Max files too low


Max files too low - you may want to increase it

How to increase it?

I read this information but it tells me nothing:

Max files allowed = %ld
Logs the nfiles currently configured.
Max files too low - you may want to increase it
If nfiles is <1024, the pbs_comm daemon emits the message. If nfiles configured is <100, the startup aborts.
Usually nfiles must be configured to allow the number of connections (usually the number of MoMs) the
pbs_comm process is going to handle.

Anyone can remark in this topic?

Hi, I am interested in an answer as well, please explain what is this configuration effects, how to change it and when.


u can increase the nfiles limit using ulimit command before starting pbs_comm, or u can make a permanent change using systemctl… see this page for help: How to Increase Number of Open Files Limit in Linux

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Thanks @subhasisb , can you please explain what are the instructions as to decide which value should we set it to?

Is it based on number of Moms? Number of jobs? etc.


pbs_comm is a broker - it is the component that mediates messages between the server/mom and between moms. It consumes one file descriptor per tcp connection. These endpoints (server, moms) that connect to the same pbs_comm consumes one fd, each. So, the number of moms primarily dictate the value of nfiles u need for comm.

Of course, some fds are already consumed by the pbs_comm process in libraries, configuration files etc (we can keep aside a hundred for that). Thus, if you have 2000 moms, then you might want to set nfiles to something like 2500…

Thank you @subhasisb thats very helpful information

I also encountered the problem of “Max files allowed = 1024, Max files too low - you may want to increase it”
All of the following operations are performed by root

My steps are as follows:
(1)The default ulimit -n of my OS is 1024.
So when the PBS service is started, PBS_mom, pbs_sched,pbs_serveres all prompt as follows (no pbs_comm):

			01/07/2022 18:01:16;0d80;pbs_mom;TPP;pbs_mom(Main Thread);Max files allowed = 1024
			01/07/2022 18:01:16;0c06;pbs_mom;TPP;pbs_mom(Main Thread);Max files too low - you may want to increase it.
			01/07/2022 18:01:36;0d80;pbs_sched;TPP;pbs_sched(Main Thread);Max files allowed = 1024
			01/07/2022 18:01:36;0c06;pbs_sched;TPP;pbs_sched(Main Thread);Max files too low - you may want to increase it.
			01/07/2022 18:02:02;0d80;Server@cf-poc-master;TPP;Server@cf-poc-master(Main Thread);Max files allowed = 1024
			01/07/2022 18:02:02;0c06;Server@cf-poc-master;TPP;Server@cf-poc-master(Main Thread);Max files too low - you may want to increase it.

(2)Then I change ulimit -n 102400 in /etc/security/limits.conf:
root soft nofile 102400
root hard nofile 102400

(3)Then restart the machine and confirm that the modification takes effect
command “ulimit -n” output 102400

But, when PBS service starts again, pbs_mom, pbs_sched and pbs_server(except pbs_comm) still report warning mean that 1024 too low like above,
then I try command “ulimit -n 102400” in the current login shell, it still no effect


Should I modify ulimit in the pbs’s systemd service conf file,or by systemctl, or there maybe some conf in pbs overwrite the OS config?

Looking forward to your reply, thank you!