ubuntu 18.04 increase max nu open files

edit user.conf and system.conf

added this line to /etc/systemd/user.conf  and /etc/systemd/system.conf

DefaultLimitNOFILE=65536

Change /etc/security/limits.conf

* hard nofile 65536

* soft nofile 65536

edit  /etc/pam.d/common-session

added this line to /etc/pam.d/common-session and /etc/pam.d/common-session-noninteractive:

session required pam_limits.so