Increasing The Linux NFS Mount Limit
====================================

Shanker Balan
http://shankerbalan.com/

Changelog:

Fri Apr 19 10:59:11 IST 2002
- Initial commit

The Linux kernel imposes a limit on the number of anonymous file mounts that it
can handle. The default mount limit as of kernel 2.4.17 is 256. Conventional
knowledge says that if you need so many NFS mounts, then you are doing
something wrong. Anyways, since you are reading this, I assume that you have a
requirement for doing more than 256 NFS mounts.

To increase the NFS mount limit, You need to patch the kernel and the user
space "mount" utils as follows:

Patch the kernel to support more than 256 NFS Mounts
====================================================

To make things much simpler, RedHat kernel patches are available here:
http://people.redhat.com/zaitcev/tmp/

Download "linux-2.4.9-unmaj-8.diff" patch it against the latest RedHat kernel
release (kernel-2.4.9-31). Compile and install the patched kernel. See
http://www.tldp.org/HOWTO/Kernel-HOWTO.html for patching, compiling and
installation instructions.

This patched kernel will let you do a maximum of 1279 simultaneous NFS mounts
on your Linux box.

Change "mount" tools
=====================

Download, recompile and upgrade to "mount-2.11g-6.src.rpm" from
http://people.redhat.com/zaitcev/tmp/

The new "mount" tools implements a "insecure" mount option. This allows for
mounting NFS shares using ports greater than 1024. With this version of mount,
it should be possible to mount up to a maximum of 1279 mounts.

Use the "nores" option to force NFS mounts over unreserved ports like this:

	root# mount -t nfs nfs:/path/to/share /mnt/nfs -o nores

Hopefully, at some point the patches for increasing the mount limit should make
it into the Linux kernel and the mount tools.

FreeBSD does not have such limitations.