Linux in a Nutshell, Third Edition

Name

klogd

Synopsis

klogd [options]

Description

System administration command. Control which kernel messages are displayed on the console; prioritize all messages, and log them through syslogd. On many operating systems, syslogd performs all the work of klogd, but on Linux the features are separated. Kernel messages are gleaned from the /proc filesystem and from system calls to syslogd. By default, no messages appear on the console. Messages are sorted into 8 levels, 0-7, and the level number is prepended to each message.

Priority levels

0

Emergency situation (KERN_EMERG).

1

A crucial error has occurred (KERN_ALERT).

2

A serious error has occurred (KERN_CRIT).

3

An error has occurred (KERN_ERR).

4

A warning message (KERN_WARNING).

5

The situation is normal but should be checked (KERN_NOTICE).

6

Information only (KERN_INFO).

7

Debugging messages (KERN_DEBUG).

Options

-c level

Print all messages of a higher priority (lower number) than level to the console.

-d

Debugging mode.

-f file

Print all messages to file; suppress normal logging.

-k file

Use file as source of kernel symbols.

-n

Avoid autobackgrounding. This is needed when klogd is started from init.

-o

One-shot mode. Prioritize and log all current messages, then immediately exit.

-s

Suppress reading of messages from the /proc filesystem.

Files

/usr/include/linux/kernel.h, /usr/include/sys/syslog.h

Sources for definitions of each logging level

/proc/kmsg

A file examined by klogd for messages

/var/run/klogd.pid

klogd’s process ID ...