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Earlier notes about running Java on Linux can be found here, including details on how to rebuild the Linux kernel and thread library to support a high number of threads. These steps are no longer required if you use Blackdown JDK 1.2.2 RC 4 with the Inprise just-in-time compiler on Red Hat Linux 6.0 or later (or its equivalent), as described below.

Linux

For Linux we recommend that you run VolanoChat using Blackdown JDK 1.2.2 Release Candidate 4 with the Inprise just-in-time compiler on a Linux 2.2 kernel such as Red Hat Linux 6.0 or later.

Blackdown JDK 1.2.2 Release Candidate 4 is available from:

• Java-Linux Ports

The Inprise just-in-time compiler for Linux is available from:

• JBuilder Java 2 JIT for Linux

Since you will be using green threads instead of native threads, you can run Blackdown JDK 1.2.2 Release Candidate 4 on Red Hat Linux 6.0 or its equivalent (Linux 2.2.5-15, glibc 2.1.1-6) in addition to their stated requirements of Red Hat Linux 6.1 or its equivalent (Linux 2.2.12-20, glibc 2.1.2-11).

Some Java ports for Linux may depend on the versions of the Linux kernel and the C libraries you're using. Red Hat uses the following versions in its most recent Linux distributions:

Distribution  Linux   Glibc
Red Hat 5.2   2.0.36  2.0.7
Red Hat 6.0   2.2.5   2.1.1
Red Hat 6.1   2.2.12  2.1.2

Starting VolanoChat

Make sure to use the "-green" option when starting the VolanoChat server in order to use the green user-level threads version instead of the native threads version. After installing the Inprise just-in-time compiler, you can tell the Blackdown Java VM to use it by setting the "java.compiler" system property. The full command is:

java -green -Djava.compiler=javacomp COM.volano.Main

See our Server Support page for additional information about the initial heap and stack sizes you may want to define.

File descriptors

When running on the Linux 2.2.5-15 kernel (or later), each process is limited by default to 1,024 file descriptors. Since the VolanoChat server requires one file descriptor for each person chatting through a VolanoChat applet, you are limited by default to a maximum of 1,024 simultaneous users when using the Linux 2.2 kernel.

To increase the maximum file descriptors per process to 4,096 do the following:

1. Allow users to increase their file descriptor limits by changing the following configuration files:

   In /etc/security/limits.conf, add the lines:

   *       soft    nofile  1024
   *       hard    nofile  4096
   

   In /etc/pam.d/login, add:

   session required /lib/security/pam_limits.so
   

2. Increase the system-wide file descriptor limit by adding the following three lines to the /etc/rc.d/rc.local startup script:

   # Increase system-wide file descriptor limit.
   echo  8192 > /proc/sys/fs/file-max
   echo 24576 > /proc/sys/fs/inode-max
   

You can then increase the file descriptor limit under the user id you use to start VolanoChat by using the "ulimit" command (under Bash) or the "limit" command (under the C shell). See the Server Support page for sample UNIX shell startup scripts for the VolanoChat server.