ulimit
shows the per-process maximum. The two files under /proc
shows system-wide numbers.
From ServerFault:
file-max
is the maximum File Descriptors (FD) enforced on a kernel level, which cannot be surpassed by all processes without increasing. The ulimit
is enforced on a process level, which can be less than the file-max
.
From http://www.linuxvox.com/post/what-are-file-max-and-file-nr-linux-kernel-parameters/:
What is the file-max
parameter and what should we tune it to? The linux documentation definition is that file-max
denotes the maximum number of filehandles that the Linux kernel will allocate.
[...]
How do I know if I’m getting close to hitting this limit on my server? Run the command: cat /proc/sys/fs/file-nr
. This will return three values, denote the number of allocated file handles, the number of allocated but unused file handles, and the maximum number of file handles. Note that file-nr
IS NOT a tunable parameter. It is informational only. On my server, this returns: 3488 0 793759
. This means that currently, my server has only allocated 3488 of the 793,759 allocation limit and is in no danger of hitting this limit at this time.