Red Hat Knowledgebase

Release Found: Red Hat Enterprise Linux 3, 4 and 5.

netconsole allows dmesg output to be transmitted via the network through the use of syslog. It implements kernel-level network logging via UDP port 514.

It is necessary to have a syslog server on the network with syslogd listening on port 514/udp. To configure a syslogd to listen to port 514/udp and to receive messages from the network, configure the /etc/sysconfig/syslog file with the following options:

SYSLOGD_OPTIONS="-m 0 -r -x"

And a restart the syslogd daemon for the changes to take effect.

service syslog restart

To verify if the syslogd is actually listening on 514/udp do:

# lsof -nn -p `pidof syslogd` | grep UDP
syslogd 2885 root 13u IPv4 6417 UDP *:syslog

In this case it is listening on UDP *:syslog, where syslog is the port 514/udp as defined in /etc/services

On Red Hat Enterprise Linux 3 and Red Hat Enterprise Linux 4 the configuration file of netconsole is /etc/sysconfig/netdump, which is provided by the netdump package. On Red Hat Enterprise Linux 5 there is no longer netdump on the system and netconsole is configured via the file /etc/sysconfig/netconsole, which is part of the initscripts package.

Therefore, to configured netconsole, it is necessary to change the SYSLOGADDR variable on the configuration file /etc/sysconfig/netdump (Red Hat Enterprise Linux 3 and Red Hat Enterprise Linux 4) and /etc/sysconfig/netconsole (Red Hat Enterprise Linux 5). This variable contains the IP address of the syslogd server.

SYSLOGADDR=192.168.0.1

Then it is necessary to start the netconsole service. On Red Hat Enterprise Linux 3 and Red Hat Enterprise Linux 4 netconsole is started on the same script as netdump, therefore:

Restart the netdump daemon:

# service netdump restart

On Red Hat Enterprise Linux 5 the service is netconsole:

# service netconsole restart

By default, the syslogd server writes the netconsole messages from the client on /var/log/messages or on the file specified in syslog.conf.