Each user’s processes can be resource restricted. This helps prevent malicious users from consuming excessive resources of a system. Resources items include the number of open files and memory.
As root, edit
/etc/security/limits.conf. You can add a record that will change limit
based on user or group, resource item, and limit type (soft vs hard).
As the user, you can change your own limits using the
As the user, run
ulimit -a to see your current limits.
If you see the error
Too many open files then the process has reached the system limit of number of open files.
To see which files are open run
lsof which lists open files.
An alternative is to run
ls -l /proc/PID/fd/, where PID is the process ID.