Setting ulimit

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1

Hi,
Is there any native way to set ulimit for a coreos build?
I’m investigating using it to run a docker application that requires a signicant amount of open files.
I know i can set the file limit in the container via --ulimit nofile=262144:262144 but my coreos image shows a file limit
open files (-n) 1024

Thanks

3

Thanks Vladislav, is that applicable to coreos? that file (or any of the standard directories) doesn’t exist on the test instances that I have

4

I tried setting
cat /etc/systemd/system.conf
[manager]
DefaultLimitNOFILE=65536

but ulimit -a still shows 1024 so i assume that coreos pulls that value from elsewhere

1 Like
6

I’ve just tried configuring Butane to create a systemoverrides bash file

storage:
  files:
    - path: /etc/propertyoverride.sh
      mode: 0744
      contents:
        inline: |
          #!/bin/bash         
          echo '* soft nofile 4096' >> /etc/security/limits.conf
          echo '* hard nofile 8192' >> /etc/security/limits.conf
          echo 'root soft nofile 4096' >> /etc/security/limits.conf
          echo 'root hard nofile 8192' >> /etc/security/limits.conf

And then a oneshot systemd unit file

systemd:
  units:
    - name: set-systemoverrides.service
      enabled: true
      contents: |
        [Unit]
        Description=Setup system parameter overrides

        [Service]
        Type=oneshot
        ExecStart=bash /etc/propertyoverride.sh

        [Install]
        WantedBy=multi-user.target

It feels a bit hacky but seems to work ok

7

That is the soft limit.

But you have set the hard limit with DefaultLimitNOFILE=65536 I think.

You can see the hard limit with ulimit -aH.

Usually an app with set the soft limit higher when it runs.

8

One can see the options for ulimit by using man ulimit which brings up the man page for the bash built-ins, then search for ulimit.

ulimit -a displays all limits that are set; and as already mention ulinit -aH gives the hard limits.
for my user I see

open files                          (-n) 1024

and

open files                          (-n) 1048576

respectively.

9

I think this can be improved. Ignition/Butane do support appending to a file:

storage:
  files:
    - path: /etc/security/limits.conf
      mode: 0644
      append:
        - inline: |
            * soft nofile 4096
            * hard nofile 8192
            root soft nofile 4096
            root hard nofile 8192
2 Likes
10

That worked great thanks!

1 Like