Maximum simultaneous opened files in a java thread on linux 1.4.20

Question

Hello,
It seems like a maximum of 1024 files can be opened by a processus on linux (in java, a thread is a linux processus).
Is it possible to change this value, or has it been set at the JVM compilation?
I created a nio server, and one thread is to manage thousands of connections. For the moment I can't pass 1010 connections.
As a fast test, I created the following source :
public class MaxOpenedFilesTest {
/** Creates a new instance of MaxOpenedFilesTest */
public MaxOpenedFilesTest() {
* @param args the command line arguments
public static void main(String[] args) {
File f = new File("/home/greg/a.out");
FileInputStream[] stream = new FileInputStream[2000];
try {
for (int i=0; i<stream.length; i++) {
stream[i] = new FileInputStream(f);
System.out.println(i+" files opened");
catch (Exception e) {
System.out.println("ERROR : "+e);
e.printStackTrace();
This test throws an IOException at 1019 files opened : Too many opened files...
I have tested a lot of things. I even recompiled the linux kernel. Changed the NR_OPEN, OPEN_MAX, __FD_SETSIZE, etc... Still don't work.
I havve set the global maximum file descriptor to 65536. It works. But for one thread, I can't have more than 1019 file descriptors (must be the 1024 initial limit defined by the kernel)...
Could somebody help.
It would be great.
Thank you.
Gr�goire.

Answer 1

Thank you for your answer.
I have already done all the described procedures in the link you provided.
In fact, I used this link :
file:///home/greg/1_NetNoLedge/LinuxTuning/linux.html
and this other one :
file:///home/greg/1_NetNoLedge/LinuxTuning/s1-custom-kernel-modularized.html
Still only 1024 files allowed to be opened for one process...
In your link, it is said :
You need to give processes the option of increasing their file descriptor limits:
In /etc/security/limits.conf add two lines:
* soft nofile 1024
* hard nofile 4096
Suggesting that it wouldn't even be necessary recompile the kernel to allow more opened file descriptors in a process... This really isn't clear for me.
Thank you.