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Distcc mozilla tutorial

What is this?

This is a tutorial to get distcc to compile Mozilla Firefox on Windows using cygwin.


  1. Window machines. For distcc to be of any use, there should be at least 2 machines
  2. Cygwin. You will need gcc to build distcc. We build using gcc-3.4.4
  3. Mozilla requirements
  4. Patience

Building distcc

Checkout, build, and install the distcc source

svn co svn://
cd trunk && ./configure && make && make install

Checkout the Mozilla source. If you are using the latest version of trunk, than you are fine. If you are building or below, you need to apply a silly patch.


Currently, distcc does not transmit debug .pdb files (i.e., it can only send back one file). So you cannot currently do a debug build. Here is a sample MOZCONFIG file. All you need to do is modify the object directory (MOZ_OBJDIR).

Note the last line, which is required for any MOZCONFIG file that wants to build using distcc.

mk_add_options MOZ_OBJDIR=/cygdrive/c/home/cesar/mozobj
ac_add_options --enable-application=browser
ac_add_options --enable-optimize
ac_add_options --disable-debug
ac_add_options --enable-debugger-info-modules=no
mk_add_options MOZ_CO_PROJECT=browser
mk_add_options MOZ_MAKE_FLAGS="CC='distcc cl' CXX='distcc cl' -j4"

-j4 is quite important. According to the man page, you should set the number of jobs equal to the number of all cpus (or cores) + 2.


The only required environment variable is DISTCC_CL_HOSTS, which contains a space delimited list of all slave machines. You must set this variable on the master machine (the machine that contains the source code).

export DISTCC_CL_HOSTS="localhost"

Distcc Daemon

Start the distcc daemon. The only thing you need to change is who is allowed to use the daemon. You can use a space-delimited list of IP addresses, or specify the CIDR mask of an entire subnet.

distccd --allow '' --daemon

Compile Mozilla

You should now be able to compile Mozilla. You won't notice distributing immediately. But you can monitor the progress using the distcc-text or distcc-gnome utility, or using the 'Task Manager'. Sometimes, mozilla forces -j1 in some directories. So be prepared for that.


If you feel that these instructions are poorly written, or are having trouble using distcc to compile mozilla because something is unclear, please leave a message in the discussion page. I appreciate any feedback (good/bad) in hopes of improving this documentation.

You do not have to leave a contact or your name.