Hadoop webuser: No such user

While running a hadoop multi-node cluster , i got below error message on my master logs , can some advise what to do..? do i need to create a new user or can i gave my existing Machine user name over here

2013-07-25 19:41:11,765 WARN org.apache.hadoop.security.UserGroupInformation: No groups available for user webuser 2013-07-25 19:41:11,778 WARN org.apache.hadoop.security.ShellBasedUnixGroupsMapping: got exception trying to get groups for user webuser org.apache.hadoop.util.Shell$ExitCodeException: id: webuser: No such user

hdfs-site.xml file

<configuration>
<property>
  <name>dfs.replication</name>
  <value>2</value>
  <description>Default block replication.
  The actual number of replications can be specified when the file is created.
  The default is used if replication is not specified in create time.
  </description>
</property>

</configuration>

core-site.xml

<configuration>
<property>
  <name>fs.default.name</name>
  <value>hdfs://master:54310</value>
  <description>The name of the default file system.  A URI whose
  scheme and authority determine the FileSystem implementation.  The
  uri's scheme determines the config property (fs.SCHEME.impl) naming
  the FileSystem implementation class.  The uri's authority is used to
  determine the host, port, etc. for a filesystem.</description>
</property>

</configuration>

mapred-site.xml

<configuration>
<property>
  <name>mapred.job.tracker</name>
  <value>master:54311</value>
  <description>The host and port that the MapReduce job tracker runs
  at.  If "local", then jobs are run in-process as a single map
  and reduce task.
  </description>
</property>

</configuration>

i followed http://www.michael-noll.com/tutorials/running-hadoop-on-ubuntu-linux-multi-node-cluster/ .

Hadoop 1.2.0 jetty-6.1.26

After adding my hdfs-site.xml looks

<configuration>
<property>
  <name>dfs.replication</name>
    <value>2</value>
      <description>Default block replication.
        The actual number of replications can be specified when the file is created.
          The default is used if replication is not specified in create time.
 </description>
</property>
<property>
<name>dfs.web.ugi</name>
<value>hduser,hadoop</value>
</property>
</configuration>

Edit the dfs.web.ugi property in hdfs-site.xml and add your user there. It is by default webuser,webgroup.