Open file limits

Jules Agee julesa at
Tue Jul 6 15:10:58 EDT 2004

AJ wrote:
> Hi, Can anyone share experiences with running out of open files on
> Linux? I am using a 2.4.26 kernel, and the system wide open file
> limit is rather large. Do I need to set anything other than this? The
> default limit of 1024 is in effect for both cyrus and root.
> Thanks. AJ

# cat /proc/sys/fs/file-nr
25301   1092    65532

The three numbers represent allocated filehandles, free fh, and max fh. 
If cyrus needs more filehandles than max fh, the kernel will refuse to 
give it any more, and you will get a "too many open files" error. The 
above numbers are from a system with 375 concurrent imapd processes. If 
allocated fh starts getting close to max fh, you need to increase the max.

The RedHat default max is pretty low (8192), at least it was when I was 
running Cyrus on RedHat boxes (RH 7.2, 7.3). Maybe they've changed the 
default since then. On Debian Woody systems, you have a little more room 
by default (32768). This will all become moot with the 2.6 kernel, but 
I'm not ready to run 2.6 on my production mail server yet. :-)

Add something like this to a boot script:
echo 65536 > /proc/sys/fs/file-max


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Jules Agee
System Administrator
Pacific Coast Feather Co.
julesa at      x284
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