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,
−−clearClear the ring buffer.
−c,
−−read−clearClear the ring buffer contents after printing.
−D,
−−console−offDisable printing messages to the console.
−d,
−−show−deltaDisplay the timestamp and time delta spent between messages. If used together with --notime then only the time delta without the timestamp is printed.
−E,
−−console−onEnable printing messages to the console.
−f,
−−facility listRestrict 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,
−−helpPrint a help text and exit.
−k,
−−kernelPrint kernel messages.
−l,
−−level listRestrict output to defined (comma separated) list of levels. For example
dmesg --level=err,warn
will print error and warning messages only. For all supported levels see dmesg −−help output.
−n,
−−console−level levelSet 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.
−r,
−−rawPrint the raw message buffer, i.e., don't strip the log level prefixes.
−s,
−−buffer−size sizeUse 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,
−−ctimePrint human readable timestamps. The timestamp could be inaccurate!
The time source used for the logs is not updated after system SUSPEND/RESUME.
−t,
−−notimeDon't print kernel's timestampts.
−u,
−−userspacePrint userspace messages.
−V,
−−versionOutput version information and exit.
−x,
−−decodeDecode facility and level (priority) number to human readable prefixes.