How can I change localhost.localdomain in the messages written by Log4j to the Linux syslog

Question

I'm writing messages to the Linux syslog using Log4j and its SyslogAppender. The outputted messages look like this:

Oct 12 09:06:03 localhost.localdomain 3364 [Thread-5] INFO TEST MESSAGE MyApplicationLogger - This is my message

I would like to replace localhost.localdomain with the name of the server running the application but can't seem to figure out how. Here's my configuration file, in case it's useful:

log4j.logger.MyApplicationLogger=INFO, SyslogAppender
log4j.appender.SyslogAppender=org.apache.log4j.net.SyslogAppender
log4j.appender.SyslogAppender.syslogHost=localhost
log4j.appender.SyslogAppender.Facility=USER
log4j.appender.SyslogAppender.layout=org.apache.log4j.PatternLayout
log4j.appender.SyslogAppender.layout.ConversionPattern= %-4r [%t] %-5p %c %x - %m%n
log4j.appender.SyslogAppender.source=My Application

Edit: the computer name is configured on the server and the hostname command returns the following:

$ hostname
server12

I do notice however that the first line of the hosts file is

127.0.0.1   localhost.localdomain localhost

However I'm hesitant to change this.

Answer 1

This is what you need:

log4j.appender.SyslogAppender.header = true

Answer 2

This issue is because your machine doesn't know it's own host name. This can be demonstrated by running the command hostname as a non-privileged user.

If you have root privileges then you can set your host name using

$ hostname myServersHostname

man page

To make this change permanent across reboots you will need to set a configuration file somewhere in /etc (exactly which one depends on your distro).

• Debian/ubuntu: /etc/hostname
• Redhat/CentOS/Fedora: /etc/sysconfig/network

Answer 3

I figured out how to fix it, so I might as well leave the solution here in case other people face the same problem.

In the properties file, put this:

log4j.appender.SyslogAppender.syslogHost=server12

Not sure why it works, but using the server name instead of localhost worked for me.

Answer 4

If you don't want to 'hard code' the hostname in the log4j properties or XML file, the best solution is a combination of what is suggested by dtyler and yegor256. Make sure your hostname is set correctly, and then use log4j.appender.SyslogAppender.header = true or <param name="Header" value="true"/> in your log4j.xml