ulimit -a 于file-max 有什么关系??

Hunterforpig

root@sky:~# ulimit -a
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
file size (blocks, -f) unlimited
max locked memory (kbytes, -l) 32
max memory size (kbytes, -m) unlimited
open files (-n) 1024
pipe size (512 bytes, -p) 8
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 4031
virtual memory (kbytes, -v) unlimited

root@sky:~# cat /proc/sys/fs/file-max
50355
当unlimit -a 时显示open files最多为1024
而系统的file-max为5w
请问这两个地方为什么有这种差异,用户能够open files的数值为多少
如何设置为系统默认每个用户就能开到5w
谢谢!!