From Power Up To Bash Prompt

9. System Logger

Init starts the syslogd and klogd daemons. They write messages to logs. The kernel's messages are handled by klogd, while syslogd handles log messages from other processes. The main log is /var/log/messages. This is a good place to look if something is going wrong with your system. Often there will be a valuable clue in there.

9.1 Configuration

The file /etc/syslog.conf tells the loggers what messages to put where. Messages are identified by which service they come from, and what priority level they are. This configuration file consists of lines that say messages from service x with priority y go to z, where z is a file, tty, printer, remote host or whatever.

NOTE: Syslog requires the /etc/services file to be present. The services file allocates ports. I am not sure whether syslog needs a port allocated so that it can do remote logging, or whether even local logging is done through a port, or whether it just uses /etc/services to convert the service names you type /etc/syslog.conf into port numbers.

9.2 Exercises

Have a look at your system log. Find a message you don't understand, and find out what it means.

Send all your log messages to a tty. (set it back to normal once done)

9.3 More Information

Australian sysklogd Mirror