I have a java app on a large instance that will spawn up to 800 threads. I can run the application fine as user "root" but not as another user which I created. I get the deadly. java.lang.OutOfMemoryError: unable to create new native thread at java.lang.Thread.start0(Native Method) at java.lang.Thread.start(Thread.java:657) at java.util.concurrent.ThreadPoolExecutor.addWorker(ThreadPoolExecutor.java:943) at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1325) nightmare. I have tried increasing the stack size already in limits.conf to no avail. Please, help me out. What is different here for the root and other user?