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.
−cClear the ring buffer contents after printing.
−sbufsizeUse 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.
−nlevelSet the level at which logging of
messages is done to the console. 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 buffer.
When both options are used, only the last option on the command line will have an effect.