"Max Open Files" for Working Process

Max open files for working process

As a system administrator: The /etc/security/limits.conf file controls this on most Linux installations; it allows you to set per-user limits. You'll want a line like myuser - nofile 1000.

Within a process: The getrlimit and setrlimit calls control most per-process resource allocation limits. RLIMIT_NOFILE controls the maximum number of file descriptors. You will need appropriate permissions to call it.

Raise number of files a process can open beyond 2^20

Okay, I got it. You can't just set fs.file-max. You also have to set fs.nr_open, which has a default value of 2^20. I also removed the /etc/pam.d/common-session I created and commented out the session required pam_limits.so line in /etc/pam.d/sudo.

Cannot change the maximum open files per process with sysctl

For Ubuntu 17.04. See this solution.

Prior to Ubuntu 17.04:

I don't know why the above settings don't work but it seems you can get the same result by using the /etc/security/limits.conf file.

Set the limit in /etc/security/limits.conf

sudo bash -c "echo '* - nofile 10240' >> /etc/security/limits.conf"

• * means all users. You can replace it by a specific username.
• - means both soft and hard for the type of limit to be enforced. Hard can only be modified by the superuser. Soft can be modified by a non-root user and cannot be superior to hard.
• nofile is the Maximum number of open files parameter.
• 10240 is the new limit.

Reload

Logout and log back in. sudo sysctl -p doesn't seem to be enough to reload.

You can check the new limit with:

ulimit -n

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Tested on Ubuntu 16.04 and CentOS 6. Inspired by this answer.

Max number of open files per process in Linux

There is no issue here.

A pipe has two ends, each gets its own file descriptor.

So, each end of a pipe counts as a file against the limit.

The slight difference between 1024/2 = 512 and 510 is because your process has already opened the files stdin, stdout, and stderr, which counts against the limit.

Increase open files limit for process

After trying to resolve this issue in multiple questions, got it down to the fact that supervisor set's its own file limit on the program. As seen in the comments, you have to use minfds setting in supervisor.

To check to see if it is working you can run a cat /proc/$PID/limits

Which should output the number you set minfds too, in my case 100,000

Max open files            100000               100000               files     

I would like to note that when you go and put into supervisor the minfds you put it in the /etc/supervisor/supervisord.conf as if you put in your programs config file it will do nothing.

Max open files per process

It is clear now.

The ulimit command is build in shell. You can set the maxfiles using ulimit -n command for current shell (and every program which was started from this shell).

10252 files - it was my mistake.. it was 253 max open files when I start my test program from shell (253 + stdin + stdout + stderr = 256).

9469 files - the result of my test program running under Xcode, it seems that Xcode set tha maxfiles before running the program.

ulimit is not system wide setting, thats why to set the system wide value for maxfiles you must use launchctl (the first process in the system, try to 'launchctl limit') or sysctl.

And the answer is 256 files.

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