I am new to Linux and I have a hard time making klogd work properly to display debug messages.
I'm writing Linux driver modules using insmod and rmmod. I have kprint output debug messages but I need to figure out how to have klogd display the debug messages.
It looks like klogd was already initialized during the boot up process (I'm using Ubuntu). So when I entered:
$ klogd -c 8
It says klogd is already running. The question is what do I need to do to prevent klogd from being initialized. And if there is any way to reintialize klogd to a higher level (8) so I can see the debug messages.
This Question has been solved and asker verified All Experts Exchange premium technology solutions are available to subscription members.
Experts Exchange has been collecting answers to technology questions since 1996…3 million and counting! If you have a question, chances are we already have your answer.
If you can't find the exact answer you're looking for, ask our exclusive community of 50,000 experts. You’ll get a personalized answer from a trusted professional.
Thousands of free tech tips, tricks, how-to’s and tutorials are available in our peer reviewed articles section. See for yourself how smart our experts are, no login required.
Save solutions to your questions, answers you’ve discovered through searching plus helpful articles in your personal knowledgebase for easy future access.
Access the answers to your technology questions today.
30-day free trial. Register in 60 seconds.
Members of the expert community talk about why the experience at Experts Exchange is different than what you will find anywhere else.
Try it out and discover for yourself.
30-day free trial. Register in 60 seconds.
Join the community of experts here and help other tech pros by answering question in your area of expertise. You can earn FREE access to all Experts Exchange's premium features and resources.
Duncan:
Yes I mean printk. What I actually want to see are the messages displaying interactively. I would prefer to see those debug messages in the same window after I type the command insmod...
I remember I was able to do that when we were developing driver modules for an embedded Linux device. With the embedded device we were able to customize the environment, I wonder how to do that on a desktop.
The -c argument to klogd affects what goes to the *console*. That is not the same as your current X window - if not running X then it is the VC1. X has/had xconsole which seems to have stopped working for me. Perhaps you can tell syslogd to rout kernel messages to somewhere helpful (like one of your xterms - you'd have to reconfigure syslogd after you knew the pty number)
Duncan:
I think I'm confused again with all these Linux terms. What I really mean is the console, just like a DOS window or DOS box in the Windows world.
I'm new to Linux, so please can you let me know how do I configure syslogd, where is it located, and how do I find out the pty number of that console (or box, or window, whatever it is called).
All I want to see are debug messages right after I type the command insmod... in the same console box.
Your simplest method is to dispense with klogd altogether. In the attached example
- make sure /proc/kmsg exists (it's possible though unlikely that it doesn't)
- find out the pid of klogd
- kill klogd
- make sure it's gone
- cat /proc/kmsg directly in your window of choice - you'll see everything
I plugged in a USB stick to generate some messages. You don't get timestamps like you would with klogd / syslogd but I imagine that doesn't worry you
-c is not necessarily the *same* console as you are working on. It sends output to /dev/console whereas *your* console is /dev/tty (and every process's /dev/tty is potentially different). By default this displays on the first DOS-lookalike screen that you get when you boot linux (assuming you don't boot to a GUI login manager with X-windows started). Did you know you probably have 6 of these? The left & right arrow keys move between them when you also hold down the Alt key. Or you can use Ctl-Alt-{F1 - F6} to change between them. But /dev/console messages only appear on the first one.
By the way, if you background the cat command, you can have its output appear on your screen as you do other stuff:
cat /proc/kmsg&
Business Accounts
Answer for Membership
by: duncan_roePosted on 2008-02-02 at 18:41:22ID: 20807181
Do you mean printk?
You can probably just let klogd run - it intercepts kernel messages and sends them to the syslog subsystem. You might want to tune your /etc/syslog.conf to put kernel messages somewhere convenient to you.