title: Ubuntu 16 gives "fork: retry: Resource temporarily unavailable", Ubuntu 20 doesn't
body: <p>I have 2 similar machines in terms of HW. One has Ubuntu 16, the other Ubuntu 20.</p>
  <p>I'm running a python program that is meant to open 30K TCP connections to an end point. The Ubuntu 20 machine machine was able to do the job well just by doing these 2 commands before executing the program:</p>
  <p>#ulimit -n 1000000
  #ulimit -u 1000000</p>
  <p>However the Ubuntu 16 machine after creating 12K connections gives this:</p>
  <p>-su: fork: retry: No child processes
  -su: fork: retry: Resource temporarily unavailable
  -su: fork: retry: Resource temporarily unavailable
  -su: fork: retry: Resource temporarily unavailable</p>
  <p>Any idea what may be causing Ubuntu 16 to behave like that while Ubuntu 20 seems fine?</p>
  <p>Note: I tried to do few things now from different posts but none has worked.</p>
  <p>Thanks in advance.</p>