Allegro NFS Server for Microsoft Windows, written in Common Lisp
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Allegro NFS Server for Windows

Table of contents


The repo contains the source code for Allegro® NFS Server for Microsoft Windows®, written in Allegro Common Lisp. The author is Ahmon Dancy, with help from Elliott Johnson, Kevin Layer, and Jeremiah Rothschild.

It was inspired by our dissatisfaction with current free and commercial NFS Servers for Windows available on the market, and the incredible technical difficulties we faced in configuring them on Windows.

It runs on Microsoft Windows 7 and later (including Windows 8 and Server 2008 and 2012).

This source code is licensed under the terms of the Lisp Lesser GNU Public License, known as the LLGPL. The LLGPL consists of a preamble and the LGPL. Where these conflict, the preamble takes precedence. This project is referenced in the preamble as the LIBRARY.


This software is open source, however some of the tools needed to build it are not. You can purchase a supported binary copy of this software or download an evaluation version from

To build this software, you need Cygwin (for GNU make) and Allegro Common Lisp 10.0 (32-bit, non-SMP). The installer is written in NSIS.

To build:

make all

To install:

make install

The install step expects that cygwin has C:\ mounted as /c. It is also possible to build an installer via:

make installer

This will produce an exe file that can be used to install.


See the documentation for more information on how to configure nfs.

Also see doc/configuration.txt.

Once your exports are configured it's possible to mount them. Please consult your client platform's documentation on how to mount the exported NFS shares.

Release Notes


Changes in this section will appear in the next release of Allegro NFS.

Version 6.2 [7 December, 2016]

  • Fix: use an Allegro CL build that fixes a GC leak, which could result in the server process growing until it runs out of space. This bug was only present in version 6.1.

  • Fix: handle "tcp connection reset" errors, which previously made the server die and require manual restart. They are now ignored.

  • For silent installs (/S given to installer) do not start the configuration program at the end.

  • Directory entries are now returned in the order in which Windows returns them. Previously, directory listing were reversed.

  • The server can now detect when files or directories are renamed externally (i.e., not by an NFS client) and update its cache accordingly. Previously it could get into a confused state if files or directories were renamed externally.

Version 6.1 [21 Jul, 2016]

  • Log possible conflicting NFS server running if an existing (aka system) portmapper is detected.

  • Fix: adjust the nfsd error handling so that certain errors do not cause the service to exit, and return reasonable errors to the client.

  • Fix: adjustments in heap placement for Windows 10. There should be fewer problems with service startup due to ASLR.

  • Fix: increased general client compatibility.

  • Fix: improved compatibility with the Windows Services For Unix (SFU) NFS client.

  • Fix: don't display configuration window until config has been loaded. This will help avoid confusion in cases where the NFS server is busy and it takes a while to get a response from it.

  • Fix: handle full filesystem errors, returning the proper ENOSPC error code to the client.

  • Fix: allow statfs and fsstat procedures on filenames (as opposed to a directories).

Version 6.0 [27 Mar, 2015]

  • Added support for persistent file handles for files on NTFS volumes. This means that you can restart Allegro NFS or the machine that it is running on and not suffer stale NFS file handle errors on the client. Non-NTFS files (or inaccessible files on NTFS volumes) still use non-persistent file handles are still subject to stable NFS file handle errors after restarts.

  • Allow control over how long file attribute are cached through the configuration GUI. See the "File attribute caching time" setting in the Global tab of the Allegro NFS configuration program.

  • Configuration for "Host lists" allows host names in the "New address" field. When loading the configuration and resolving the host names, users will be warned if the conversion of saved host names fails, and the host name will be ignored.

  • When constructing file mode bits for reporting to an NFS client, Allegro NFS uses the filename extension to determine if the file should have the executable (x) bits set. Previously only files with extension .exe, .com, or .bat were marked executable. This list is now adjustable by modifying nfs.cfg and adding an entry for executable-types. This operation should only be performed by advanced users.

  • File attributes are cached for a maximum of 5 seconds. Prior to this change, the expiration for cached file attributes would be extended each time they were accessed. This could be a problem in the following scenario:

    • an NFS client is repeatedly calling stat() on a file to see if its attributes had changed, and

    • the attributes of the file were altered outside of Allegro NFS's knowledge.

