Display the timestamp and the time delta spent between messages. If used together with *--notime* then only the time delta without the timestamp is printed.
Display the local time and the delta in human-readable format. Be aware that conversion to the local time could be inaccurate (see *-T* for more details).
Colorize the output. The optional argument _when_ can be *auto*, *never* or *always*. If the _when_ argument is omitted, it defaults to *auto*. The colors can be disabled; for the current built-in default see the *--help* output. See also the *COLORS* section below.
Set the _level_ at which printing of messages is done to the console. The _level_ is a level number or abbreviation of the level name. For all supported levels see the *--help* output.
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For example, *-n 1* or *-n emerg* 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.
The unprintable and potentially unsafe characters (e.g., broken multi-byte sequences, terminal controlling chars, etc.) are escaped in format \x<hex> for security reason by default. This option disables this feature at all. It's usable for example for debugging purpose together with *--raw*. Be careful and don't use it by default.
Print the raw message buffer, i.e., do not strip the log-level prefixes, but all unprintable characters are still escaped (see also *--noescape*).
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Note that the real raw format depends on the method how *dmesg* reads kernel messages. The _/dev/kmsg_ device uses a different format than *syslog*(2). For backward compatibility, *dmesg* returns data always in the *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'.
Force *dmesg* to use the *syslog*(2) kernel interface to read kernel messages. The default is to use _/dev/kmsg_ rather than *syslog*(2) since kernel 3.5.0.
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.
*Be aware that the timestamp could be inaccurate!* The *time* source used for the logs is *not updated after* system *SUSPEND*/*RESUME*. Timestamps are adjusted according to current delta between boottime and monotonic clocks, this works only for messages printed after last resume.
Display record since the specified time. The time is possible to specify in absolute way as well as by relative notation (e.g. '1 hour ago'). Be aware that the timestamp could be inaccurate and see *--ctime* for more details.
Display record until the specified time. The time is possible to specify in absolute way as well as by relative notation (e.g. '1 hour ago'). Be aware that the timestamp could be inaccurate and see *--ctime* for more details.
Print timestamps using the given _format_, which can be *ctime*, *reltime*, *delta* or *iso*. The first three formats are aliases of the time-format-specific options. The *iso* format is a *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 *iso* timestamp is: YYYY-MM-DD<T>HH:MM:SS,<microseconds><-+><timezone offset from UTC>.
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The *iso* format has the same issue as *ctime*: the time may be inaccurate when a system is suspended and resumed.
Implicit coloring can be disabled by an empty file _/etc/terminal-colors.d/dmesg.disable_. See *terminal-colors.d*(5) for more details about colorization configuration.
*dmesg* can fail reporting permission denied error. This is usually caused by *dmesg_restrict* kernel setting, please see *syslog*(2) for more details.
== AUTHORS
mailto:kzak@redhat.com[Karel Zak]
*dmesg* was originally written by mailto:tytso@athena.mit.edu[Theodore Ts'o].