DMESG(8)

NAME
dmesg - display the system message buffer

SYNOPSIS
dmesg [-a] [-c] [-f[f]] [-M core] [-N system] [-n dumpnr]

DESCRIPTION
The dmesg utility displays the contents of the system message buffer. If neither the -N nor the -M option is specified, the buffer is read from the currently running kernel via the sysctl(3) interface. Otherwise, the buffer is read from the specified core file (or from the default one), using the name list from the specified kernel image (or from the default image).

The options are as follows:

-a  Show all data in the message buffer. This includes any syslog records and /dev/console output.

-c  Clear the kernel buffer after printing.

-f[f]
    After the initial message buffer dump dmesg monitors the kernel for additional data and displays it as it arrives. dmesg will not terminate until killed in this mode. If this option is specified twice, dmesg will live loop (using the CPU heavily) to obtain updates as quickly as possible. This second mode should only be used when trying to debug a kernel crashing situation.

-M core
    Extract values associated with the name list from the specified core instead of the default /dev/kmem.

-N system
    Extract the name list from the specified system instead of the default, which is the kernel image the system has booted from.

-n dumpnr
    Use the kernel core dump file numbered dumpnr for debugging. If not found in the current directory, /var/crash is checked.

FILES
/var/run/dmesg.boot
    usually a snapshot of the buffer contents taken soon after file systems are mounted at startup time

SEE ALSO
sysctl(3), syslogd(8)

HISTORY
The dmesg utility appeared in 3.0BSD.