title: What does "soft/hard nofile" mean on Linux
body: <p>When I tried to install a software on RedHat EL5, I got the error that the expected value of soft/hard nofile is 4096 while the default is 1024. I managed to increase the number, but I don't know what the parameters are. Are they refering to soft link and hard link?</p>
  
  <p>The way I change it is:</p>
  
  <p>A) modify the /etc/security/limits.conf</p>
  
  <pre><code>user soft nofile 5000
  user hard nofile 6000
  </code></pre>
  
  <p>B) modify the /etc/pam.d/system-auth </p>
  
  <pre><code>session required /lib/security/$ISA/pam_limits.so
  </code></pre>
  
  <p>C) modify /etc/pam.d/login</p>
  
  <pre><code>session required pam_limits.so
  </code></pre>
  
  <p>After making the change (by switching to root). It seems that I have to reboot machine to make it effect. But some post online say that it should come to effect right after making the change. Would appreciate if someone can clarify it.</p>