====== Linux - Files - Change "Open Files Limit" ======

If you are getting error “Too many open files (24)” then your application/command/script is hitting max open file limit allowed by linux. You need to increase open file limit as below:

===== Increase limit =====

==== Per-User Limit ====

Open file **/etc/security/limits.conf**

Paste following towards end:

<file bash /etc/security/limits.conf>
*         hard    nofile      500000
*         soft    nofile      500000
root      hard    nofile      500000
root      soft    nofile      500000
</file>

<WRAP info>
**NOTE:**  500000 is fair number.

  * Once the file is saved, logout and login again.

</WRAP>

----

==== pam-limits ====

This is needed to change limits for daemon processes.

Open **/etc/pam.d/common-session**.

Add following line:

<file bash /etc/pam.d/common-session>
session required pam_limits.so
</file>

----

==== System-Wide Limit ====

Set this higher than user-limit set above.

Open **/etc/sysctl.conf**, and add the following:

<file bash /etc/sysctl.conf>
fs.file-max = 2097152
</file>

Run:

<code bash>
sysctl -p
</code>

<WRAP info>
**NOTE:**  This will increase the **total** number of files that can remain open system-wide.
</WRAP>

----

===== Verify New Limits =====

Use following command to see max limit of file descriptors:

<code bash>
cat /proc/sys/fs/file-max
</code>

returns:

<code bash>
9223372036854775807
</code>

----

==== Hard Limit ====

<code bash>
ulimit -Hn
</code>

returns:

<code bash>
1048576
</code>

----

==== Soft Limit ====

<code bash>
ulimit -Sn
</code>

returns:

<code bash>
1024
</code>

----

===== Check limit for other user =====

<code bash>
su - www-data -c 'ulimit -aHS' -s '/bin/bash'
</code>

<WRAP info>
**NOTE:**  Just replace www-data by the linux username to check limits for that user.
</WRAP>

----

===== Check limits of a running process =====

==== Find process-id (PID) ====

<code bash>
ps aux | grep process-name
</code>

----

==== Check the limit ====

<code bash>
cat /proc/XXX/limits
</code>

<WRAP info>
**NOTE:**  Suppose, XXX is the PID found earlier.

</WRAP>

----