From Fedora Project Wiki

Setting up netconsole

Assume we have two computers on the same network.

The machine with a problem (the debugee):

IP address:

And a second machine (the debugger):

IP address:
MAC address of eth0: 00:11:22:33:44:55

The debugger

On a different machine than the one you are seeing the problem, you need to run nc -l -u 6666 This will listen on udp port 6666 for any messages.

The debugee

On the machine that you're trying to debug a problem, run (as root) modprobe netconsole netconsole=4444@,6666@

If you replace the IP/MAC addresses with those relevant to your machines/network in the command above, you should see messages appearing on the debugging machine.

For more information on netconsole, see

logging levels

You may want to raise the level of printk's that go to the console.

To do this when logged in:

dmesg -n 8

netconsole at boot - client side

Raise the level of console by default logging by adding this line to /etc/sysctl.conf:

# echo 'kernel.printk = 8 4 1 7' >> /etc/sysctl.conf

Add your network info to modprobes of netconsole:

# echo 'options netconsole netconsole=4444@,6666@' >> /etc/modprobe.d/netconsole.conf

Load netconsole at boot time

# echo modprobe netconsole >> /etc/rc.modules
# chmod +x /etc/rc.modules

Firewall config

Your netconsole server needs to accept udp on port 6666. This may require a change to your iptables rules.

Comment: does default Fedora rules allow local network connections?