max open files reached

Roman Neuhauser neuhauser at
Wed Jun 4 07:54:48 PDT 2003

# jackstone at / 2003-06-04 09:30:36 -0500:
> At 03:29 PM 6.4.2003 +0200, Roman Neuhauser wrote:
> >I have a script run by periodic(8) in the daily batch that is supposed
> >to backup all databases from the local MySQL server using
> >mysqlhostcopy(1). It used to run fine for a few months, but has
> >been failing consistently with ENFILE (23) lately.
> >
> >The box is an Intel Celeron 533 (or some such) with 128 MB RAM. These
> >are all the related sysctl knobs I could find. This is as of 20:40, so
> >the value of kern.openfiles is reasonable.
> >
> >roman at ishtar ~ 1001:0 > sysctl -a kern|grep files
> >kern.maxfiles: 2024
> >kern.maxfilesperproc: 1821
> >kern.openfiles: 512
> >
> >I've cranked the kern.maxfiles value to 4096, and the backup has run to
> >completion again, but am I risking anything? I mean, the fd's cost
> >memory, is there any potential for problems?
> >
> I don't see any problems with raising to 4096 as 2024 looks awful low. Most
> of mine run 12000+ and the lowest at about 8000. I do have more CPU and RAM
> in the equation. What do you have the "maxusers" set to in your kernel? I
> have found this will usually take care of making the correct calculations
> for the max files. A setting of "0" is good for later versions of FBSD.
> Don't remember what version changed this & you didn't mention your version.

    it was @(#)FreeBSD 4.7-STABLE #0: Thu Dec 26 19:32:12 CET 2002 till
    ten minutes ago, and is 4.8-STABLE now. both kernels have maxusers
    set to 0:

    roman at ishtar ~ 1014:0 > strings /kernel|grep -E ^___maxusers    
    ___maxusers     0
    roman at ishtar ~ 1015:0 > strings /kernel.old|grep -E ^___maxusers
    ___maxusers     0

    That looks like the old value was indeed decided by the kernel
    itself (it's 4072 on my PC w/ 256MB and 10216 on a box that has
> Otherwise, you'll need to set the max files in your /boot/loader.conf so
> they stay up at the 4096, or whatever workable level is good for you.

    I've put it in sysctl.conf, works fine.

    Thanks for the reply.

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