linux 设置最大打开文件描述符数

短命女 2021-12-24 07:13 693阅读 0赞

# Linux Increase The Maximum Number Of Open Files / File Descriptors (FD) #

How do I increase the maximum number of open files under CentOS Linux? How do I open more file descriptors under Linux?  
  
The ulimit command provides control over the resources available to the shell and/or to processes started by it, on systems that allow such control. The maximum number of open file descriptors displayed with following command (login as the root user).

## Command To List Number Of Open File Descriptors ##

Use the following command command to display maximum number of open file descriptors:  
`cat /proc/sys/fs/file-max`  
Output:

75000

75000 files normal user can have open in single login session. To see the hard and soft values, issue the command as follows:  
`# ulimit -Hn # ulimit -Sn`  
To see the hard and soft values for httpd or oracle user, issue the command as follows:  
`# su - username`  
In this example, su to oracle user, enter:  
`# su - oracle $ ulimit -Hn $ ulimit -Sn`

## System-wide File Descriptors (FD) Limits ##

The number of concurrently open file descriptors throughout the system can be changed via /etc/sysctl.conf file under Linux operating systems.

### The Number Of Maximum Files Was Reached, How Do I Fix This Problem? ###

Many application such as Oracle database or Apache web server needs this range quite higher. So you can increase the maximum number of open files by setting a new value in kernel variable /proc/sys/fs/file-max as follows (login as the root):  
`# sysctl -w fs.file-max=100000`  
Above command forces the limit to 100000 files. You need to edit /etc/sysctl.conf file and put following line so that after reboot the setting will remain as it is:  
`# vi /etc/sysctl.conf`  
Append a config directive as follows:  
`fs.file-max = 100000`  
Save and close the file. Users need to log out and log back in again to changes take effect or just type the following command:  
`# sysctl -p`  
Verify your settings with command:  
`# cat /proc/sys/fs/file-max`  
OR  
`# sysctl fs.file-max`

## User Level FD Limits ##

The above procedure sets system-wide file descriptors (FD) limits. However, you can limit httpd (or any other users) user to specific limits by editing /etc/security/limits.conf file, enter:  
`# vi /etc/security/limits.conf`  
Set httpd user soft and hard limits as follows:  
`httpd soft nofile 4096 httpd hard nofile 10240`  
Save and close the file. To see limits, enter:  
`# su - httpd $ ulimit -Hn $ ulimit -Sn`