Hadoop 2.4.1 How to clear usercache

[arthur.hk.c...@gmail.com]

Hi, 

 i use Hadoop 2.4.1, in my cluster,  Non DFS Used: 2.09 TB

I found that these files are all under tmp/nm-local-dir/usercache

Is there any Hadoop command to remove these unused user cache files 
tmp/nm-local-dir/usercache ?

Regards
Arthur