JProfiler is a great tool, however under 32 bit Ubuntu you can run into the problem of having a too low limit for open filehandles. This is a problem for JProfiler because it uses temporary files to work around the address-space limitation created by 32 bit (yeah, I know, I should upgrade to 64 bit – but 32 bit works great for now…)

To raise the maximum filehandle limit, do the following:

sudo gedit /etc/security/limits.conf
# add the following two lines before the # End of file marker
# yes, the initial star is also part of line, and you should add it
*       hard    nofile  4096
*       soft    nofile  4096
sudo gedit /etc/sysctl.conf
# restart your system

You can check if the changes were successful by using the ulimit command:

ulimit -n
# it should print out 4096