BIND: Max open files (1024) is smaller than max sockets (4096) Error and Solution

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While going though my logs I found that BIND9 on Debian version 5.x is giving a warning which read as follows:

max open files (1024) is smaller than max sockets (4096)

How do I fix this problem?

The “open files is smaller than max sockets” problem is kernel bug which is already fixed in 2.6.28. Linux kernel returns EPERM when RLIMIT_NOFILE is set to RLIM_INFINITY. To fix this issue update your Linux kernel using yum or apt-get command.
# yum update
OR
# apt-get update
# apt-get upgrade
Reboot the server. Verify error is not reported after boot:
# tail -f /var/log/messages

See kernel bug # 461458 and 515673 for more information.

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.

9 comment

  2. how to fix on debian lenny 5.0 ( 2.6.26-2-686):

    # vim /etc/default/bind9

    add “-S 1024” to “OPTIONS” line:

    # run resolvconf?
RESOLVCONF=yes

# startup options for the server
OPTIONS="-u bind -S 1024"

    restart bind:
    # /etc/init.d/bind9 restart

    check for errors:
    # cat /var/log/syslog

  3. ooops :)

    # vim /etc/default/bind9

    add “-S 1024″ to “OPTIONS” line:

    # run resolvconf?
    RESOLVCONF=yes

    # startup options for the server
    OPTIONS="-u bind -S 1024"

  6. There’s another way of fixing it on Linux:

    At the beginning of the “start” section of /etc/init.d/bind9 add i.e.:

    ulimit -HSn 8192

    so you have some extra, spare file descriptors for the whole process,
    and then restart the bind using:

    # /etc/init.d/bind9 restart

    and voila, log reads:

    […]
    named[19060]: using up to 4096 sockets
    […]

  7. The preceding “ulimit -HSn 8192” command might better go in /etc/default/bind9 on debian to keep package updates (ie. changed config files) a little smoother.

  8. If you are using Centos or redhat, edit /etc/sysconfig/named and at the bottom, at,

    OPTIONS=”-4 -S 1024″

    It think the author’s claim of upgrading the kernel it’s false and can be dangers. I got a vmware application runnning on the host, upgrading the kernel can simply break it

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