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
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{ 37 comments… read them below or add one }
Icreasing the file handles is a good tip, but 5000 is very low these days. 200000 is more realistic for any modern system.
Also, there’s no need to logout, just edit the /etc/sysctl.conf and then type ‘sysctl -p’ as root.
Thanks,
Tachyon
Does this command work for Debian and does it affect SQUID file descriptor too?
Best Regards?
Maroon,
Yes it works on Debian and all other Linux systems/distros.
how to increase in a Redhat linux server? How to find the location of sysctl.conf file or how to find in which file the limit has been set?
thanks in advance
i tried this on a CentOS (which by the way, i’ve decided the worst linux distribution ever), and it doesn’t seem to work. ulimit -n still says 1024, even after logout, even after reboot.
/etc/sysctl.conf is good for the system-wide amount, but don’t forget that users also need different limits. See /etc/security/limits.conf (Debian, Redhat, SuSE all have it, probably most others as well) to assign specific limits on per-group, per-user, and default basises.
I am running “Red Hat Enterprise Linux ES release 4 (Nahant Update 5)” and followed the instructions above. Like “baka.tom”, I was unable to see the change reflected by typing “ulimit -n”. I don’t know if this is a problem, but it certainly reduces the credibility of this article (unless I screwed up, of course).
baka.tom / jason,
The FAQ has been updated for latest kernel. It should work now. Let me know if you have any more problems.
bourne, thanks for pointing out user level or group level filelimit option.
I appreciate all feedback.
Red Hat configuration requires the following line to be added for /etc/security/limits to work.
in /etc/pam.d/login
session required pam_limits.so
I’m trying to make 8192 on Ubuntu 7.10, adding
* soft nofile 8192
* hard nofile 8192
doesn’t work, but when i do change * to username(lets say root) it applies.
So how to change it system wide?
you could use the following command to check if the given change reflected
#ulimit -n -H
that gives the hard value…
“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. ”
I think 75000 should mean the whole system can support 75000 open files at most , not for per user login.
To clear up any confusion for increasing the limit on Red Hat 5.X systems:
# echo “fs.file-max=70000″ >> /etc/sysctl.conf
# sysctl -p
# echo “* hard nofile 65536″ >> /etc/security/limits.conf
# echo “session required pam_limits.so” >> /etc/pam.d/login
# ulimit -n -H
65536
In summary set your max file descriptors to a number higher than your hard security ‘nofile’ limit to leave room for the OS to run.
Can anyone explain all the attributes in ulimit -a and how it impacts the performance of a system?
In Red hat enterprises linux(RHEL4 and RHEL5) after setting nofile limit we need to do below modification
In /etc/security/limits.conf file added
root soft nofile 5000
root hard nofile 6000
Edit the /etc/pam.d/system-auth, and add this entry:
session required /lib/security/$ISA/pam_limits.so
It perfectly worked me.
After this change open a new terminal and issue ulimit -a.
There you could see the updated file descriptor value for root user.
This is very good. Thanks for the post =)
What is the difference between a hard limit and a soft limit?
Thanks,
Is there any equivalent for MAC OS x (darwin) ??
Hi Francisco,
when I issue “ulimit -n -H” on Mac OS X 10.6, it says “unlimited”. So I guess you don’t have to worry about it.
Dirk
I’m using Linux (Debian Lenny) on a server. I would like to keep my ulimit -n settings.
The values in /etc/security/limits.conf (soft and hard limits) and in /etc/sysctl.conf have been increased.
/etc/pam.d/login constains the “session required pam_limits.so”
I’ve also put the “ulimit -n 50000″ command in .bashrc
… and after logout/login and/or ssh, ulimit -n still returns 1024! What tricky settings also need to be changed? These incoherent and over-complicated version-dependent settings really make linux unusable. I’d rather write code than waste my time on linux configuration files.
In the end, it suddenly worked, without changing anything more. How much time is needed before it’s taken into account? Strange and unreliable…
I have a problem about “too many open file “, i had changed all parameters,
but this problem is exist.
My system have a web application system, that have a dongle, I guess the problem
maybe caused by dongle .
Can you help me , thank you !
Good Day Mate
I was going to leave you in my will for this but the mortgage payments might be to high.
Anyway long story short I run free radius and on a new server i built and it constantly reports “no db handles” if you check with the freeradius forum this is a common problem and is usually met with the kurt reply “figure out whats using all the descriptors”.
I had in my mind I had encountered this problem many years ago and it was a matter of increasing the system handles but just could not track it down.
From your article I found my mysql handles were set at 1024 I increased the soft limit to 5000 and the hl to 10000 and all is well in paradise again. Your bloods worth bottling
Cheers Terry
Hi, Can someone please tell me why the amount of open files increase so rapidly when changing from Single user mode to multi user mode?
More users + More process + More background process == More open files
And what if you run, multi user mode from console, i.e without Windows X? Like for instance, what process/processes run that makes the number on increase SO high….like from 160 to 900 open files????
Excluding operating system process(es), if any application runs on muti user mode and does not close the opened file, then it would create this issue. Please make sure that if any external application(may be your own’s or deployed one) runs on muti user mode and closed all the files it has opened if any.
If you have cPanel, check /etc/profile.d/limits.sh. Although you shouldn’t change it here it’s possibly the root cause of your changes not sticking.
Could you please let me know , while we change the ulimit for root using “ulimit -n” , which is the configuration file in which it reflects.
Thanks, it worked for me on Red Hat Linux 5.
Not working on my centos box.
# su – nginx
# ulimit -Hn
1024
# ulimit -Sn
1024
Try in /etc/security/limits.conf file and at the end of the file add this.
* – nofile
Logout and login again and check ulimit -n
Hi,
Worked in RH 5.
It´s very important to know if you have set the max-files for user xx, you must to start the application with the user xx…. if you are starting with another user, the changes does not effetct.
You could also try
ulimit -n xxxxx now
where xxxxx is the number, e.g. 16384. Worked for me on CentOS 5.7.
Nice one, worked fine for me too on Debian 6.
I am trying to increase ulimit on Ubuntu
even after restarting changes are not reflected
u must edit config file ,if u increase the file descriptor value through the terminal means it shold be a temporary only ,if u want to permanently increase your ulimit mean u have to set the ulimit in config file. . . .