title: Cant open cooja simulator recently but worked fine before
body: <br/>
  I am working on cooja simulator in contiki OS and it worked fine till now without any error and now its showing this error.<br/>
  Used to open cooja simulator using terminal.<br/>
  Also, upon analyzing the hard disk it still has 500 mb left and I am wondering does the memory gets used as I use cooja.<br/> 
  Help Required.<br/>
  I am unable to add image, sorry about that.<br/>
  Here is the error I am getting<br/>
  user@instant-contiki:~/contiki-2.7/tools/cooja$ ant run
  OpenJDK Client VM warning: Insufficient space for shared memory file:
     /tmp/hsperfdata_user/2806
  Try using the -Djava.io.tmpdir= option to select an alternate temp location.
  <p>Buildfile: /home/user/contiki-2.7/tools/cooja/build.xml</p>
  <p>init:</p>
  <p>compile:</p>
  <p>copy configs:</p>
  <p>jar_cooja:
  [jar] Building jar: /home/user/contiki-2.7/tools/cooja/dist/cooja.jar</p>
  <p>BUILD FAILED
  /home/user/contiki-2.7/tools/cooja/build.xml:226: Problem creating jar: No space left on device</p>
  <p>Total time: 0 seconds</p>