number of linux file handles

---Check the default maximum number of file handles in the system, which is 1024 by default
# ulimit -n
1024

----Check how many handles the current process has opened
# lsof -n|awk '{print $2}'|sort|uniq - c|sort -nr|more
131 24204　
57 24244　　
57 24231 ........
where the first column is the number of open handles and the second is the process ID.
You can view the process name based on the ID number.
# ps aef|grep 24204
nginx 24204 24162 99 16:15 ? 00:24:25 /usr/local/nginx/sbin/nginx -s

Linux has hard and soft limits. These two parameters can be set through ulimit. The method is as follows, run the following command as the root user:
# ulimit -HSn 4096 In
the above commands, H specifies the hard size, S specifies the soft size, and n represents the maximum number of open file handles for a single process. Personally, I think it is best not to exceed 4096. After all, the more the number of open file handles, the slower the response time will definitely be. After setting the number of handles, the default value will be restored after the system restarts. If you want to save it permanently, you can modify the .bash_profile file, you can modify /etc/profile and add the above command to the end.
------------------------- -----------------------
lsof -n|awk '{print $2}'|sort|uniq -c|sort -nr|more
lsof: WARNING: can't stat() ext2 file system /noah/baidulinux/V2-0.0.10-opt/etc/mtab (deleted)
      Output information may be incomplete.
lsof: WARNING: can't stat() ext2 file system /noah/baidulinux/V2-0.0.10-opt/etc/nsswitch.conf (deleted)
      Output information may be incomplete.
lsof: WARNING: can't stat() ext2 file system /noah/baidulinux/V2-0.0.10-opt/etc/sudoers (deleted)
      Output information may be incomplete.
   3188 10534
   3180 2779
    522 1670
    434 329
    423 689
     87 21889
     59 16754
     16 659
     15 32311
     11 32315
     11 32313
     11 32312
     10 32317
     10 32316
      9 32314