DMESG(8) System Manager's Manual DMESG(8)
dmesg - print or control the kernel ring buffer
dmesg [ -c ] [ -n level ] [ -s bufsize ]
dmesg is used to examine or control the kernel ring buffer.
The program helps users to print out their bootup messages. Instead of
copying the messages by hand, the user need only:
dmesg > boot.messages
and mail the boot.messages file to whoever can debug their problem.
-c Clear the ring buffer contents after printing.
Use a buffer of size bufsize 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.
Set the level at which logging of messages is done to the con-
sole. For example, -n 1 prevents all messages, expect 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
When both options are used, only the last option on the command
line will have an effect.