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1.5. Configuring netconsole
If disk logging fails or using the serial console is not possible, you might need to use kernel debugging. The
netconsole
kernel module enables to log kernel messages to another computer over the network.
To be able to use
netconsole
, you need to have an rsyslog
server that is properly configured on your network.
Procedure 1.1. Configuring an rsyslog server for netconsole
- Configure the
rsyslogd
daemon to listen on the 514/udp port and receive messages from the network by uncommenting the following lines in theMODULES
section of the/etc/rsyslog.conf
file:$ModLoad imudp $UDPServerRun 514
- Restart the
rsyslogd
service for the changes to take effect:]#
systemctl restart rsyslog
- Verify that
rsyslogd
is listening on the 514/udp port:]#
netstat -l | grep syslog
udp 0 0 0.0.0.0:syslog 0.0.0.0:* udp6 0 0 [::]:syslog [::]:*The0.0.0.0:syslog
and[::]:syslog
values in thenetstat -l
output mean thatrsyslogd
is listening on defaultnetconsole
port defined in the/etc/services
file:]$
cat /etc/services | grep syslog
syslog 514/udp syslog-conn 601/tcp # Reliable Syslog Service syslog-conn 601/udp # Reliable Syslog Service syslog-tls 6514/tcp # Syslog over TLS syslog-tls 6514/udp # Syslog over TLS syslog-tls 6514/dccp # Syslog over TLS
Netconsole
is configured using the /etc/sysconfig/netconsole
file, which is a part of the initscripts package. This package is installed by default and it also provides the netconsole
service.
If you want to configure a sending machine, follow this procedure:
Procedure 1.2. Configuring a Sending Machine
- Set the value of the
SYSLOGADDR
variable in the/etc/sysconfig/netconsole
file to match the IP address of thesyslogd
server. For example:SYSLOGADDR=192.168.0.1
- Restart the
netconsole
service for the changes to take effect:]#
systemctl restart netconsole.service
- Enable
netconsole.service
to run after rebooting the system:]#
systemctl enable netconsole.service
- View the
netconsole
messages from the client in the/var/log/messages
file (default) or in the file specified inrsyslog.conf
.]#
cat /var/log/messages
Note
By default,
rsyslogd
and netconsole.service
use port 514. To use a different port, change the following line in /etc/rsyslog.conf
to the required port number:
$UDPServerRun <PORT>
On the sending machine, uncomment and edit the following line in the
/etc/sysconfig/netconsole
file:
SYSLOGPORT=514
For more information about
netconsole
configuration and troubleshooting tips, see Netconsole Kernel Documentation.