If you are running a Cisco router and are not receiving messages, use the Logging source-interface command to specify an interface to log from.
There is a bug in the Cisco IOS that causes invalid UDP checksums unless this command is specified.
Knowing the precise message that accompanies an error can be vital in researching malfunctions in product manuals, online documentation, and Web searches.
This can be invaluable in correlating the timing and causes of related events on your system.
It is also important to know that applications frequently don't display errors on the screen, but will usually log them somewhere.
In this example messages of severity emergency and above triggers this type of notification.
I've included syslog here as a dedicated chapter to both emphasize its importance to your Linux knowledge and prepare you with a valuable skill that will help you troubleshoot all the Linux various applications that will be presented throughout the book syslog is a utility for tracking and logging all manner of system messages from the merely informational to the extremely critical.
Each system message sent to the syslog server has two descriptive labels associated with it that makes the message easier to handle.
In this case, all messages of severity "info" and above are logged, but none from the mail, cron or authentication facilities/subsystems.
You can make this logging even more sensitive by replacing the line above with one that captures all messages from debug severity and above in the You can even have certain types of messages sent to the screen of all logged in users.
If you find a message in the errorlog file stating that Kiwi Syslog Server is unable to bind to a particular port then you will need to close down the application that is using that port before restarting Kiwi Syslog Server again.
There are hundreds of Linux applications on the market, each with their own configuration files and help pages.