
\nbuffer.<\/p>\n
OPTIONS<\/p>\n
The –clear, –read-clear, –console-on, –console-off, and
\n–console-level options are mutually exclusive.<\/p>\n
-C, –clear
\nClear the ring buffer.<\/p>\n
-c, –read-clear
\nClear the ring buffer after first printing its contents.<\/p>\n
-D, –console-off
\nDisable the printing of messages to the console.<\/p>\n
-d, –show-delta
\nDisplay the timestamp and the time delta spent between
\nmessages.\u00a0 If used together with –notime then only the time
\ndelta without the timestamp is printed.<\/p>\n
-E, –console-on
\nEnable printing messages to the console.<\/p>\n
-e, –reltime
\nDisplay the local time and the delta in human-readable format.<\/p>\n
-F, –file file
\nRead the messages from the given file.<\/p>\n
-f, –facility list
\nRestrict output to the given (comma-separated) list of
\nfacilities.\u00a0 For example:<\/p>\n
dmesg –facility=daemon<\/p>\n
will print messages from system daemons only.\u00a0 For all
\nsupported facilities see the –help output.<\/p>\n
-H, –human
\nEnable human-readable output.\u00a0 See also –color, –reltime and
\n–nopager.<\/p>\n
-k, –kernel
\nPrint kernel messages.<\/p>\n
-L, –color[=when]
\nColorize important messages (enabled by default).\u00a0 The
\noptional argument when can be auto, never or always.\u00a0 If the
\nwhen argument is omitted, it defaults to auto.<\/p>\n
-l, –level list
\nRestrict output to the given (comma-separated) list of levels.
\nFor example:<\/p>\n
dmesg –level=err,warn<\/p>\n
will print error and warning messages only.\u00a0 For all supported
\nlevels see the –help output.<\/p>\n
-n, –console-level level
\nSet the level at which printing of messages is done to the
\nconsole.\u00a0 The level is a level number or abbreviation of the
\nlevel name.\u00a0 For all supported levels see the –help output.<\/p>\n
For example, -n 1 or -n alert prevents all messages, except
\nemergency (panic) messages, from appearing on the console.
\nAll levels of messages are still written to \/proc\/kmsg, so
\nsyslogd(8) can still be used to control exactly where kernel
\nmessages appear.\u00a0 When the -n option is used, dmesg will not
\nprint or clear the kernel ring buffer.<\/p>\n
-P, –nopager
\nDo not pipe output into a pager.\u00a0 A pager is enabled by
\ndefault for –human output.<\/p>\n
-r, –raw
\nPrint the raw message buffer, i.e. do not strip the log-level
\nprefixes.<\/p>\n
Note that the real raw format depends on the method how
\ndmesg(1) reads kernel messages.\u00a0 The \/dev\/kmsg device uses a
\ndifferent format than syslog(2).\u00a0 For backward compatibility,
\ndmesg(1) returns data always in the syslog(2) format.\u00a0 It is
\npossible to read the real raw data from \/dev\/kmsg by, for
\nexample, the command ‘dd if=\/dev\/kmsg iflag=nonblock’.<\/p>\n
-S, –syslog
\nForce dmesg to use the syslog(2) kernel interface to read
\nkernel messages.\u00a0 The default is to use \/dev\/kmsg rather than
\nsyslog(2) since kernel 3.5.0.<\/p>\n
-s, –buffer-size size
\nUse a buffer of size to query the kernel ring buffer.\u00a0 This is
\n16392 by default.\u00a0 (The default kernel syslog buffer size was
\n4096 at first, 8192 since 1.3.54, 16384 since 2.1.113.)\u00a0 If
\nyou have set the kernel buffer to be larger than the default,
\nthen this option can be used to view the entire buffer.<\/p>\n
-T, –ctime
\nPrint human-readable timestamps.<\/p>\n
Be aware that the timestamp could be inaccurate!\u00a0 The time
\nsource used for the logs is not updated after system
\nSUSPEND\/RESUME.<\/p>\n
-t, –notime
\nDo not print kernel’s timestamps.<\/p>\n
–time-format format
\nPrint timestamps using the given format, which can be ctime,
\nreltime, delta or iso.\u00a0 The first three formats are aliases of
\nthe time-format-specific options.\u00a0 The iso format is a dmesg
\nimplementation of the ISO-8601 timestamp format.\u00a0 The purpose
\nof this format is to make the comparing of timestamps between
\ntwo systems, and any other parsing, easy.\u00a0 The definition of
\nthe iso timestamp is: YYYY-MM-
