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,
−−clear
Clear the ring buffer.
−c,
−−read−clear
Clear the ring buffer contents after printing.
−D,
−−console−off
Disable printing messages to the console.
−d,
−−show−delta
Display 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−on
Enable 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,
−−help
Print a help text and exit.
−k,
−−kernel
Print 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
level
Set 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,
−−raw
Print 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,
−−ctime
Print human readable timestamps. The timestamp could be inaccurate!
The time source used for the logs is not updated after system SUSPEND/RESUME.
−t,
−−notime
Don't print kernel's timestampts.
−u,
−−userspace
Print userspace messages.
−V,
−−version
Output version information and exit.
−x,
−−decode
Decode facility and level (priority) number to human readable prefixes.