HowTo: Increase The Maximum Number Of Open Files / File Descriptors (FD)

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Sometimes we will get the error message is like “too many files open“, it is because of you have reached the limits of opened file, You could always try doing a ulimit -n 2048. This will only reset the limit for your current shell and the number you specify must not exceed the hard limit.

Each operating system has a different hard limit setup in a configuration file. For instance, the hard open file limit on Solaris can be set on boot from /etc/system.

[anand@planetcure ~]$ cat /proc/sys/fs/file-max
172214

This show the maxmimum number of opened files for the single user, you can also use the below commad.

# ulimit -Hn
# ulimit -Sn

We can set this as System-wide and userlevel, for Global user configuration we can use /etc/sysctl.conf file under Linux operating systems. 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):

System-wide File Descriptors (FD) Limits

# sysctl -w fs.file-max=100000

The command allows to extend the new limit as 100000. You need to append the variable “fs.file-max = 100000” in the file /etc/sysctl.conf for the permanent set. It won’t be change after the reboot.

#sysctl -p

Verify by using below command

#sysctl fs.file-max

User-level File Descriptors (FD) Limits

Some of the case we need to specify the different level of setting for the particular users. This will override the sysetm wide settings and give the new limits for the users.

To specific limits by editing /etc/security/limits.conf file, we can all so use this file for all user limits

For apache:

httpd soft nofile 1024
httpd hard nofile 2048

All user limits

* soft nofile 1024
* hard nofile 2048

Save and close the file. You have to re-login to the console to get the new value.

su httpd -c "ulimit -Hn"
su httpd -c "ulimit -Sn"
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