Increase open files in Ubuntu

Check openfiles 

root#ulimit -a
real-time non-blocking time  (microseconds, -R) unlimited
core file size              (blocks, -c) 0
data seg size               (kbytes, -d) unlimited
scheduling priority                 (-e) 0
file size                   (blocks, -f) unlimited
pending signals                     (-i) 127697
max locked memory           (kbytes, -l) 4096024
max memory size             (kbytes, -m) unlimited
open files                          (-n) 1024
pipe size                (512 bytes, -p) 8
POSIX message queues         (bytes, -q) 819200
real-time priority                  (-r) 0
stack size                  (kbytes, -s) 8192
cpu time                   (seconds, -t) unlimited
max user processes                  (-u) 127697
virtual memory              (kbytes, -v) unlimited
file locks                          (-x) unlimited

root#ulimit -Sn #check soft limit
1024
root#ulimit -Hn #check for hard limit
1048576

Increase Limit for Current session

ulimit -n 200000

Increase per-user limit

Change /etc/security/limits.conf

sudo vim /etc/security/limits.conf
root   soft     nproc          65535
root   hard     nproc          65535
root   soft     nofile         65535
root   hard     nofile         65535
*      soft     nproc          200000
*      hard     nproc          200000
*      soft     nofile         200000
*      hard     nofile         200000

Change pam.d

sudo vim /etc/pam.d/common-session
session required pam_limits.so

Increase system-wide limit

vim /etc/sysctl.conf 
fs.file-max = 2097152

root#sysctl -p

 reboot