To increase the FD limit for a daemon process running under a headless user on a Ubuntu Linux machine we did following changes in /etc/security/limits.conf soft nofile 10000 hard nofile 10000 We also added session required pam_limits.so in /etc/pam.d/login. The changes got reflected for all the users who logged out and logged in again. Whatever new processes are starting under those users are getting new FD limits. But for the daemon which is running under a headless user the changes are not getting reflected. what is the way by which the changes can be reflected for the daemon which is running under headless user ?