    In this case the new file attributes would never be returned, at least not until the client stopped probing for a sufficiently long time.

  • Use higher precision timestamps in log messages, enabled via an option on the debug tab.

  • Change default statfs blocksize from 8192 to 512. This improves compatibility with some broken NFS clients which do not work properly if the blocksize is not 512.

  • Minor change to showmount output.

  • General performance and stability improvements.

  • Fix: input validation bugs in the Allegro NFS configuration program.

  • Fix: mounting a subdirectory of an export. For example, if you have an export named "/export" which has a subdirectory named "files", then mounting servername:/export/files from an NFS client now works properly.

  • Fix: file and directory changes on the server weren't seen by some clients. This would make files appear to be static even though they had been modified on the server.

  • Fix: some previously invisible files are now seen by clients, such as in the roots of filesystems, System Volume Information and pagefile.sys.

Version 5.1 [1 Aug, 2011]

  • performance improvements
  • minor license changes
  • new: toggling of response to showmount requests.
  • new: configurable log rotation. Defaults to previous behavior.
  • new: directory and file caching duration is now configurable.
  • fix: interoperability fixes with VMware ESXi.
  • fix: hanging of the server and 100% cpu usage problems are removed.
  • fix: moving the error log into the install directory.
  • fix: proper locking around exports and logging operations.
  • small modifications to icons.

Version 5.0 [22 Feb, 2010]

  • performance improvements
  • better support Windows Vista/7
  • new: support for symbolic links
  • new: support for international filenames (UTF-8)
  • new: support for mount protocol version 2
  • new console separate from service, that is shows log info
  • added NLM and NSM debug options
  • add date to timestamp logging
  • New option *nfs-set-mtime-on-write* allows users to work around Windows' funny behavior with respect to file modification times. Normally Windows does not update the mtime on a file until the file is closed. Since Allegro NFS keeps a file open while it is actively being written-to, a Windows program periodically checking the mtime of the file will not be able to tell that the file is actually being modified until the file is closed. Updating the mtime during every write access suffers about a 10% penality so the option is disabled by default.
  • improvements to hard link support
  • better compatibility between UNIX and Windows-style locking
  • improved interoperatibility with several UNIX clients
  • many other small improvements and fixes

Version 4.5 [20 June, 2007]

  • Windows Vista Support
  • Many interoperability fixes and bug fixes
  • Improved locking support
  • NLM and NSM port numbers can now be set manually

Version 4.4 [29 Aug, 2006]

  • NFS lock support
  • Bug fixes
  • Enhanced debugging

Version 4.3 [27 Oct, 2005]

  • Installs on systems with Windows Data Execution Prevention (DEP) turned on
  • allow specification of mountd port number for dealing with firewall issues
  • made mountd subprocess more robust in the face of malformed RPC messages
  • adjusted the logging of some "normal" error conditions so they look less alarming
  • better performance
  • bug fixes

Version 4.0 [10 Aug, 2005]

  • NFS protocol V3 support
  • large file support
  • better performance
  • Hard link creation support

Version 3.0 [22 Apr, 2004]

  • handle UNC pathnames
  • added "use system portmapper" option
  • improved performance

Version 2.0 [24 Feb, 2004]

  • new configuration utility

Version 1.1.4 [3 Jul, 2003]

  • improved interoperability with some clients
  • configuration option for altering mode bits

Version 1.1.3 [21 Mar, 2003]

  • bug fixes

Version 1.1.1 [23 Jan, 2003]

  • Improvements of handling the NFS services

Version 1.0.36 [23 Sep, 2002]

  • bug fixes

Version 1.0.33 [27 Feb, 2002]

  • initial release

Implementation Notes

The following files in the doc subdirectory have various information related to understanding how to debug and understand the product:

  • access-control.txt - info on controlling access to the nfs server
  • configuration.txt - info on configuration
  • debugging.txt - notes on debugging
  • notes.txt - implementation notes
  • profiling.txt - how to profile the server
  • testing.txt - information on testing
  • todo.txt - old and new todo information.