netconsole is a kernel module that sends all kernel log messages (i.e. dmesg) over the network to another computer, without involving user space (e.g. syslogd). Name "netconsole" is a misnomer because it's not really a "console", more like a remote logging service.
It can be used either built-in or as a module. Built-in netconsole initializes immediately after NIC cards and will bring up the specified interface as soon as possible. The module is mainly used for capturing kernel panic output from a headless machine, or in other situations where the user space is no more functional.
Documentation is available in the Linux kernel tree under Documentation/networking/netconsole.txt
netconsole and other modules Kernel parameters can be passed from a bootloader when starting the kernel by modifying bootloader configuration file. Such modification is bootloader type and version specific. Or can pass them at runtime and restart netconsole:
# set log level for kernel messages dmesg -n 8 firstname.lastname@example.org/eth0,email@example.com/00:43:24:96:d7:v5
# set log level for kernel messages dmesg -n 8 modprobe configfs modprobe netconsole mount none -t configfs /sys/kernel/config mkdir /sys/kernel/config/netconsole/target1 cd /sys/kernel/config/netconsole/target1 # set local IP address echo 192.168.0.111 > local_ip # set destination IP address echo 192.168.0.17 > remote_ip # find destination MAC address arping `cat remote_ip` -f |grep -o ..:..:..:..:..:.. > remote_mac echo 1 > enabled
netconsole should now be configured. To verify, run 'dmesg |tail' and you should see "netconsole: network logging started"
nc -u -l 6666
nc -u -l -p 6666