Sunday, 28 August 2016

How to compile OpenVpn for Windows from source code

OpenVpn suggests cross-compilation - compiling Windows executables with Unix build toolchain. This can be accomplished either by using Linux/Unix or Cygwin on Windows.

This article demonstrates compiling OpenVpn with Cygwin on Windows.

The first step is to get build scripts from

When cloning OpenVpn repositories to Windows machine, make sure Git client for Windows does not automatically convert Unix-style line endings (LF) in source files into Windows-style line endings (CRLF). If this happens UNIX tools that run in Cygwin will report an error complaining about extra CR characters. So, when cloning, use the following command:

$ git clone --config core.autocrlf=false

Required Cygwin packages are listed here:

Package name Cygwin installer path
diffutils All --> Utils
m4All --> Interpreters
makeAll -> Devel
mingw64-i686-binutilsAll -> Devel
mingw64-i686-gcc-coreAll -> Devel
mingw64-i686-headersAll -> Devel
mingw64-i686-pthreadsAll -> Devel
mingw64-i686-runtimeAll -> Devel
mingw64-x86_64-binutilsAll -> Devel
mingw64-x86_64-gcc-coreAll -> Devel
mingw64-x86_64-headersAll -> Devel
mingw64-x86_64-pthreadsAll -> Devel
mingw64-x86_64-runtimeAll -> Devel
patchAll -> Devel
patchutilsAll -> Devel
perlAll --> Interpreters
unzipAll --> Archive
wgetAll --> Web

Download Perl script man2html and save it as a file with no extensions in /bin directory (C:\cygwin64\bin). Script URL is: If build is run with no having this script, the following error is reported at the output:

checking for man2html... no
configure: error: man2html is required for win32
FATAL: Configure pkcs11-helper

Make sure that man2html's shebang contains correct path to perl. In order to find perl's path in Cygwin we can do the following:

$ which perl

In my case shebang


has to be replaced with:


In order to build x64 version of OpenVpn go to ../OpenVpn/openvpn-build/generic and execute:

$ IMAGEROOT=`pwd`/image-win64 CHOST=x86_64-w64-mingw32 CBUILD=i686-pc-cygwin ./build

A bit about Cygwin

Checking whether some particular package has been installed (e.g. ca-certificates):

$ cygcheck -c ca-certificates
Cygwin Package Information
Package Version Status
ca-certificates 2.9-1 OK

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