guest            soft    nofile          1000
guest            hard    nofile          2000
-------------------------
# su - guest
$ ulimit -a
core file size    (blocks, -c) 0
data seg size     (kbytes, -d) unlimited
file size       (blocks, -f) unlimited
max locked memory   (kbytes, -l) unlimited
max memory size    (kbytes, -m) unlimited
open files          (-n) 1000
pipe size     (512 bytes, -p) 8
stack size      (kbytes, -s) 8192
cpu time       (seconds, -t) unlimited
max user processes      (-u) 1024
virtual memory    (kbytes, -v) unlimited
$ ulimit -n 2000
$ ulimit -n 
2000
$ ulimit -n 2001
-bash: ulimit: open files: cannot modify limit: Operation not permitted
