Unable to set open files limit via limits.conf

Issue

• Unable to raise the open files limit, either via ulimit command or /etc/security/limits.conf file

  # cat /proc/sys/fs/file-max
  5096000
  
  # cat /proc/sys/fs/file-nr
  4448    0       5096000
  
  # grep limit /etc/pam.d/system-auth
  session     required      pam_limits.so
  
  # egrep -v '^$|^#' /etc/security/limits.conf
  Username           hard    nofile          65536
  Username           soft    nofile          32768
  
  # su Username -lc 'ulimit -n'
  2048
  
  # su - Username
  $ ulimit -n
  2048
  
  $ ulimit -n 4096
  -bash: ulimit: open files: cannot modify limit: Operation not permitted