By default, each user is limited maximum number of open files to 1024. Sometimes this value might be insufficient, e.g., you are running peer-to-peer applications on the host. If you want to see the current value, run ulimit -n or ulimit -a to see all limits. Anyway, you should get error messages as follow whenever the limit is not enough.

Too many open files

All limits are specified in /etc/security/limits.conf. In order to change maximum number of open files for each users, add below line in that file.

*               hard    nofile          4096

* means all users will have hard limits of max open files as 4096.

Tags: linux, ulimit