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I can use ulimit but I think that only affects my shell session. I want the limit increased for all processes. This is on Red Hat.

countermode
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5 Answers5

37

Justin's answer tells you how to raise the number of open files available total to the whole system. But I think you're asking how to raise the per-user limit, globally. The answer to that is to add the following lines to /etc/security/limits.conf:

*               soft    nofile            2048
*               hard    nofile            2048

(Where the * means all users.)

There's some summary documentation in that file itself and in man limits.conf. This is implemented via the pam_limits.so module which is called for various services configured in /etc/pam.d/.

And, I have to admit, I have no idea where that 1024 default comes from. And believe me, I looked. I even tried without the pam_limits module configured, and it's still there. It must be hard-coded in somewhere, but I'm not exactly sure where.

mattdm
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    Hmm... I set this properly. Exit SSH and come back in and my soft limit is still set to 1024. Is there something I'm missing to make this "active"? Thanks. – Joshua Pinter Aug 06 '15 at 00:29
  • @mattdm - It is worth mention that on some Linux distributions the mentioned file will be under: /etc/limits.conf – Guy Avraham Dec 11 '17 at 20:20
  • yeah, I've been looking to know where 1024 is set as the default. is it compiled into the kernel? – asgs Aug 19 '20 at 14:54
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    additionally we need add `fs.file-max = 65536` in file /etc/sysctl.conf as suggested by RHEL https://access.redhat.com/solutions/2469 and @minhas23 – Santosh Garole Feb 11 '21 at 08:08
  • Potential negative side effects? – MadHatter Feb 03 '22 at 06:05
26

Increase max number of ulimit open file in Linux

1.Step : open the sysctl.conf and add this line fs.file-max = 65536

$ vi /etc/sysctl.conf

add new line and

fs.file-max = 65536

save and exit.

2.Step:

$ vi /etc/security/limits.conf

and add below the mentioned

* soft     nproc          65535
* hard     nproc          65535
* soft     nofile         65535
* hard     nofile         65535

save and exit check max open file ulimit

# ulimit -a

....
open files                      (-n) 65535
Tlacenka
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minhas23
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    sysctl -p or logout->login is required to make changes effective. – Shahid Hussain Aug 13 '20 at 05:24
  • This suggestion to have the per-user limit (i.e., "limits.conf") be the same as the system-wide (kernel, "sysctl") one is a recipe for a single user to lock up the system by using up all available files and leaving nothing to anything else. – Davor Cubranic Mar 18 '21 at 14:59
17

But if you're trying to increase the max number of open files of a service like MariaDB or something else (using systemd) you have to do directly in file .service

/lib/systemd/system/<servicename>.service

Will be something like this:

[Unit]
Description=Some Daemon
After=syslog.target network.target

[Service]
Type=notify
LimitNOFILE=49152
ExecStart=/usr/sbin/somedaemon

[Install]
WantedBy=multi-user.target

The completely answer is here: Increasing nproc for processes launched by systemd on CentOS 7

Matheus Baldasso
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  • This needs to be upvoted, as the ubiquity of `systemd` along with its ongoing changes are increasing across the Linux ecosystem. Although, I would suggest to edit the answer to `cp -r /lib/systemd/system/mariadb.service /etc/systemd/system/` and make the changes to that file, rather than the system-wide service file that's provided by the package. – ILMostro_7 Feb 18 '18 at 03:41
16

According to the article Linux Increase The Maximum Number Of Open Files / File Descriptors (FD), you can increase the open files limit by adding an entry to /etc/sysctl.conf.

Append a config directive as follows:

fs.file-max = 100000

Then save and close the file. Users need to log out and log back in again to changes take effect or they can just type the following command:

# sysctl -p

You can also verify your settings with the command:

# cat /proc/sys/fs/file-max
Justin Ethier
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    I'm skeptical about needing to log out and in again for this particular setting, which is system-wide. (That goes for pretty much everything in sysctl...) – mattdm Mar 09 '11 at 18:10
  • True. You only need a new login session for ulimit-style settings (i.e., `pam_limits`). `sysctl` is instant and at the kernel level. – Davor Cubranic Mar 18 '21 at 14:56
4

SUPLEMENT:

You may find config in different place: /etc/security/limits.d/*.conf

I had to modify it. It didn't work without it. Format is the same as for limits.conf

Waldemar Wosiński
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