Change open file limits on Ubuntu

Two things have to be done to increase the number of open files on ubuntu system:

1. Change /etc/security/limits.conf file, add the following two lines in the file:

   * soft nofile 4096
   * hard nofile 4096

2. Change /etc/pam.d/common-session* file, add the following line in the file:

      session required        pam_limits.so

3. (Optional)If you will be accessing the node via secure shell (ssh), you should also edit /etc/ssh/sshd_config and uncomment the following line:

    #UseLogin no

        and set its value to yes as shown here:

    UseLogin yes

To see the open file limits on process, do the following:

   cat /proc/__process_id__/limits