Just upgraded to ubunt 18 and now ulimit -n changes hard and soft limits

[Donald Jones]

I recently upgraded from Ubuntu 14 to 18 and now I can't use ulimit -n to increase the allowed number of files open! This is a change from my previous version of Ubuntu.

Lines from /etc/security/limits.conf
jonesdc hard nofile 100000
jonesdc soft nofile 10000

Setting in /etc/sysctl.conf
# Max open files (system limit)
fs.file-max = 100000

When I first open a terminal if I type
$ulimit -n 1000
then
$ulimit -a
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) 10000
pending signals (-i) 30927
max locked memory (kbytes, -l) 16384
max memory size (kbytes, -m) unlimited
open files (-n) 1000
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) 30927
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited

Now if I type
$ulimit -n 999
and then try again
$ulimit -n 1000
bash: ulimit: open files: cannot modify limit: Operation not permitted

Looking further, it appears that ulimit -n changes both the hard and soft limits
$ulimit -H -a
core file size (blocks, -c) unlimited
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 30927
max locked memory (kbytes, -l) 16384
max memory size (kbytes, -m) unlimited
open files (-n) 999
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) unlimited
cpu time (seconds, -t) unlimited
max user processes (-u) 30927
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited