console

Kernel Module - netconsole

Evan Davies

• 1 min read

The netconsole kernel module

If you do not have the hardware, wich is common because most laptops do not come with a COM port nowadays, you can use the netconsole module wich is very handy. It uses very low level network device calls to send via UDP console output across your network. It is included in the standard debian kernel. Using this may help you debug anything but your network device controller driver. In /etc/modprobe.d/, add a file that reads :

options netconsole netconsole=32769@192.168.1.1/eth1 \
32769@192.168.1.6/01:23:34:56:78:9A

Where :

  • 192.168.1.1:32769 on eth1 is the ip/port/interface to use the send output from.
  • 192.168.1.6:32769 and mac address 01:23:34:56:78:9A is the ip/port/mac to send packets to.

On the 192.168.1.6 box, run :

$ nc -l -p 32769 -u

Then, simply modprobe netconsole on 192.168.1.1 and output should start to appear on 192.168.1.6.

More information on Using Netconsole to See Kernel Messages.

Nothing shows when my kernel hangs!

This is the worse case scenario. Linux is usually very talkative. At this point, there is a very good chance that your problem is hardware related :

  • Try to reproduce with very few peripherals connected.
  • Check you CPU temperature.
  • The odds are good that your RAM stick has defects (this is what happened to me), so try another one.
  • Do not say that you hate hardware and try to remember what it was like back in the other OS days…

Good luck, because I know this is very annoying!