How do I change the number of open files limit in Linux? [closed]

Question

When running my application I sometimes get an error about too many files open.

Running ulimit -a reports that the limit is 1024. How do I increase the limit above 1024?

Edit ulimit -n 2048 results in a permission error.

Blackout

see also:unix.stackexchange.com/a/8949/231660 – Exciter

I just went through this on Centos 7 (same on RHEL) and made a blog post covering it because I had so much trouble even with all these posts: coding-stream-of-consciousness.com/2018/12/21/…. Often along with open files, you need to increase nproc which actually resides in multiple settings files... and if you use systemd/systemctl that has its own separate settings. It's kind of nuts. – Countersignature

If you are using VSCode on linux this workaround might help: https://mcmap.net/q/108363/-nodemon-error-quot-system-limit-for-number-of-file-watchers-reached-quot – Heteronym

a-bars closed this question while linus on GeeksForGeeks.com trying to figure this out also – Roderich

Answer 1

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.

set rlim_fd_max = 166384
set rlim_fd_cur = 8192

On OS X, this same data must be set in /etc/sysctl.conf.

kern.maxfilesperproc=166384
kern.maxfiles=8192

Under Linux, these settings are often in /etc/security/limits.conf.

There are two kinds of limits:

• soft limits are simply the currently enforced limits
• hard limits mark the maximum value which cannot be exceeded by setting a soft limit

Soft limits could be set by any user while hard limits are changeable only by root. Limits are a property of a process. They are inherited when a child process is created so system-wide limits should be set during the system initialization in init scripts and user limits should be set during user login for example by using pam_limits.

There are often defaults set when the machine boots. So, even though you may reset your ulimit in an individual shell, you may find that it resets back to the previous value on reboot. You may want to grep your boot scripts for the existence ulimit commands if you want to change the default.

Odrick

can you tell me how to use this in windows? – Ssm

@Odrick I can change it as 2048 but not as 4500 why? see this – Run

@GaneshKrishnan what to add in the linux files that you have mentioned? – Isoprene

@Ssm Windows don’t have any ulimit. You must specify what you are using (e.g. WSL, Cygwin). – Razorback

Answer 2

If you are using Linux and you got the permission error, you will need to raise the allowed limit in the /etc/limits.conf or /etc/security/limits.conf file (where the file is located depends on your specific Linux distribution).

For example to allow anyone on the machine to raise their number of open files up to 10000 add the line to the limits.conf file.

* hard nofile 10000

Then logout and relogin to your system and you should be able to do:

ulimit -n 10000

without a permission error.

Blim

NOTE: Wildcard does not apply to root user. You have to specify root hard nofile 10000 if you want to adjust the root limit. – Mozzarella

@JoshPinter Haha, I just spent the past 3 hours or so going through every single tutorial on how to change the ulimit and finally found out I am logged in as root. That's why I kept seeing the 1024 in ulimit -a. I changed the wildcare, and added a * inside limits.conf. All is good now, (im using ssh keys don't worry :P) -- Thank you!!! – Fancyfree

@NiCkNewman I'm glad you're laughing about it! That's a good trait in a programmer/sysops person. I did the same thing and wasn't so jovial. Glad it helped! :) – Mozzarella

SUPLEMENT: You may find also a config in this dir: /etc/security/limits.d/. – Jagatai

I've opened /etc/security/limits.conf for the first time and noticed that everything is commented out there. What is the default value of "hard nofile" then? – Semiyearly

I am using Ubuntu-18.04, I found that after making the changes in /etc/security/limits.conf , I had to RESTART the system then it worked. – Comfrey

Answer 3

1) Add the following line to /etc/security/limits.conf

webuser hard nofile 64000

then login as webuser

su - webuser

2) Edit following two files for webuser

append .bashrc and .bash_profile file by running

echo "ulimit -n 64000" >> .bashrc ; echo "ulimit -n 64000" >> .bash_profile

3) Log out, then log back in and verify that the changes have been made correctly:

$ ulimit -a | grep open
open files                      (-n) 64000

Thats it and them boom, boom boom.

Embrey

If you get change your line in limits.conf from 'hard' to 'soft' it should become the new default and not require changes to bash profiles. – Protectionist

Seems you are repeating an extra steps. Setting limits alone will do the same as the profile, but across all sessions. – Hamadryad

Answer 4

If some of your services are balking into ulimits, it's sometimes easier to put appropriate commands into service's init-script. For example, when Apache is reporting

[alert] (11)Resource temporarily unavailable: apr_thread_create: unable to create worker thread

Try to put ulimit -s unlimited into /etc/init.d/httpd. This does not require a server reboot.

Morehouse