\nDD<T>HH:MM:SS,<microseconds><-+><timezone offset from UTC>.<\/p>\n
The iso format has the same issue as ctime: the time may be
\ninaccurate when a system is suspended and resumed.<\/p>\n
-u, –userspace
\nPrint userspace messages.<\/p>\n
-w, –follow
\nWait for new messages.\u00a0 This feature is supported only on
\nsystems with a readable \/dev\/kmsg (since kernel 3.5.0).<\/p>\n
-x, –decode
\nDecode facility and level (priority) numbers to human-readable
\nprefixes.<\/p>\n
-V, –version
\nDisplay version information and exit.<\/p>\n
-h, –help
\nDisplay help text and exit.<\/p>\n
COLORS<\/p>\n
Implicit coloring can be disabled by an empty file \/etc\/terminal-
\ncolors.d\/dmesg.disable.\u00a0 See terminal-colors.d(5) for more details
\nabout colorization configuration.<\/p>\n
The logical color names supported by dmesg are:<\/p>\n
subsys The message sub-system prefix (e.g. “ACPI:”).<\/p>\n
time\u00a0\u00a0 The message timestamp.<\/p>\n
timebreak
\nThe message timestamp in short ctime format in –reltime or
\n–human output.<\/p>\n
alert\u00a0 The text of the message with the alert log priority.<\/p>\n
crit\u00a0\u00a0 The text of the message with the critical log priority.<\/p>\n
err\u00a0\u00a0\u00a0 The text of the message with the error log priority.<\/p>\n
warn\u00a0\u00a0 The text of the message with the warning log priority.<\/p>\n
segfault
\nThe text of the message that inform about segmentation fault.<\/p>\n
SEE ALSO<\/p>\n
syslogd(8) terminal-colors.d(5)<\/p>\n
AUTHORS<\/p>\n
Karel Zak \u27e8kzak@redhat.com\u27e9<\/p>\n
dmesg was originally written by Theodore Ts’o \u27e8tytso@athena.mit.edu\u27e9<\/p>\n
AVAILABILITY<\/p>\n
The dmesg command is part of the util-linux package and is available
\nfrom Linux Kernel Archive
\n\u27e8ftp:\/\/ftp.kernel.org\/pub\/linux\/utils\/util-linux\/\u27e9.<\/p>\n
COLOPHON<\/p>\n
This page is part of the util-linux (a random collection of Linux
\nutilities) project.\u00a0 Information about the project can be found at
\n\u27e8https:\/\/www.kernel.org\/pub\/linux\/utils\/util-linux\/\u27e9.\u00a0 If you have a
\nbug report for this manual page, send it to
\nutil-linux@vger.kernel.org.\u00a0 This page was obtained from the
\nproject’s upstream Git repository
\n(git:\/\/git.kernel.org\/pub\/scm\/utils\/util-linux\/util-linux.git) on
\n2014-12-30.\u00a0 If you discover any rendering problems in this HTML ver\u2010
\nsion of the page, or you believe there is a better or more up-to-date
\nsource for the page, or you have corrections or improvements to the
\ninformation in this COLOPHON (which is not part of the original man\u2010
\nual page), send a mail to\u00a0man-pages@man7.org<\/p>\n
util-linux\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 July 2012\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 DMESG(1)<\/p>\n","protected":false},"excerpt":{"rendered":"
DMESG(1)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 User Commands\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 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 display all messages from the kernel ring buffer. OPTIONS […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_sitemap_exclude":false,"_sitemap_priority":"","_sitemap_frequency":"","footnotes":""},"categories":[8],"tags":[],"class_list":["post-314","post","type-post","status-publish","format-standard","hentry","category-shell"],"a3_pvc":{"activated":false,"total_views":0,"today_views":0},"_links":{"self":[{"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=\/wp\/v2\/posts\/314","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=314"}],"version-history":[{"count":0,"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=\/wp\/v2\/posts\/314\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=314"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=314"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.linuxboxen.dk\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=314"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}